,transcriber note ,text emphasis is displayed as3 ,italic and ,bold4 ,in most tables and where numbers with fractions are used for sizing items1 the symbols 1 1 and were used4 ,otherwise1 whole and fractional numbers are displayed as #a-e_/h ,,fireplaces and ,,chimneys ,,farmers' ,,bulletin ,,no4 #ahhi ,u4,s4 ,,department of ,,agriculture ,,that ,,the ,,word ,,hearth is synonymous with home in many languages is not surprising since much of the enjoyment of home and camp life centers about an open fire4 ,in mild climates a properly built fireplace will heat a single room1 and when equipped with a convection heater will also heat a second room on the same floor or an upper floor4 ,in colder climates it is a useful adjunct to other heating systems if provided with a damper4 ,this bulletin is intended to give the householder and prospective builder1 especially the farmer who might superintend the construction of his home1 a working knowledge of the principles to be observed in planning and building fireplaces and chimneys4 ,these principles1 if observed1 will make the structures useful and satisfactory and insure their safety4 ,safe fireplaces and chimneys that function properly can be built by applying the principles given in this bulletin1 but a good chimney will not last indefinitely without proper care and repair4 ,fireplaces and chimneys1 being conspicuous architectural features1 should be pleasing in appearance and conform with the general design of the building and its surroundings4 ,this bulletin supersedes ,farmers' ,bulletin #afdi1 ,construction of ,chimneys and ,fireplaces4 ,washington1 ,d4 ,c4 ,issued ,december1 #aida ,,fireplaces ,,and ,,chimneys ,by ,arthur ,h4 ,senner1 mechanical engineer1 and ,thomas ,a4 ,h4 ,miller1 agricultural engineer4 ,division of ,farm ,structure ,research1 ,bureau of ,agricultural ,chemistry and ,engineering ,,contents ,page ,chimneys #b ,design #b ,construction #g ,estimating brick #ah ,smoke test #ah ,cleaning and repairing flues #ai ,fireplaces #bb ,characteristics #bb ,modified fireplaces #bd ,selecting a fireplace #bg ,construction #cd ,dimensions #ce ,cost estimate #dc ,smoky fireplaces #de ,outdoor fireplaces #df ,types #dg ,obtaining plans #dh ,construction #dh ,operation #ea ,barbecue pits #ea ,dutch ovens #ea ,,fireplaces ,,and ,,chimneys should provide a safe place for an open fire and a flue for draft to expel smoke from the fire passage to the open air4 ,they must be properly designed and constructed 7fig4 #a7 if good performance and protection against fire are to be obtained4 ,illustration3 ,figure #a4--;,a properly designed and well-built chimney that provides ample draft and protection against fire4 ,,chimneys ,,design ,solid masonry is the most satisfactory and safest material to use for chimneys and fireplaces4 ,if a chimney fire occurs1 the safety of the building may be dependent on the soundness of the flue walls 7fig4 #b74 ,cracked and leaky flues not only are inefficient1 destroying the draft as well as permitting smoke and gases to pass into adjacent rooms1 but are a dangerous fire hazard4 ,the chimney as known today was developed about #fjj years ago4 ,experience has shown that the satisfactory performance of a chimney flue is determined by its size1 direction1 shape1 height1 tightness1 and smoothness4 ,draft ,the draft of a chimney is the current of air created by the difference in pressure resulting from variation in weight between the relatively hot gases in the flue and the cooler outside air4 ,the strength or intensity of the draft depends1 for the most part1 on the height of the chimney1 and the temperature difference between the chimney gases and the outside atmosphere4 ,the draft is not so good in summer as in winter because the difference in temperature between the outside air and the gases in the flue is less4 ,a very common error in chimney design is failure to distinguish between the size of the flue required for free passage of the volume of smoke from a given amount of fuel and that which1 with proper height1 will produce the required draft4 ,a chimney may be high enough 7fig4 #c71 yet have an area too small to expel the volume of smoke2 or the size may be ample 7fig4 #d7 but the height not great enough to produce a strong draft4 ,either fault or a combination of the two will result in unsatisfactory service4 ,flue ,sites ,the dimensions of a flue for adequate draft depend principally on the grate area and type of heating plant #a and on the kind of fuel to be burned1 both of which should be determined before construction is begun4 ,if a chimney is found to be inadequate the only method of improving it1 short of reconstruction1 is to increase its height4 ,this is not always effective and is often impracticable4 ,table #a gives the sizes of fire-clay flue linings ordinarily provided for boilers1 furnaces1 stoves1 or convection heaters burning soft coal4 ,these sizes have proved satisfactory for average flat-grate furnaces under normal conditions4 ,manufacturers of heating equipment usually specify certain requirements in chimney construction and will not guarantee the performance of their heaters unless these requirements are met4 ,therefore their recommendations should be followed when differing materially from the dimensions given in this bulletin4 ,height of ,chimney ,a chimney should extend at least #c feet above flat roofs and #b feet above the ridge of peak roofs4 ,where chimneys cannot be built high enough above the ridge to prevent trouble from eddies caused by wind being deflected from the roof1 a hood may be provided with the open ends parallel to the ridge4 ,eddies which force air down the flues may be caused by building the chimney too near trees 7fig4 #e1 ,b7 or a higher structure 7fig4 #f74 #a ,farmers' ,bulletin #afih1 ,heating the ,farm ,home1 contains information on estimating the size of the heating plant needed for houses of different sizes and for determining grate areas4 ,illustration3 ,figure #b4--;,heavy masonry chimneys of this type are still being built in rural areas4 ,the thick walls1 with unlined flues1 are in good condition after #ge years of continuous use4 ,table #a4--,sizes of flue linings and heights of chimneys recommended for flat-grate furnaces burning soft coal,a ,nominal size of flue lining ---------------------------------------- ----------- ,height of ,grate ,round 7inside chimney top area diameter7 ,rectangular 7outside above grate 7,sq4 at elevation dimensions7 at elevation at elevation ft47 indicated indicated indicated - ---------------- -------------------------------------- -------------- ,,sl #b,k #d,k #f,k ,sea ,level #b1jjj ft #d1jjj ft #f1jjj ft ,,sl #b,k #d,k #f,k - ---------------- -------------------------------------- -------------- ,in ,in ,in ,in ,in ,in ,in ,in ,ft ,ft ,ft ,ft #a #h #h #h #aj #h by #h #h by #h #h by #h #h by #ac #bb #bf #cb #cf #b #aj #aj #aj #aj #h by #ac #h by #ac #h by #ac #h by #ac #bd #bi #ce #da #c #aj #aj #ab #ab #h by #ac #h by #ac #ac by #ac #ac by #ac #bf #cc #da #di #d #ab #ab #ab #ab #ac by #ac #ac by #ac #ac by #ac #ac by #ac #cj #cg #de #di #e #ab #ab #ae #ae #ac by #ac #ac by #ac #ac by #ah #ah by #ah #cb #cg #dc #eb #f #ae #ah #ah #ah #ah by #ah #ah by #ah #bj by #bj #bj by #bj #cj #cg #dg #ef #g #ah #ah #ah #ah #bj by #bj #bj by #bj #bj by #bj #bj by #bj #cb #da #di #fd #h #ah #ah #ah #ah #bj by #bj #bj by #bj #bj by #bj #bj by #bj #ce #db #ef #aj ,a ,if anthracite is to be burned the area of the flue cross section may be reduced about #be percent4 ,the ratings given are based on comparatively smooth lined flues with no offsets greater than #cj with the vertical4 ,the smallest sizes of fuels require excessive drafts and may necessitate taller chimneys4 ,flue heights and sizes are based upon approximately the several altitudes indicated2 it is sufficiently accurate to use the column giving the altitude nearest to that of the particular problem4 ,when #b or #c appliances are connected to the same flue their total grate area may be reduced #ae percent4 ,the method of determining the proper flue size for an altitude of #b1jjj feet1 when #a appliance with a grate area of #c square feet and another with an area of #a4e square feet are attached to the same flue1 is shown by the following example3 ,add the #b grate areas1 #c #a4e #d4e square feet4 ,reduce this total area by #ae percent4 ,thus1 #d4e - #j4fh #c4h square feet is the required area4 ,use the nearest whole number1 #d4 ,from the table it is seen that for a grate area of #d square feet at an elevation of #b1jjj feet either a #ab-;inch 7inside diameter7 round flue or a #ac- by #ac-;inch 7outside dimensions7 rectangular flue #cg feet high is required4 ,illustration3 ,figure #c4--,this tall chimney produced good draft for the kitchen range1 but the flue was too small for a furnace4 ,when the house was remodeled1 its appearance was greatly improved by building the chimney inside4 ,illustration3 ,figure #d4--,short chimneys are frequently provided for low bungalows1 for architectural reasons4 ,this flue is ample in size but not high enough for use with a stove4 ,the stone masonry has been laid to harmonize with the rustic surroundings4 ,frequently metal-pipe extensions are provided to increase the height of a flue on account of the low cost and ease of installation1 but these must be securely anchored against wind and have the same area as the flue4 ,metal extensions are likely to rust in a short time4 ,they are available with a metal cowl or top that turns with the wind to prevent air blowing down the flue4 ,terra-cotta chimney pots or extensions are more durable and attractive4 ,a chimney located entirely inside a building has better draft because the masonry retains heat longer when protected from cold outside air4 ,illustration3 ,figure #e4--,two pleasingly designed fireplace chimneys that fit into their surroundings4 ,a1 ,this chimney stands in the clear and should provide a good draft2 ,b1 a chimney under overhanging trees is likely to backdraft4 ,contrast the appearance of these two chimneys with that of figure #c4 ,illustration3 ,figure #f4--,several extensions were necessary before this chimney would draw properly on account of the wind deflected from the nearby wall4 ,illustration3 ,figure #g4--;,a1 ,a good foundation extending below the soil affected by frost4 ,this chimney is well protected from ground moisture by the concrete carried above the surface2 ,b1 an insecure foundation4 ,supporting a chimney in this manner is a dangerous practice4 ,,construction ,supporting the ,chimney ,stable foundations1 preferably of concrete1 should be provided1 at least #f inches wider all around than the chimney and #h inches thick for one-story and #ab inches thick for two-story houses4 ,when there is no basement or cellar 7fig4 #g1 ,a71 start the foundation of an exterior chimney well below the frost line2 otherwise1 extend the base to the same level as the bottom of the foundation of the building4 ,foundations for tall1 heavy chimneys require special consideration4 ,where the wall of the house is of solid masonry #ab inches or more thick1 the chimney may be offset and carried on corbels or masonry brackets instead of being carried down to the ground4 ,the offset should not extend more than #h inches from the face of the wall1 each course projecting not more than #a inch1 and should not be less than #ab inches high4 ,often the corbeling is started at the second- or third-floor level so that the chimney is only one or two stories high4 ,illustration3 ,figure #h4--;,for structural safety the amount of offset must be limited so that the center line1 ,,xy1 of the upper flue will not fall beyond the center of the wall of the lower flue4 ,a1 ,offsetting of the left wall of an unlined flue is started two brick courses higher than on the right wall so that the area of the sloping section will not be reduced after plastering2 ,b1 a lined flue showing the method of cutting the tile4 ,chimneys in frame buildings should be built from the ground up or should rest on the foundation or basement walls if of solid masonry #ab inches or more thick4 ,a chimney resting on or carried by wooden floors1 beams1 or brackets or hung from wooden rafters 7fig4 #g1 ,b7 is a fire hazard4 ,wood framing shrinks1 and beams supporting heavy loads deflect in time4 ,sagging beams injure the walls and ceilings of the house and are apt to crack the chimney1 rendering it dangerous4 ,flue ,linings ,although1 to save expense1 chimneys are built without flue lining1 those with linings are more efficient4 ,when the flue is not lined1 the mortar and bricks directly exposed to the action of fuel gases disintegrate4 ,this disintegration and that occurring from changes in temperature frequently cause cracks in the masonry1 thereby reducing the draft4 ,an unlined chimney is best if not plastered except at the sloped section 7fig4 #h1 ,a74 ,however1 the vertical and horizontal joints should be filled with mortar and struck smooth and flush with the wall4 ,offsets or bends in flues 7fig4 #h7 should not be greater than #cj with the vertical4 ,this slope can be obtained by offsetting or corbeling each brick course only #a inch4 ,flue lining must withstand rapid fluctuations in temperature and be resistant to the action of ordinary flue gases4 ,the shapes used as flue lining should be of fire-clay1 with shells not less than five-eighths of an inch thick1 and should be vitrified4 ,as a safeguard against over-burning and brittleness1 the lining should be tested by submersion in water at room temperature for #bd hours1 during which a quantity of water weighing more than #c percent of the dry weight of the lining should not be absorbed4 ,place each length of flue lining in position1 setting it in cement mortar with the joint struck smooth on the inside1 and then lay the brick around it4 ,if the lining is slipped down after several courses of brick have been laid1 the joints cannot be filled and leakage is almost sure to result4 ,fill any spaces between the lining and the brickwork completely with mortar1 especially if the round type of flue is used4 ,the lower section of flue lining1 unless resting on solid masonry at the bottom of the flue1 should be supported on at least three sides by brick courses projecting to the inside surface of the lining4 ,when laying brick and lining1 it is advisable to draw up a tight-fitting bag of straw as the work progresses so as to catch material that might fall and block the flue4 ,where offsets or bends are necessary in lined flues1 tight joints can be made by mitering or cutting equally the ends of abutting sections 7fig4 #h1 ,b74 ,this can be done if a cement sack of damp sand is stuffed firmly into the lining and a sharp chisel is tapped with a light hammer along the line where the cut is desired4 ,if the cutting is done after the lining is built into the chimney1 the lining may be broken and fall out of place4 ,the hole for the thimble can be cut the same way when a special thimble section is not used4 ,the linings commonly used are rectangular or round4 ,rectangular linings are better adapted to brick construction than round linings1 but the latter are considered more efficient4 ,the sizes commonly used are indicated in table #b4 ,wall ,thickness ,walls of chimneys not more than #cj feet high when lined should be #d inches thick if of brick and reinforced concrete1 #h inches if of hollow building units1 and #ab inches if of stone4 ,linings may be omitted in chimneys having walls of reinforced concrete at least #f inches thick or of unreinforced concrete or brick at least #h inches thick1 although lining is desirable in the case of brick construction4 ,also the outside wall of a chimney exposed to the weather is best made at least #h inches thick4 ,in chimneys containing three or more flues1 building codes generally require that each group of two flues be separated from the other single flue or group of two flues by brick divisions or withes not less than #c inches wide 7fig4 #i7 4 ,where two flues are grouped without divisions1 joints in the linings of adjacent flues are safer if staggered at least #g inches1 and particular care should be taken to have all joints filled with mortar4 ,individual flues are advisable for fireplaces and heating furnaces or boilers4 ,table #b4--;,dimensions of commonly used standard commercial flue lining ,rectangular linings,b ,outside ,cross-sectional area ,wall dimensions --------------------- thickness 7inches7 ,inside ,outside ----------- ---------- -------- ---------- ,square ,square inches feet ,inches #d by #h #bc4f #j4bf #e_/h #d by #ac #ch4b 4#da #e_/h #g by #g #ci4a 4#ci #e_/h #h by #h #eb4f 4#ej #e_/h #h by #ac #hj4e 4#gh #c_/d #h by #ah #aji4g #a4aj #g_/h #ac by #ac #abf4f #a4bj #g_/h #ac by #ah #ahb4h #a4gj #g_/h #ah by #ah #bdh4a #b4cj #a-a_/h #bj by #bj #big4f #b4fj #a-c_/h ,round linings,c ,inside ,cross-sectional area ,wall diameter --------------------- thickness 7inches7 ,inside ,outside ----------- ---------- -------- ---------- ,square ,square inches feet ,inches #f #bh4c #j4bi #e_/h #h #ej4c 4#di #c_/d #aj #gh4e 4#ge #g_/h #ab #aac4j #a4jg #a #ae #agf4g #a4fb #a-a_/h #ah #bed4d #b4bi #a-a_/d #bj #cad4a #b4hb #a-c_/h #bb #chj4a #c4dh #a-e_/h #bd #deb4c #d4je #a-e_/h #bg #egb4e #e4bj #b ,b ,all rectangular flue lining is #b feet long4 ,c ,round flue lining1 #f to #bd inches in diameter1 is #b feet long2 that #bg to #cf inches in diameter is #b or #c feet long4 ,illustration3 ,figure #i4--;,cross section of chimney showing the proper arrangement for three flues4 ,the division wall should be well bonded with the side walls by staggering the joints of successive courses4 ,note the studs are kept #b inches away from the brickwork for reasons explained on page #ad4 ,when two or more flues are used in unlined chimneys1 they must be separated by well-bonded withes #h niches thick4 ,an attractive and effective method of separating unlined flues in colonial times is shown in figure #aj4 ,chimneys extending above the roof are exposed to the wind and may sway enough during a gale to open up the mortar joints at the roof line4 ,openings in a flue at this point are especially dangerous because sparks from the flue may come in contact with the woodwork of the roof4 ,it is therefore good practice to make the upper walls #h inches thick 7fig4 #aa7 by starting to offset the bricks just below the intersection with the roof4 ,the brickwork around all fireplaces and flues should be laid with cement mortar1 as it is more resistant than lime mortar to the action of heat and flue gases4 ,a good mortar to use in setting flue linings and all chimney masonry1 except firebrick1 consists of #a part portland cement1 #a part hydrated lime1 and #f parts clean sand1 measured by volume4 ,slacked-lime putty may be used in place of hydrated lime2 firebrick is best laid in fire-clay4 ,illustration3 ,figure #aj4--,this ,williamsburg chimney shows the pains taken to make the chimney attractive4 ,the three flues are arranged as a ,t with well-bonded withes between them4 ,often four flues were used in the form of a cross4 ,openings ,into the ,chimney ,no range1 stove1 fireplace1 or ventilating register should be connected with the flue being used for the heating apparatus because this is a frequent cause of unsatisfactory operation4 ,fires may occur from sparks passing into one flue opening and out through another where there are two connections to the same flue4 ,if an abandoned fireplace chimney is to be used for a range or stove1 close the fireplace flue tight about a foot below the smoke pipe hole4 ,illustration3 ,figure #aa4--;,greater resistance to the weather is provided by building the exposed upper section of a chimney with #h-;inch walls4 ,also the mortar joint1 in which the counter-flashing is embedded1 is not so likely to fail as it is when the wall is only #d inches thick4 ,gas-fired house heaters and built-in unit heaters1 if not connected to a masonry chimney1 may be connected to flues of corrosion-resistant sheet metal not lighter than #bj-;gage1 properly insulated with asbestos or other fireproofing material that will comply with the recommendations of the ,underwriter's ,laboratories1 ,inc4 ,such flues should extend through the roof4 ,a soot pocket#b is desirable for each flue4 ,deep pockets permit the accumulation of soot1 which may take fire2 therefore start them from a point preferably not more than #h inches below the center line of the smoke pipe intake and fill the lower part of the chimney with solid masonry instead of extending the pocket to the base of the chimney as is often done4 ,clean-out doors are necessary at the bottom of deep pockets and1 if used1 must fit snugly and be kept tightly closed so that air cannot get in4 ,clean-outs should serve only one flue1 for if two or more flues are connected with the same clean-out1 air drawn from one to another affects the draft in all of them4 ,sometimes a door is placed just below the smoke pipe1 but one is not really necessary since the pipe1 if taken down each year for cleaning1 allows removal of soot from shallow pockets through the pipe hole4 #b ,see soot pockets and clean-out doors in figures #ab and #ce1 pp4 #ac and #ch1 respectively4 ,close pipe holes1 when temporarily not in use1 with tight-fitting metal flue stops2 but1 if a pipe hole is to be abandoned1 fill it with bricks laid in good mortar4 ,this stopping can be readily removed4 ,the practice of closing a pipe hole with papered tin is dangerous1 for if there is another stove connected with the flue1 the metal may become hot enough to scorch the unprotected wallpaper or even set it afire4 ,proper care in setting and looking after pipe at its connection with the chimney will greatly lessen the number of fires chargeable to defective construction4 ,fit the pipe so that no opening will be left around it1 and keep it from projecting into the flue4 ,the connection can be made airtight with a closely fitting collar and boiler putty1 good cement mortar1 or stiff clay4 ,smoke pipes should enter the chimney horizontally1 and the hole through the chimney wall to the flue should be lined with fire-clay1 or metal thimbles should be securely and tightly built in the masonry4 ,thimbles or flue rings can be had of #f-1 #g-1 #h-1 #aj-1 and #ab-;inch diameters and #f-1 #i-1 and #ab-;inch lengths4 ,if the walls are furred 7fig4 #ab71 the space between the thimbles and the wood furring should be covered with metal lath and plaster4 ,illustration3 ,figure #ab4--;,a1 ,connection to chimney where furring is used4 ,the brick are built out around the thimble as a protection against its cracking4 ,this is a fire hazard that is frequently overlooked4 ,b1 ,connection when plaster is applied directly to the masonry4 ,note that the pipe extends too far into the flue4 ,it should be as shown in ,a4 ,when a smoke pipe is less than #ah inches from woodwork1 the woodwork requires protection against charring4 ,a metal casing or asbestos board #b inches from the upper half of the pipe is sometimes employed to protect woodwork directly above it4 ,a pipe1 even so protected1 should never be closer than #i inches to any woodwork or other combustible material4 ,commercial fireproof pipe coverings can be purchased4 ,if a pipe must be carried through a wood partition1 protection for the woodwork can be provided by cutting an opening in the partition and inserting a galvanized-iron double-wall ventilating shield at least #ab inches larger than the pipe 7fig4 #ac7 or by using at least #d inches of brickwork or other incombustible material4 ,smoke pipes should never pass through floors1 closets1 or concealed spaces or enter a chimney in a garret4 ,gases formed by burning the sulfur contained in coal are the main cause of corrosion of metal smoke pipes4 ,little corrosion occurs during the heating season1 when the pipe is kept hot and dry4 ,the life of metal pipes can be prolonged if each summer when they are not in use they are taken down1 cleaned1 wrapped in paper1 and stored in a dry place4 ,this is especially true of pipe to heaters in damp cellars4 ,illustration3 ,figure #ac4--;,a1 ,elevation of protection around a stovepipe passing through a frame partition2 ,b1 sectional view4 ,illustration3 ,figure #ad4--,method of insulating wood floor joists and baseboard at a chimney with #d-;inch walls4 ,a single header is used as it is less than #d feet long4 ,insulation ,no wood should be in contact with a chimney4 ,leave a space of #b inches between the outside face of a chimney and all wooden beams or joists except when #h inches of masonry is used outside flue lining1 in which case the framing may be within one-half inch of the chimney masonry4 ,the space between the floor framing and the chimney may be filled with porous1 nonmetallic1 incombustible material1 such as loose cinders4 ,brickwork1 mortar1 and concrete are not suitable4 ,place the filling before the floor is laid1 as it not only forms a fire stop but prevents accumulation of shavings or other combustible material4 ,subflooring may be laid within one-half inch of the masonry4 ,baseboards1 when fastened to plaster that is directly in contact with the wall of a chimney1 can be protected by a layer of fireproof material1 such as asbestos1 at least one-eighth of an inch thick between the woodwork and the plaster 7fig4 #ad74 ,wooden studding1 furring1 or lathing should not be placed against a chimney but set back1 as indicated in figure #i2 or the plaster may be applied directly to the masonry or to metal lath laid over the masonry4 ,the former is the better method1 as settlement will not crack the plaster4 ,it is recommended that a coat of cement plaster be applied directly upon the outside surfaces of masonry chimneys that are to be incased by a wooden partition or other combustible construction4 ,metal lath1 lapped #f inches on the masonry1 at the intersection of chimneys with partitions prevents corner cracks4 7,see plan in fig4 #cd47 ,chimney and ,roof ,connection ,where the chimney passes through the roof1 provide a #b-;inch clearance between the wood framing and masonry for fire protection and for expansion due to temperature changes1 settlement1 or slight movement of the chimney during heavy winds4 ,illustration3 ,figure #ae4--,method of flashing4 ,sheet metal1 h1 over the cricket1 extends under the shingles k1 at least #d inches and is counter-flashed at l in joint4 ,base flashings b1 c1 d1 and e and cap flashings a1 f1 and g lap over the base flashings and provide watertight construction4 ,a full bed of mortar should be provided where cap flashing is inserted in joints4 ,a chimney must be flashed and counter-flashed 7fig4 #ae71c to make its junction with the roof watertight4 ,when the chimney is not located on the ridge but on a sloping roof1 a cricket1 j1 is built1 as detailed in figure #af1 high enough to shed water around the chimney4 ,corrosion-resistant metal1 such as copper1 galvanized metal1 zinc1 or lead1 is best for the flashing and counter-flashing4 ,when tin is used1 paint it well on both sides4 #c ,see p4 #bf1 ,farmers' ,bulletin #agea1 ,roof ,coverings for ,farm ,buildings and ,their ,repair1 for method of installing flashing4 ,a feature1 said to have originated in colonial ,williamsburg as a precaution against fire hazard1 is to build the upper section of outside chimneys #ah inches to #b feet away from the gable ends of the house 7fig4 #ag74 ,this is not only a safety factor but a practical one because the chimney can be more easily flashed1 small windows can be used in the walls of upper story rooms behind the chimney1 and framing the roof is simplified4 ,capping the ,chimney ,various methods of terminating chimneys are shown in figures #aa and #ah4 ,whatever one is used should be architecturally acceptable1 effective in preventing disintegration1 and so made as to keep water out of the flue4 ,illustration3 ,figure #af4--;,cricket1 j1 as seen from the back of the chimney shown in figure #ae4 ,a section through the cricket is also shown4 ,note how counter-flashing is built into the mortar joint at l4 ,it is advisable to project the flue lining #d inches above the cap or top course of brick and surround it with at least #b inches of cement mortar finished with a straight or concave slope to direct air currents upward at the top of the flue2 the sloped mortar also serves to drain water from the top of the chimney4 7,see fig4 #aa47 ,hoods are commonly used to keep rain out of a chimney 7fig4 #ah1 ,a and ,b74 ,the area of the hood openings should be at least equal to the area of the flue and each flue should have a separate hood4 ,concrete and brick caps are usually made #d inches thick1 and it is advisable to project them an inch or two to form a drip ledge4 ,many of the chimneys built today are unsightly and frequently detract from an otherwise well-designed house4 ,within the last #ajj years the size and attractiveness of chimneys ordinarily built has declined4 ,the large old chimneys of colonial days were proportioned to suit the house and surroundings and at the same time provide for two or more large fireplaces4 ,with reduction in the size of fireplaces and the substitution of several stoves and eventually one central heating plant1 the chimney has developed into a merely utilitarian shaft4 ,illustration3 ,figure #ag4--;,a house in southern ,maryland in which the space between the chimney and the house wall shows clearly4 ,the practice of building the chimney in this way is common in the tidewater section of the ,south4 ,spark ,arresters ,spark arresters are desirable and1 where chimneys are near combustible roofs1 lumber1 forests1 etc41 they are sometimes required1 depending on the kind of fuel1 waste materials1 or refuse that may be burned and the amount of deposits that may accumulate in the flues4 ,while arresters cannot be depended on to eliminate entirely the discharge of sparks under all conditions2 yet1 when properly built and installed1 they materially reduce spark hazard4#d #d ,see ,standards for ,construction and ,installation of ,spark ,arresters for ,chimneys and ,stacks1 published by the ,national ,fire ,protection ,association4 ,in general all parts1 whether of wire1 expanded metal1 or perforated sheets1 give longer service if they are of rust-resistant material4 ,arresters for domestic purposes should have vertical sides extending upward not less than #i inches so as to provide a gross area of surface at least twice the net flue area4 ,they should be kept outside of the flue area and be securely anchored to the chimney top4 ,openings in the screen not larger than five-eights of an inch nor smaller than five-sixteenths of an inch are advisable4 ,commercially made screens can be purchased which generally last several years4 ,arresters must be kept adjusted in position and renewed when the openings are worn larger than the normal screen openings4 ,illustration3 ,figure #ah4--;,a1 ,a common type of arched hood2 ,b1 flat stone hood2 note the withe separating the two flues4 ,,estimating ,,brick ,the number of standard-size brick 7#h by #c by #b inches7 required to build a straight chimney having only two or three flues can be estimated by drawing the flue lining to scale and then drawing lines #d inches to #h inches outside of the lining depending on the thickness of the brick walls4 ,lay out #d- by #h-;inch rectangles in the space between the lining and the outside lines to determine how many brick are needed per course4 ,for example1 #ae brick are needed for each course of the chimney in figure #i4 ,assuming the height is #cj feet and one-half-inch mortar joints are used1 also that there are #d courses per foot1 there would be #ace courses4 ,therefore1 #ace multiplied by #ae equals #b1jib brick2 about #ajj more will be needed to make the lower portion solid1 or #b1bjj brick in all4 ,a more general method of estimating that is applicable to more complex structures is given on page #dc4 ,methods of determining the quantity of mortar materials1 labor1 and cost are also given and can be applied to this example4 ,,smoke ,,test ,every flue should be subjected to the following smoke test before the heater is connected with it and preferably before the chimney has been furred and plastered or otherwise enclosed4 ,build a paper1 straw1 wood1 or tar-paper fire at the base of the flue4 ,when the smoke is rising in a dense column1 tightly block the outlet at the top of the chimney with a wet blanket4 ,smoke that escapes through the masonry indicates the location of leaks4 ,frequently this test reveals bad leaks into adjoining flues or directly through the walls or between the linings and the wall4 ,remedy defects before the chimney is accepted for use4 ,such defects are usually difficult to correct2 hence it is wise to watch the construction closely as it progresses4 ,,cleaning ,,and ,,repairing ,,flues ,chimneys develop defects which if not promptly repaired cause trouble4 ,most masonry requires replacement of worn or weathered material or repointing of mortar joints1 while flues become clogged and flashings fail4 ,it is advisable to test a chimney every few years for tightness by the smoke test just described2 to examine the inside of the flues by lowering a lantern or flashlight on a strong cord down from the top of the chimney or by holding a hand mirror at the proper angle at a stovepipe hole2 to inspect the masonry for loose units1 which are most likely to occur at the top 7fig4 #c7 where the action of the flue gases1 especially when soft coal is burned1 disintegrates the mortar2 to test mortar joints from the outside by prodding with a knife or similar tool to determine if the mortar is loose clear through the joint so as to leave a hole2 and to notice if the chimney is damp because of leaky flashings1 absorption of moisture from the ground1 condensation1 or excessive rain entering the flues4 ,cleaning ,bricks that fall from the top and lodge at offsets or contracted sections can sometimes be reached and dislodged by a long pole or sections of pipe screwed together4 ,they can be caught on a shingle or piece of sheet metal shoved into a stovepipe hole or removed through a clean-out door4 ,a weighted cement sack filled with straw and attached to the end of a rope may be pulled up and down the flue to remove soot and loose material if the offset is not too great4 ,trouble with creosote and soot can be reduced when one understands how they are formed4 ,smoke and soot are caused by imperfect combustion1 usually due to one or all of the following conditions3 7#a7 ,lack of sufficient air to the fire2 7#b7 improper mixture of air with furnace gases2 7#c7 low furnace temperature2 7#d7 too small combustion space so that the gases reach the comparatively cool furnace surface before they are completely burned and1 as a result1 soot or tarry matter condenses and then passes up the chimney in the form of smoke4 ,soft coal causes more soot trouble than hard coal4 ,if soot accumulates fast or trouble is experienced with unusual smoke when firing1 it is probable that the heating equipment is not being operated properly4 ,the manufacturer or installer usually is able to suggest proper adjustments4 ,investigations by the ,united ,states ,bureau of ,mines#e have shown that various materials on being burned or volatilized form a vapor or smoke which settles upon soot2 causing it to ignite at a lower temperature and burn more easily4 ,for soot to burn1 the gases in contact with it must have a temperature high enough to ignite it and sufficient air to support the combustion4 ,the effectiveness of burning varies with the composition of the remover1 but it also depends upon conditions being favorable4 ,it will usually reduce somewhat the soot in a furnace and smoke pipe but not in a chimney4 ,it has no effect on the ash mixed with the soot4 ,this ash not only does not burn1 but prevents complete burning of the soot mixed with it4 #e ,nichols1 ,p41 and ,staples1 ,c4 ,w4 ,,removal ,,or ,,soot ,,from ,,furnaces ,,and ,,flues ,,by ,,the ,,use ,,of ,,salts ,,or ,,compounds4 ,u4 ,s4 ,bur4 ,mines ,bul4 #cfj1 #gf pp41 illus4 #aicb4 ,soot removers cause soot to burn and are fire hazards4 ,the correct and most thorough method of cleaning a chimney is to do so manually or to employ modern exhaust or vacuum methods used by furnace repairmen4 ,however1 it is inconvenient to remove soot and ash accumulations thoroughly more than once a year2 hence a remover may help to keep the passages of stoves and heaters clear between annual cleanings1 if deposits of soot accumulate quickly and reduce the draft4 ,likelihood of success in cleaning is greater when the deposits of soot are thick1 provided they do not cut down the draft too much4 ,if burning is employed1 there is less risk when it is done frequently enough to prevent large accumulations1 which cause intense fires4 ,also1 freeing the heater and pipe of soot permits better fuel burning and higher temperatures in the chimney flue1 thus reducing the amount of soot likely to be deposited on the flue walls4 ,common salt 7rock or ice-cream salt7 is not the most effective remover1 yet it is the most widely used because of its cheapness1 ease of handling1 and general availability4 ,use two or three teacupfuls per application4 ,metallic zinc in the form of dust or small granules is often used2 however1 a mixture of salt and #aj percent zinc dust is more effective than either salt or zinc alone4 ,one of the most effective mixtures of materials readily available is #a part dry red lead and #e parts common salt1 measured by weight4 ,shake these together in a can with a tight-fitting lid4 ,as lead is poisonous1 wash the hands after using4 ,one or two teacupfuls are used per application4 ,old dry-cell batteries contain suitable ingredients and when they are thrown in a hot furnace the soot usually burns4 ,quicker action can be had if they are chopped up4 ,before a remover is used1 the fire must be put in good condition with a substantial body of hot fuel on top4 ,close the ash-pit door and the slots in the firing door and scatter the remover on the hot coals4 ,close the firing doors and at once reduce the draft by partially closing the pipe dampers4 ,the draft should not be closed so tight as to cause fumes to escape into the cellar4 ,let the remover stew for #aj to #bj minutes or until fumes stop rising from the coals2 then make the fire burn fiercely by opening the ash-pit door and the damper4 ,shaking ashes out will help4 ,the slots in the firing door can be opened or the door itself set ajar4 ,if soot in the furnace will not ignite1 throw a little wood or paper on the fire4 ,instead of making a special job of cleaning at intervals1 one or two cups of salt may be thrown on the fire once a day with the expectation that the furnace will produce a high enough temperature to ignite some of the soot4 ,this is most likely to succeed in cold weather when the furnace temperatures are high4 ,cause of ,creosote ,creosote is the result of condensation in the chimney1 and trouble from this source is best avoided by preventing creosote formation4 ,it is more likely to form when wood is used for fuel than when coal is burned and is more likely to form in cold than in mild climates4 ,green wood may contain as high as #dj percent water1 and dry wood #ae to #bj percent4 ,when wood is slowly burned1 it gives off acetic and pyroligneous acid1 which in combination with water or moisture form creosote4 ,when the draft is strong and an active fire is maintained1 much of the creosote is carried off into the atmosphere4 ,the trouble is aggravated when the fire does not burn briskly and when an outside flue is subjected to chilling blasts4 ,the walls of the chimney1 being comparatively cool1 cause condensation of the vapors contained in the smoke4 ,thus the creosote condenses and runs down the flue1 finding its way out of any joints that are not perfectly tight4 ,the formation of creosote is unusual in chimneys that are surrounded by warm rooms4 ,the outer walls of a chimney in an outside wall should be at least two bricks thick and the chimney should have a good flue lining4 ,creosote is difficult to remove and when it ignites makes a very hot fire that is likely to crack the masonry and char adjacent timbers4 ,the only safe method of removal is to chip it from the masonry with a blade or straightened-out hoe attached to a pipe or handle4 ,a heavy chain drawn up and down the flue walls is sometimes effective4 ,however1 when creosote is removed1 care is necessary not to knock out mortar joints or to break the flue lining4 ,large quantities of salt thrown on the fire in the grate or fireplace will extinguish a chimney fire4 ,a fire in a fireplace flue can be checked in its intensity and frequently extinguished by first quenching the fire on the hearth and then holding a wet rug or blanket over the opening so as to shut off the air4 ,when this is done1 the soot and creosote are likely to slide from the flue walls and drop into the fireplace4 ,before extinguishing a fire in a flue1 cover openings into the rooms1 so that the soot will not spread over furnishings4 ,repairing ,chimneys ,when a chimney is damp1 examine the flashing at the junction with the roof1 especially if wet spots appear on the ceilings of rooms4 ,methods of repairing flashing are given in ,farmers' ,bulletin #agea1 ,roof ,coverings for ,farm ,buildings and ,their ,repair4 ,if the flashing is sound1 possibly water runs down the inside of the flue and through defective mortar joints4 ,where these cannot be reached readily1 the chimney may have to be torn down and rebuilt4 ,sometimes a hood 7fig4 #ah1 ,a and ,b7 is built on top of the chimney to keep out water or to prevent wind blowing down it4 ,to prevent dampness being drawn up from the ground1 the mortar can be raked from a joint at least #ab inches above the ground and a layer of slate1 asbestos shingles1 or rust-resistant sheet metal and new mortar worked into the joint4 ,this work should be done by a mason4 ,if bricks are porous or eroded1 raking out the mortar one-half of an inch deep and applying three-fourths of an inch of cement plaster to the surfaces is effective4 ,eroded joints in the rest of the masonry should be raked and repointed4 ,where natural gas is burned1 dampness due to condensation is not unusual and a drain may be needed4 ,where such conditions exist1 advice should be sought from the manufacturers of the equipment as to the proper remedy4 ,a chimney that becomes too hot to permit holding the hand against it should be carefully inspected by a reliable mason and adequately protected as suggested in the preceding pages4 ,if1 after a chimney is cleaned1 an examination discloses holes1 unfilled joints1 or other unsound conditions out of reach for repair1 it is advisable to tear the masonry down and rebuild properly4 ,inside bricks that are impregnated with creosote and soot should not be used in the new work because they will stain plaster whenever dampness occurs4 ,it is almost impossible to remove creosote and soot stains on plaster and wallpaper4 ,sometimes painting the plaster with aluminum-flake paint or waterproof varnish hides the stains4 ,a hatchway cut through a roof is convenient when high chimneys are repaired or cleaned1 especially when access to the roof is difficult4 ,the hatchway should be located so that it will not be necessary to crawl over the roof to reach the chimney and so that a ladder placed on the attic floor will not be too steep for safe ascent4 ,a watertight cover with hooks to prevent its blowing off is essential4 ,such a hatchway is best provided when the building is erected but can be readily built at any time4 ,,fireplaces ,a fireplace is ordinarily considered appropriate to a living room1 dining room1 and bedroom2 however1 basement1 porch1 and outdoor fireplaces are gaining in favor with the householder4 ,also public dining places1 offices1 etc41 frequently have fireplaces for the comfort and for the air of informality they provide4 ,all fireplaces should be built in accordance with the few simple essentials of correct design given herein if satisfactory performance is to be realized4 ,they should be of a size best suited to the room in which they are used from the standpoint of appearance and operation4 ,if too small1 they may function properly but do not throw out sufficient heat4 ,if they are too large1 a fire that would fill the combustion chamber would be entirely too hot for the room and would waste fuel4 ,the location of the chimney determines the location of the fireplace and too often is governed by structural considerations only4 ,a fireplace suggests a fireside group and a reasonable degree of seclusion1 and therefore1 especially in the living room1 it should not be near doors to passageways of the house4 ,,characteristics ,the principal warming effect of a fireplace is produced by the radiant heat from the fire and from the hot back1 sides1 and hearth4 ,in the ordinary fireplace practically no heating effect is produced by convection1 that is1 by air current4 ,air passes through the fire and up the chimney1 carrying with it the heat absorbed from the fire2 at the same time outside air of a lower temperature is drawn into the room4 ,the effect of the cold air thus brought into the room is particularly noticeable farthest from the fire4 ,heat radiation1 like light1 travels in straight lines1 and unless one is within range of such radiation1 little heat is felt4 ,tests made by the ,bureau of ,agricultural ,chemistry and ,engineering showed that about five times the amount of air required for even liberal ventilation may be drawn into a living room by the operation of a fireplace4 ,such excessive ventilation may cause chilling drafts4 ,persons located at advantageous points in the room will be comfortable under such conditions1 but those out of the radiation zone will not4 ,illustration3 ,figure #ai4--;,in #agdd ,franklin promoted a metal fireplace of this type to be set out into a room4 ,these are known as ,franklin stoves and sometimes are equipped with andirons for burning wood or a grate for burning coal4 ,the metal blower1 shown in front of the opening was used with grates and set in place when starting the draft and then removed so that the cheery heat of glowing coals could be enjoyed4 ,at one time this type of stove was highly thought of because it threw out more heat than the built-in fireplace4 ,a few manufacturers specialize in ,franklin stoves because of the present-day demand4 ,tests conducted by this ,bureau indicate that1 as ordinarily constructed1 a fireplace is only about one-third as efficient as a good stove or circulator heater4 ,nevertheless1 they have a place as an auxiliary to the heating plant and for their cheerfulness and charm4 ,in milder climates1 fireplaces may suffice as the sole source of heat2 also certain materials often wasted may be utilized for fuel4 ,the disadvantages of the ordinary fireplace are lessened by modified fireplaces4 ,,modified ,,fireplaces ,the ,franklin stove 7fig4 #ai7 is a type of modified fireplace4 ,the modified fireplaces of today are of several types1 as shown in figures #bj and #ba4 ,both the last two types of modified fireplaces are manufactured as units of heavy metal1 designed to be set into place and concealed by the usual brickwork1 or other construction1 so that no practical change in mantel design is required by their use4 ,the modifications are built-in standard parts of the fireplace--only the grilles show 7fig4 #bb74 ,illustration3 ,figure #bj4--;,in this modified fireplace air enters the inlet1 a1 from outside and is heated as it rises by natural circulation through the back chamber1 c1 and the tubes1 t1 being discharged into the room from the register1 b4 ,air for supporting combustion is drawn into the fire at d and passes between the tubes up the flue ,a damper is also provided to close the air inlet4 ,one advantage claimed for modified fireplace units is that the correctly designed and proportioned firebox1 manufactured with throat1 damper1 smoke shelf1 and chamber1 provides a form for the masonry1 thus reducing the risk of failure and assuring a smokeless fireplace6 ,however1 there is no excuse for using incorrect proportions2 and the desirability of using a foolproof form1 as provided by the modified unit1 merely to obtain good proportions should be considered from the standpoint of cost4 ,even though the unit is well designed1 it will not operate properly if the chimney is inadequate2 therefore the rules for correct chimney construction must be adhered to with the modified unit as well as with the ordinary fireplace4 ,manufacturers claim labor and materials saved tend to offset the purchase price of the unit2 also that the saving in fuel justifies any net increase in first cost4 ,a minimum life of #bj years is claimed for the type and thickness of metal commonly used today in these units4 ,field tests made by this ,bureau have proved that1 when properly installed1 the better designs of modified-fireplace units circulate heat into the cold corners of rooms and will deliver heated air through ducts to adjoining or upper rooms4 ,for example1 heat could be diverted to a bathroom from a living-room fireplace4 ,illustration3 ,figure #ba4--;,in this fireplace the air is not drawn in directly from outdoors but through the inlet1 a1 from the room that is being heated4 ,the air is heated by contact with the metal sides and back of the fireplace1 rises by natural circulation1 and is discharged back into the room from the outlet1 b1 or to another room on the same floor or in the second story4 ,the inlets and outlets are connected to registers which may be located at the front of the fireplace1 as shown in figure #bb4 ,the registers may be located on the ends of the fireplace or on the wall of an adjacent room4 ,the quantity and temperature of the heated air discharged from the grilles in figures #bj and #ba were measured to determine the merits of the convection features4 ,these measurements showed that very appreciable amounts of convected heat are produced by the modified unit when properly installed and operated4 ,discharge-air temperatures in excess of #bjj ,f4 were attained from some of the units tested4 ,the heated air delivered from the discharge grilles of some of the medium-sized units represented a heating effect equivalent to that from nearly #dj square feet of cast-iron radiation of the ordinary hot-water heating system1 or sufficient to heat a #ae- by #ah-;foot room built with average tightness to #gj ,f4 when the outside temperature is #dj ,f4 ,additional convected heat can be produced with some models by the use of forced-circulation fans4 ,illustration3 ,figure #bb4--;,except for the registers and metallic sides and back1 the appearance of modified fireplaces is like that of ordinary ones4 ,an interesting effect is secured by the mirror--the reflection of the opposite wall appears like a recess over the mantel4 ,however1 the nature of operation1 with the unavoidably large quantity of heated air passing up the stack1 makes the inherent over-all efficiency of any fireplace relatively low4 ,therefore1 claims for an increased efficiency of modified fireplaces should be understood merely as constituting an improvement over the ordinary fireplace and not over stoves or central heating plants4 ,when a fireplace is being selected the kind of fuel to be burned should be considered2 also1 the design should harmonize with the room in proportion and detail 7figs4 #bc and #bd74 ,illustration3 ,figure #bc4--;,a well-designed commercial mantel that suits the room4 ,since it is painted the same color as the walls1 it does not focus attention1 as the handsomely carved formal mantel or mahogany shown in figure #cg is intended to do4 ,in colonial days1 when cordwood was plentiful1 fireplaces #g feet wide and #e feet high were common1 especially when used in kitchens for cooking 7fig4 #be74 ,they required large amounts of fuel and too frequently were smoky4 ,where cordwood 7#d feet long7 is cut in half1 a #cj-;inch width is desirable for a fireplace2 but1 where coal is burned1 the opening can be narrower 7fig4 #bf74 ,thirty inches is a practical height for the convenient tending of a fire where the width is less than #f feet2 openings about #cj inches wide 7fig4 #bg7 are generally made with square corners4 ,the higher the opening1 the greater the chance of a smoky fireplace4 ,illustration3 ,figure #bd4--;,another good design is this revival of early ,new ,england architecture1 which is frequently used for remodeling public dining rooms4 ,the random-width pine planks were selected especially for variety in the pattern of the knots4 ,note the use of otherwise wasted space for bookshelves and closet4 ,illustration3 ,figure #be4--;,a1 ,a fireplace at ,mount ,vernon1 ,washington's home1 typical of those used before cooking stoves were introduced4 ,this type of fireplace1 if not too large1 is often retained 7,b7 when a kitchen is remodeled into a living room4 ,note the ,dutch oven at the right1 formerly used for baking4 ,illustration3 ,figure #bf4--;,fireplaces originally intended for wood were frequently bricked up1 and small cast-iron units of this type were built in1 since the large openings required for wood were wasteful when coal was used4 ,this was a very popular type of grate for hotel and private bedrooms about #ahfj and can still be seen in old houses in coal regions4 ,note the plain and neat mantel of wide plank4 ,in general1 the wider the opening the greater should be the depth4 ,a shallow opening throws out relatively more heat than a deep one of the same width but accommodates smaller pieces of wood2 thus it becomes a question of preference between a greater depth which permits the use of large logs that burn longer and a shallower depth 7fig4 #bh1 ,a and ,b7 which takes smaller-sized wood but throws out more heat4 ,in small fireplaces a depth of #ab inches will permit good draft if the throat is constructed as explained above1 but a minimum depth of #af to #ah inches is advised to lessen the danger of brands falling out on the floor4 ,as a rule1 fireplaces on the second floor are smaller than those on the first floor and it is well to follow this practice because the flue height is less for second floor fireplaces 7fig4 #bi74 ,unless a fireplace #f feet wide is fully #bh inches deep1 the logs will have to be split1 and some advantage of the wide opening will be lost4 ,screens of suitable design should be placed in front of all fireplaces 7fig4 #cj74 ,illustration3 ,figure #bg4--,this inexpensive fireplace #cb inches square shows how a plain brick front can be used in a small room4 ,a fireplace #cj to #cf inches wide is generally suitable for a room having #cjj square feet of floor 7fig4 #ca74 ,the width should be increased for larger rooms1 but all other dimensions should be taken from table #c for the width selected4 ,the corner of a room often is the favorite location for a fireplace 7fig4 #cb74 ,fireplaces of the type shown in figure #bh are also built in corners4 ,illustration3 ,figure #bh4--;,a1 ,a shallow fireplace1 with a copper hood1 built as shown in ,b1 throws out considerable heat after the hood gets hot4 ,the wall should be of fire-resistant masonry4 ,illustration3 ,figure #bi4--,this shallow fireplace with a sloping back is a type that was frequently built in bedrooms before the general use of stoves4 ,note the neat and well-proportioned mantel4 ,illustration3 ,figure #cj4--,screens are almost essential to protect the upholstery of nearby furniture from sparks4 ,this fireplace shows artistic use of small stones and makes a pleasing contrast with the log walls4 ,units providing for burning gas are often built in to resemble fireplaces 7fig4 #cc74 ,pleasing designs result from exercising good taste in use of materials and mantels that suit the room4 ,the photographs in this bulletin have been selected to illustrate various architectural effects that can be developed and should help in the choice of a type suitable for houses of different designs4 ,the essentials for safety and utility1 however1 should not be sacrificed for style4 ,illustration3 ,figure #ca4--,this #cf-;inch-wide fireplace does not seem too large for the small room1 but its size would have been accentuated by the use of a mantel4 ,,construction ,the ordinary fireplace is constructed generally as shown in figure #cd4 ,it is essential 7#a7 that the flue have the proper area1 7#b7 that the throat be correctly constructed and have suitable damper1 7#c7 that the chimney be high enough for a good draft1 7#d7 that the shape of the fireplace be such as to direct a maximum amount of radiated heat into the room1 and 7#e7 that a properly constructed smoke chamber be provided4 ,illustration3 ,figure #cb4--;,an adobe fireplace of the ,mexican-,indian type commonly built in the ,southwestern ,states1 especially when the house walls are of adobe4 ,the logs are stood up1 leaning against the back of the grate1 in order to secure a high-licking flame4 ,,dimensions ,table #c gives recommended dimensions for fireplaces of various widths and heights4 ,if a damper is installed1 the width of the opening j1 figure #cd1 will depend on the width of the damper frame1 the size of which is fixed by the width and depth of the fireplace and the slope of the back wall4 ,the width of the throat proper is determined by the opening of the hinged damper cover4 ,the full damper opening should never be less than the flue area4 ,responsible manufacturers of fireplace equipment give valuable assistance in the selection of a suitable damper for a given fireplace4 ,a well-designed and well-installed damper should be regarded as essential in cold climates4 ,when no damper is used1 the throat opening j should be #d inches for fireplaces not exceeding #d feet in height4 ,table #c4--,recommended dimensions for finished fireplaces ,letters at heads of columns refer to figure #cd ,table ,key w ,opening ,width h ,height d ,depth c ,minimum back 7horizontal7 a ,vertical back wall b ,inclined o ,outside dimensions of standard flue lining i ,inside diameter of standard round flue lining w h d c a b o i ---------------------------------------- ----------------- ,inches ,inches ,inches ,inches ,inches ,inches ,inches ,inches #bd #bd #af-ah #ad #ad #af #h by #h #aj #bh #bd #af-ah #ad #ad #af #h by #h #aj #bd #bh #af-ah #ad #ad #bj #h by #h #aj #cj #bh #af-ah #af #ad #bj #h by #ac #aj #cf #bh #af-ah #bb #ad #bj #h by #ac #ab #db #bh #af-ah #bh #ad #bj #h by #ah #ab #cf #cb #ah-bj #bj #ad #bd #h by #ah #ab #db #cb #ah-bj #bf #ad #bd #ac by #aa #ab #dh #cb #ah-bj #cb #aa #bd #ac by #ac #ae #db #cf #ah-bj #bf #aa #bh #ac by #ac #ae #dh #cf #ah-bj #cb #ad #bh #ac by #ah #ae #ed #cf #ah-bj #ch #ad #bh #ac by #ah #ae #fj #cf #ah-bj #dd #ad #bh #ac by #ah #ae #db #dj #bj-bb #bd #ag #bi #ac by #ac #ae #dh #dj #bj-bb #cj #ag #bi #ac by #ah #ae #ed #dj #bj-bb #cf #ag #bi #ac by #ah #ae #fj #dj #bj-bb #db #ag #bi #ah by #ah #ah #ff #dj #bj-bb #dh #ag #bi #ah by #ac #ah #gb #dj #bb-bh #ea #ag #bi #ah by #ah #ah ,illustration3 ,figure #cc4--;,in regions where natural gas is plentiful and in cities1 fireplaces of this type1 burning gas with a flickering flame1 are frequently used as an auxiliary to the main heating plant4 ,some types have imitation logs of metal perforated for gas jets4 ,footings ,footings for chimneys with fireplaces should be provided as described on page #g2 for chimneys without fireplaces1 the footings should rest on good firm soil4 ,illustration3 ,figure #cd4--;,a typical fireplace1 illustrating practical details of construction4 ,an alternate method of supporting the hearth is shown in the lower right-hand corner4 ,the various letters refer to specific features discussed in the text4 ,hearth ,the hearth should be about flush with the floor1 for sweepings may then be brushed into the fireplace4 ,when there is a basement1 an ash dump located in the hearth near the back of the fireplace is convenient4 ,the dump consists of a metal frame about #e by #h inches in size1 with a plate1 generally pivoted1 through which ashes can be dropped into a pit below 7fig4 #ce74 ,illustration3 ,figure #ce4--,the ash-pit should be of tight masonry and should be provided with a tightly fitting iron clean-out door and frame about #aj by #ab inches in size4 ,a clean-out for the furnace flue as shown is sometimes provided4 ,in buildings with wooden floors the hearth in front of the fireplace should be supported by masonry trimmer arches 7fig4 #cd7 or other fire-resistant construction4 ,hearths should project at least #af inches from the chimney breast and should be of brick1 stone1 terra cotta1 or reinforced concrete not less than #d inches thick4 ,the length of the hearth should be not less than the width of the fireplace opening plus #af inches4 ,wooden centering under trimmer arches may be removed after the mortar has set1 though it is more frequently left in place4 ,figure #cf shows a recommended method of floor framing around a fireplace4 ,wall ,thickness ,the walls of fireplaces should never be less than #h inches thick1 and if of stone they should be at least #ab inches thick4 ,when built of stone or hard-burned brick1 the back and sides are often not lined with firebrick1 but it is better to use firebrick laid in fire-clay4 ,when firebricks are laid fiat with the long sides exposed there is less danger of their falling out4 ,they are generally placed on edge1 however1 forming a #b-;inch protection1 in which case metal ties should be built into the main brickwork to hold the #b-;inch firebrick veneer in place4 ,thick metal backs and sides are sometimes used as lining4 ,when a grate for burning coal or coke is built in1 firebrick at least #b inches thick should be added to the fireplace back unless the grate has a solid iron back and is only set in with an air space behind it 7fig4 #cg74 ,jambs ,the jambs should be wide enough to give stability and a pleasing appearance2 they are frequently faced with ornamental brick or tile4 ,for an opening #c feet wide or less1 a #ab- or #af-;inch width is generally sufficient1 depending on whether a wood mantel is used or the jambs are of exposed masonry4 ,the edges of a wood mantel should be kept at least #h inches from the fireplace opening4 ,for wider openings and large rooms1 similar proportions should be kept4 ,illustration3 ,figure #cf4--,where a header is more than #d feet in length1 it should be doubled1 as shown4 ,headers supporting more than four tail beams should have ends supported in metal joist hangers4 ,the framing may be placed one-half inch from the chimney because the masonry is #h inches thick4 ,lintel ,lintels of - by #c-;inch flat iron bars4 #c- by #c- by -inch angle irons1 or damper frames are used to support the masonry over the opening of ordinary fireplaces4 ,heavier lintel irons are required for wider openings4 ,where a masonry arch 7fig4 #ch7 is used over the opening1 the jambs should be heavy enough to resist the thrust of the arch4 ,arches over openings less than #d feet wide seldom sag1 but sagging is not uncommon in wider fireplaces1 especially where massive masonry is used4 ,throat ,the sides of the fireplace should be vertical up to the throat1 or damper opening 7ff fig4 #cd74 ,the throat should be #f to #h inches or more above the bottom of the lintel and have an area not less than that of the flue and a length equal to the width of the fireplace opening4 ,starting #e inches above the throat1 ee1 the sides should be drawn in at tt to equal the flue area4 ,proper throat construction is so necessary to a successful fireplace that the work should be inspected several times a day during construction to make certain that the side walls are carried up perpendicularly until the throat is passed and that the full length of opening is provided4 ,smoke ,shelf and ,chamber ,the smoke shelf is made by setting the brickwork back at the top of the throat to the line of the flue wall for the full length of the throat4 ,its depth may vary from #f to #ab inches or more1 depending on the depth1 d1 of the fireplace4 ,illustration3 ,figure #cg4--;,grates of this type are commonly used in fireplaces for burning coal or coke4 ,this one has a metal back and ends and is only set in to permit proper circulation of air around it4 ,the smoke chamber is the space extending from the top of the throat1 ee1 up to the bottom of the flue proper1 tt #i and between the side walls4 ,the walls should be drawn inward #cj to the vertical after the top of the throat1 ee1 is passed and smoothly plastered with cement mortar not less than one-half inch thick4 ,damper ,a properly designed damper1 as shown in figure #cd1 affords a means of regulating the draft and prevents excessive loss of heat from the room when the fire is out4 ,a damper consists of a cast-iron frame with a lid hinged so that the width of the throat opening may be varied from a closed to a wide-open position4 ,various patterns are on the market1 some designed to support the masonry over the opening1 others requiring lintel irons4 ,illustration3 ,figure #ch4--,this well-designed small stone fireplace was built in accordance with the principles given in this bulletin4 ,it is a good heater and does not smoke4 ,the jambs are wide enough to resist the thrust of the arch4 ,a roaring pine fire may require a full-throat opening1 but slow-burning hardwood logs may need only #a or #b inches of opening4 ,regulating the opening according to the kind of fire prevents waste of heat up the chimney4 ,closing the damper in summer keeps flies1 mosquitoes1 and other insects from entering the house down the chimney4 ,in houses heated by furnaces or other modern systems1 lack of a damper in the fireplace flue may interfere with uniform heating1 particularly in very cold windy weather1 whether or not there is a fire on the hearth4 ,when air heated by the furnace is carried up the chimney there is a waste of the furnace fuel1 but a damper partially open serves a slow fire of hardwood without smoking the room or wasting heated air from the main heating system4 ,illustration3 ,figure #ci4--;,diagram showing front view and cross section of an entire chimney such as is commonly built to serve a furnace1 fireplace1 and kitchen stove4 ,two sets of dimensions are given1 those in rectangles refer to the approximate sizes of the voids or openings2 the others refer to the outside dimensions of the brickwork4 ,these are used in estimating the number of bricks in a chimney4 ,the letters ,a-,f indicate sections used in estimating the quantities of brick required 7,see p4 #dd47 ,flue ,the area of lined flues should be a twelfth or more of the fireplace opening1 provided the chimney is at least #bb feet in height1 measured from the hearth4 ,if the flue is shorter than #bb feet or if it is unlined1 its area should be made a tenth or more of the fireplace opening4 ,the fireplace shown in figure #cd has an opening of #g4e square feet1 or approximately #a1jhj square inches1 and needs a flue area of approximately #ij square inches2 a rectangular flue1 #h by #ah inches1 outside dimensions1 or a round flue with a #ab-;inch inside diameter might be used1 as these are the nearest commercial sizes of lining 7table #b74 ,it is seldom possible to obtain lining having exactly the required area1 but the inside area should never be less than that prescribed above4 ,a #ac- by #ac-;inch flue was selected for convenience when combining with the other flues4 ,if the flue is built of brick and is unlined1 its area should be approximately one-tenth of the fireplace opening1 or #ajh square inches4 ,it would probably be made #h by #af inches 7#abh square inches7 because brickwork can be laid to better advantage when the dimensions of the flue are multiples of #d inches4 ,the principles of construction given under ,chimneys 7p4 #g7 apply to fireplace flues4 ,table #d is convenient in selecting the proper size of flue or for determining the size of fireplace opening for an existing flue4 ,the area of the fireplace opening in square inches is obtained by multiplying the width1 w1 by the height1 h1 7fig4 #cd71 both measured in inches4 ,,cost ,,estimate ,a convenient method for estimating the number of bricks in a chimney is to calculate the volume of the various sections which differ in outside dimensions and then subtract the voids or cavities resulting from ash-pits1 fireplace1 and flues4 ,this will be the total cubic feet of brickwork which1 when multiplied by #bb4e1 is converted to number of bricks4 ,for convenience1 inches as indicated in figure #ci have been converted to decimals of a foot4#f #f ,inches and fractions of an inch are converted to feet and decimals by multiplying by #j4jhcc2 thus #b ,x _/ inches ,o4#jhcc equals #j4bjh feet4 ,table #d4--,sizes of fireplace flue linings,d ,outside dimensions ,inside ,area of of standard diameter of fireplace rectangular standard round opening flue lining flue lining --------- ----------- -------------- ,square inches ,inches ,inches #fjj #h by #h #aj #hjj #h by #ac #aj #a1jjj #h by #ah #ab #a1bjj #h by #ah #ab #a1djj #ac by #ac #ab #a1fjj #ac by #ac #ae #a1hjj #ac by #ah #ae #b1jjj #ac by #ah #ae #b1bjj #ac by #ah #ae #b1djj #ah by #ah #ah #b1fjj #ah by #ah #ah #b1hjj #ah by #ah #ah #c1jjj #ah by #ah #ah ,d ,based on a flue area equal to one-twelfth the fireplace opening4 ,sec table #b for areas of flue lining4 ,number of ,bricks 7#a7 ,estimate the total volume of masonry by multiplying together the length1 width1 and height of the various sections 7fig4 #ci74 ,length ,width ,height ,volume ,section ,feet ,feet ,feet ,cubic feet ,,ab #f4j by #b4ge by #ab4ff #bji4j ,,bc #d4be by #b4e by #a4ff #ag4f ,,cd #c4e by #b4j by #b4j #ad4j ,,de #c4e by #a4ge by #aj4af #fb4b ,,ef #d4cc by #b4e by #f4j #fe4j ------ ,total volume including voids #cfg4 #h 7#b7 ,estimate the total volume of voids by multiplying together their length1 width1 and height4 ,length ,width ,height ,volume ,item ,feet ,feet ,feet ,cubic feet ,ash-pit #b4cc by #a4e by #g4j #bd #df ,fireplace #c4j by #a4e by #c4e #ae4ge ,smoke chamber #b4j by #a4af by #b4j #d4fd #h- by #ac-;inch flue,e #j4gh square feet by #bh #e #bb4bc #ac- by #ac-;inch flue,e #a4bj square feet by #ah4ge #bb4ej #h- by #h-;inch flue,e 4#ej square feet by #ah4ge #i4cg ------ ,total volume of voids #ih4ie ,e ,see table #b for outside areas of flues in square feet4 7#c7 ,subtract volume of voids from volume of masonry4 ,cubic feet ,total volume1 including voids #cfh ,total volume of voids #ii --- ,total volume of masonry #bfi 7#d7 ,multiply net volume of masonry by the number of brick per cubic foot4 #bfi by #bb4e #f1jec brick1 or #f4a thousand bricks4 ,mortar ,to estimate the mortar needed1 multiply the mortar material given below for #a1jjj brick by #f4a to determine how much will be needed to build the chimney1 using #a3a3f mixture recommended on page #aj4 ,bags of hydrated lime #b4f by #f4a #af bags4 ,sacks of portland cement #c4e by #f4a #bb sacks4 ,cubic feet of sand #ah4j by #f4a #aaj cubic feet #d cubic yards4 ,foundation ,concrete needed for foundation can be estimated as follows3 ,concrete for foundation should be #a3b3e and for the top #a3b4 ,the foundation is #g by #c4ge by #a1 or #bf4be cubic feet1 or #a cubic yard1 and will require #e sacks of cement1 #j4df cubic yard of sand1 and #ib cubic yard of gravel4 ,the cap is #d4e by #b4ff by #j4e #e4i cubic feet ,the area of the three flues above must be deducted3 #e4i minus #b4dh #c4db cubic feet1 or one-ninth of a cubic yard4 ,as #a cubic yard was assumed for the foundation1 extra cement and sand are not needed4 ,other material needed3 #a #h-;inch thimble1 #i inches long4 #a #f-;inch thimble1 #i inches long4 #bh feet of #h- by #ac-;inch flue lining4 #bj feet of #ac- by #ac-;inch flue lining4 #bj feet of #h- by #h-;inch flue lining4 ,damper1 #cf- by #aj-;inch throat opening4 #b clean-out doors and #a ash dump4 ,mantel as selected4 ,if firebrick is to be used or the exposed breast is to be of face or special brick 7or ceramic tile7 the number should be counted or estimated and deducted from the number of common brick as estimated above4 ,labor ,the labor required to build a chimney depends on the thickness of the walls1 the height1 and the amount of cutting to build in specialties1 provide offsets1 etc4 ,in general1 a mason will take #af hours with #h hours of laborer's help to lay #a1jjj brick4 ,on this basis1 #af by #f4a #ig4f hours of mason's time and #dh4h hours of laborer's time will be required4 ,cost ,the approximate cost of the chimney can be determined by using actual local cost of materials and wages as follows3,f #f1ajj brick at #ae4jj per thousand #ia4ej #bg sacks of cement,g at #j4gj per sack #ah4ij #af bags of lime at #j4ej per bag #h4jj #e cubic yards of sand,g at #b4be per cubic yard #aa4be #a cubic yard of gravel at #b4jj per cubic yard #b4jj #ih hours1 mason's time1 at #a4jj per hour #ih4jj #di hours1 laborer's time1,h at #j4cj per hour #ad4gj #bh linear feet of #h- by #ac-;inch flue at #a4jj per foot #bh4jj #bj linear feet of #ac- by #ac-;inch flue at #a4ae per foot #bc4jj #bj linear feet of #h- by #h-;inch flue at #j4dj per foot #h4jj #a #h-;inch thimble 4#fj #a #f-;inch thimble 4#dj #b clean-out doors ,damper1 lintel mantel1 ash dump #fe4jj ----- ,total net cost ,i #cfi4ce ,f ,the prices used in this example are merely illustrative4 ,g ,includes material for footing and cap4 ,h ,includes labor for footing and cap4 ,i ,where the chimney is built by contract1 #aj to #ae percent should be added for profit and overhead4 ,,smoky ,,fireplaces ,when a fireplace smokes1 it should be examined to make certain that the essential requirements of construction as outlined in this bulletin have been fulfilled4 ,if the chimney is not stopped up with fallen brick and the mortar joints are not loose1 note whether nearby trees or tall structures cause eddies down the flue4 ,to determine whether the fireplace opening is in correct proportion to the flue area1 hold a piece of sheet metal across the top of the fireplace opening and then gradually lower it1 making the opening smaller until smoke does not come into the room4 ,mark at the lower edge of the metal on the sides of the fireplace4 ,the opening may then be reduced by building in a metal shield or hood across the top so that its lower edge is at the marks made during the test2 or the trouble can generally be remedied by increasing the height of the flue4 ,,outdoor ,,fireplaces ,outdoor fireplaces range from simple makeshifts to elaborately equipped structures harmonizing with the architecture of the house4 ,no one type will meet all conditions1 but all types should be practical to use and yet not be fire hazards or eyesores4 ,illustration3 ,figure #dj4--;,a1 ,a fireplace built for #cj cents1 cash4 ,one hundred and twenty bricks and six concrete blocks were picked up a few at a time along the road4 ,one sack of cement was purchased1 one-half of which was used for another job ,sand was available on the site4 ,b f ,detailed drawings show dimensions of this fireplace4 ,as the fireplace is ordinarily built1 the material would cost about #e and the labor from #e to #aj1 depending on local conditions4 ,,types ,the tendency is to build too large an outdoor fireplace4 ,where only a little cooking is to be done occasionally in a small yard or at a picnic1 several concrete blocks or stones set on the ground about #ab to #af inches apart will serve4 ,the shelf of an old refrigerator may be used for a grille4 ,if permanence is desired1 the walls should be laid in cement mortar and the fireplace should have a suitable foundation and a permanent grille4 ,an end wall is recommended to prevent embers from being scattered by drafts blowing between the side walls4 ,smoke annoyance while cooking is lessened by making the fireplace long enough to permit a short chimney 7fig4 #dj74 ,illustration3 ,figure #da4--;,an outdoor fireplace built back of an inside fireplace and opening onto a paved terrace provides comfort in early fall4 ,a circle of stones laid loosely on the surface1 larger stones set partly into the ground1 or carefully laid masonry walls on a stable foundation may be used for campfires and small barbecue parties4 ,a cast-iron pot with a lid can be buried in the ashes for baking4 ,pipe supports for pots and pans built into the masonry are a convenience2 they can be homemade or purchased4 ,spits for roasting can be improvised or bought4 ,fireplaces opening onto an enclosed porch or paved terrace1 are often built as an integral part of the house chimney 7fig4 #da74 ,the corner of boundary walls permits effective treatment4 ,such fireplaces should meet the regulations of local fire authorities and be built with the same care and be subject to the same rules as inside fireplaces4 ,,obtaining ,,plans ,plans for outdoor fireplaces are available from various publishing houses2 several magazines feature illustrations that can be adapted to the material at hand4 ,if a structure is to be built with local labor and material1 simple designs are advisable4 ,the size of stones1 joints1 and proportions have a direct influence upon appearance1 and good personal taste frequently results in more pleasing structures than blind adherence to conventional designs4 ,the various combinations of ovens1 cranes1 grilles1 storage compartments1 benches1 lights1 sinks1 etc41 to be used as built-in features affect the design4 ,before planning a structure with these features1 catalogs of dealers in outdoor fireplace equipment should be consulted for sizes of the available accessories so that ample space and proper details can be provided in the masonry for building them in4 ,skilled labor should be employed for elaborate designs 7fig4 #db7 when much equipment is built in or when the fireplace1 as in figure #da1 is an integral part of a permanent building4 ,illustration3 ,figure #db4--,this fireplace1 set at a focal point in the garden1 enhances the landscape4 ,it was built by a skilled mason4 ,,construction ,ordinarily the fire is built on the hearth1 no grate being used4 ,fire regulations in hazardous localities may require firing doors1 dampers1 spark screens1 and a solid-plate cooking surface2 otherwise these features are not essential4 ,two and a half square feet of cooking surface is desirable1 while access to both sides and the end permit several people to cook at the same time4 ,the side walls should have fairly level tops for pots and pans4 ,side walls are made #b to #f inches higher than the cooking level to permit anchoring the grille2 if too high1 they interfere with cooking4 ,commercial grilles are available1 but satisfactory ones can be made of -inch to -inch pipe or #e_/h-;inch reinforcing rods4 ,the pipes should be #f to #aj inches longer than the width of the firebox2 they should be spaced not more than #a inches apart and have their tops exactly level to prevent pots and pans from wobbling4 ,two or three pipes can be used for a lintel over the opening into the flue if regular iron lintels are not available4 ,where a solid top is desired1 it should be of boiler plate at least -inch thick4 ,such plates must be stiffened to prevent buckling by alternate heating and cooling2 for ordinary purposes they are merely set on top of the grid though they may be hinged at the rear so they can be tipped back against the chimney4 ,the best draft is secured when the fireplace faces the direction of prevailing breezes and is protected from strong winds which might scatter sparks4 ,if the fireplace is built too near shrubbery or under trees1 the heat and smoke may damage or burn the foliage4 ,a slight rise or a gentle slope that affords good drainage should be selected4 ,paving the ground around the fireplace1 with flagstones or covering it with a layer of gravel or sand will prevent the area from becoming a mudhole or an unsightly bare spot2 also1 danger of starting brush fires by sparks falling from the firebox is lessened4 ,fireboxes #ab to #af inches wide1 #af to #bd inches long1 and #f to #h inches deep with the hearth at #i to #af inches above the ground are sufficient for most purposes4 ,large fireboxes are wasteful of fuel2 while1 if the grille is too high above the hearth1 much of the best cooking heat from glowing coals is lost4 ,most grilles are set #ae to #bd inches above the ground1 though #cj inches may be desirable to avoid the necessity of stooping when cooking4 ,the hearth should slope #a to #b inches toward the front so that rain water will drain away4 ,the area of the chimney flue should be at least one-eighth the vertical cross-sectional area of the firebox4 ,fire-clay linings for the firebox and flue are not absolutely necessary except when required by fire regulations or where hot fires are maintained for long periods4 ,they1 or common brick linings1 are advisable for the more permanent and expensive structures or where it is necessary to use porous stone1 such as sandstone and most stratified rocks1 which absorb water and flake or chip upon exposure to fire4 ,most rocks or stone that can be worked up without special tools or skill1 brick1 and concrete are adaptable for the average fireplace 7fig4 #dc74 ,the size of the stones determines the thickness of the walls2 no wall should be less than #h inches thick4 ,where suitable stone is difficult to get in sufficient quantity1 the exposed surface may consist of a shell the thickness of the stone and the inner portion of the wall be made of concrete or large stone bedded in concrete4 ,when flue lining is necessary1 it will serve as a form for the flue3 otherwise a metal stovepipe makes a practical form1 or the flue can be formed of brick laid on edge4 ,the stones can be laid and the concrete deposited with the least trouble by building the veneer and flue only #f to #h inches high at one time4 ,all masonry should be laid in mortar1 as described on page #aj4 ,concrete made in the proportions #a3b3d will serve most purposes where wall sections are about #h inches thick4 ,for heavy foundations and thick walls not subject to direct fire1 #a3c3f concrete is strong enough4 ,a concrete slab #d to #h inches thick with the bottom #d to #f inches below the surface provides a sufficient foundation for medium-sized structures where frost is negligible and the soil is well drained and firm4 ,if the soil is not well drained a #f- to #h-;inch layer of stone1 cinders1 or sand should be provided under the slab and the surface of the immediate vicinity graded or otherwise protected from water4 ,it is advisable to use -inch or -inch reinforcing rods1 #f inches apart in both directions1 one-third the distance from the top in slabs for all but the smallest fireplaces or where frost is not severe4 ,illustration3 ,figure #dc4--;,a1 ,ground plan of a stone fireplace that can be built in different sizes to suit the landscape2 ,b1 vertical-section sketch2 ,c1 the completed fireplace4 ,the stones for this fireplace were picked up at the swimming hole4 ,about #h bushels were used over a backing of concrete2 #af bushels would have been needed if the concrete had not been used4 ,gravel and sand were dug from the excavation4 ,the chimney is battered #d inches in the #bd-;inch height4 ,heavy and expensive structures1 especially those having tall chimneys1 should have foundations below the surface affected by frost or erosion and strong enough to prevent settlement or cracks4 ,such a foundation can be made of concrete1 with a liberal use of large stones for economy1 extending under the whole structure1 or be continuous walls with a footing similar to those used for houses4 ,the advice and help of builders may save money in the construction of foundations of large expensive fireplaces1 especially where climatic conditions are severe and the bearing power of soil is not known4 ,,operation ,cooking should be done over glowing coals1 as flames and smoke smudge the utensils or even the food4 ,when the wood is nearly charred1 most of the smoke has been driven off and the chimney is hot enough to draw the smoke up the flue4 ,all fires should be banked before they are left1 to avoid setting fires4 ,banking can be safely and effectively done by raking the coals and unconsumed fuel into a pile on the hearth and covering the pile with a few inches of earth4 ,water thrown on a hot fire may result in scalds from the steam and may crack the fireplace4 ,,barbecue ,,pits ,barbecue ovens are rather expensive unless for community use4 ,outdoor fireplaces1 without or with spits for roasting1 are frequently called barbecues in some sections of the country4 ,for occasional barbecuing parties1 a hole in the ground will serve4 ,dig a hole several feet deep and several feet larger each way than the size of the carcass to be roasted2 then place stones in the bottom to retain the heat4 ,a trench #cj inches deep1 #cf inches wide1 and about #aj feet long will accommodate about #djj pounds of beef4 ,a fire should be built sufficiently ahead of time1 about #c hours1 to heat the stones and bottom and accumulate ashes for proper banking4 ,have someone with previous experience operate the pit1 because improper wrapping of the meat and handling of the coals results in poor cooking4 ,,dutch ,,ovens ,dutch ovens 7fig4 #be7 are often built in connection with both indoor and outdoor fireplaces to copy early kitchen fireplaces or for actual baking4 ,when used as an ornament1 the oven is fitted with a cast-iron door1 and the space thus formed may be used for wood storage4 ,an open firebox or compartment below may be similarly used4 ,spaces used for wood storage should be separated from the fireplace by a brick or stone partition at least #h inches thick1 all joints being completely filled with mortar4 ,if the oven is intended for baking1 it is advisable to line it with firebrick1 and the masonry should be at least #h inches thick4 ,a greater heat-storing capacity is secured by using thick walls4 ,an ash drop of standard cast-iron unit type is provided for modern ovens and may lead either to the side of the fireplace or to an ash-pit in the chimney base4 ,the throat or dome should be carefully formed with brick molded or ground to an arch and preferably should be fitted with a damper4 ,if the top of the oven is flat1 several lintel irons will be needed to support the brick4 ,a separate flue with a damper is recommended4 ,for ovens of ordinary size an #h- by #h-;inch flue is ample4 ,the oven is preheated by fire or hot coals4 ,before food is placed in the oven1 the coals and ashes are removed through the ash drop4 ,figure #dd shows a ,dutch oven made of tapered adobe bricks and plastered outside with adobe mud4 ,a hole in the top permits the escape of smoke1 while the oro is being heated by the fire built inside on the floor4 ,this hole is closed with an adobe block after the coals are raked out4 ,when loaves of bread have been placed on the floor with a wooden paddle1 the door hole is stopped with adobe brick4 ,illustration3 ,figure #dd4--,this ,dutch oven of adobe bricks is a type very common in the ,states along the ,mexican border4 ,it is called an oro and is usually built a short distance from the kitchen door4 ,boy ,scouts and campers frequently improvise ,dutch ovens by packing damp sandy clay1 #h to #ab inches thick1 around a wooden barrel1 a tin wash boiler1 or slabs of rock to form a vault4 ,after the earth has been gradually dried and baked with a slow fire1 the oven is ready for use4 ,the hole in the top and the door can be closed as in the oro4 99 99 99 99 99 ,u4 ,s4 ,,government ,,printing ,,office3 #aidg ,for sale by the ,superintendent of ,documents1 ,u4 ,s4 ,government ,printing ,office ,washington #be1 ,d4 ,c4 - ,price #ae cents 99 99 99 99 99 ,transcriber ,note ,the footnotes for the tables were changed from arabic numerals to alphabetic characters to distinguish them from the text footnotes4