Part 4

_Length _Width _Height _Volume _Section_ Feet_ Feet_ Feet_ Cubic feet_ _AB_ 6.0 by 2.75 by 12.66 = 209.0 _BC_ 4.25 by 2.5 by 1.66 = 17.6 _CD_ 3.5 by 2.0 by 2.0 = 14.0 _DE_ 3.5 by 1.75 by 10.16 = 62.2 _EF_ 4.33 by 2.5 by 6.0 = 65.0 ------ Total volume including voids 367. 8

(2) Estimate the total volume of voids by multiplying together their length, width, and height.

_Length _Width _Height _Volume _Item_ Feet_ Feet_ Feet_ Cubic feet_

Ash-pit 2.33 by 1.5 by 7.0 = 24 46 Fireplace 3.0 by 1.5 by 3.5 = 15.75 Smoke chamber 2.0 by 1.16 by 2.0 = 4.64 8½- by 13-inch flue[E] 0.78 square feet by 28 5 = 22.23 13- by 13-inch flue[E] 1.20 square feet by 18.75 = 22.50 8½- by 8½-inch flue[E] .50 square feet by 18.75 = 9.37 ------ Total volume of voids 98.95

[E] See table 2 for outside areas of flues in square feet.

(3) Subtract volume of voids from volume of masonry.

_Cubic feet_ Total volume, including voids 368 Total volume of voids 99 --- Total volume of masonry 269

(4) Multiply net volume of masonry by the number of brick per cubic foot.

269 by 22.5 = 6,053 brick, or 6.1 thousand bricks.

Mortar

To estimate the mortar needed, multiply the mortar material given below for 1,000 brick by 6.1 to determine how much will be needed to build the chimney, using 1:1:6 mixture recommended on page 10.

Bags of hydrated lime 2.6 by 6.1 = 16 bags. Sacks of portland cement 3.5 by 6.1 = 22 sacks. Cubic feet of sand 18.0 by 6.1 = 110 cubic feet = 4 cubic yards.

Foundation

Concrete needed for foundation can be estimated as follows: Concrete for foundation should be 1:2½:5 and for the top 1:2½. The foundation is 7 by 3.75 by 1, or 26.25 cubic feet, or 1 cubic yard, and will require 5 sacks of cement, 0.46 cubic yard of sand, and 92 cubic yard of gravel. The cap is 4.5 by 2.66 by 0.5 = 5.9 cubic feet The area of the three flues above must be deducted: 5.9 minus 2.48 = 3.42 cubic feet, or one-ninth of a cubic yard. As 1 cubic yard was assumed for the foundation, extra cement and sand are not needed. Other material needed:

1 8-inch thimble, 9 inches long. 1 6-inch thimble, 9 inches long. 28 feet of 8½- by 13-inch flue lining. 20 feet of 13- by 13-inch flue lining. 20 feet of 8½- by 8½-inch flue lining. Damper, 36- by 10-inch throat opening. 2 clean-out doors and 1 ash dump. Mantel as selected.

If firebrick is to be used or the exposed breast is to be of face or special brick (or ceramic tile) the number should be counted or estimated and deducted from the number of common brick as estimated above.

Labor

The labor required to build a chimney depends on the thickness of the walls, the height, and the amount of cutting to build in specialties, provide offsets, etc. In general, a mason will take 16 hours with 8 hours of laborer's help to lay 1,000 brick. On this basis, 16 by 6.1 = 97.6 hours of mason's time and 48.8 hours of laborer's time will be required.

Cost

The approximate cost of the chimney can be determined by using actual local cost of materials and wages as follows:[F]

6,100 brick at $15.00 per thousand $91.50 27 sacks of cement[G] at $0.70 per sack 18.90 16 bags of lime at $0.50 per bag 8.00 5 cubic yards of sand[G] at $2.25 per cubic yard 11.25 1 cubic yard of gravel at $2.00 per cubic yard 2.00 98 hours, mason's time, at $1.00 per hour 98.00 49 hours, laborer's time,[H] at $0.30 per hour 14.70 28 linear feet of 8½- by 13-inch flue at $1.00 per foot 28.00 20 linear feet of 13- by 13-inch flue at $1.15 per foot 23.00 20 linear feet of 8½- by 8½-inch flue at $0.40 per foot 8.00 1 8-inch thimble .60 1 6-inch thimble .40 2 clean-out doors } Damper, lintel mantel, ash dump} 65.00 ----- Total net cost [I] 369.35

[F] The prices used in this example are merely illustrative.

[G] Includes material for footing and cap.

[H] Includes labor for footing and cap.

[I] Where the chimney is built by contract, 10 to 15 percent should be added for profit and overhead.

SMOKY FIREPLACES

When a fireplace smokes, it should be examined to make certain that the essential requirements of construction as outlined in this bulletin have been fulfilled. If the chimney is not stopped up with fallen brick and the mortar joints are not loose, note whether nearby trees or tall structures cause eddies down the flue. To determine whether the fireplace opening is in correct proportion to the flue area, hold a piece of sheet metal across the top of the fireplace opening and then gradually lower it, making the opening smaller until smoke does not come into the room. Mark at the lower edge of the metal on the sides of the fireplace. 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 test; or the trouble can generally be remedied by increasing the height of the flue.

OUTDOOR FIREPLACES

Outdoor fireplaces range from simple makeshifts to elaborately equipped structures harmonizing with the architecture of the house.

No one type will meet all conditions, but all types should be practical to use and yet not be fire hazards or eyesores.

TYPES

The tendency is to build too large an outdoor fireplace. Where only a little cooking is to be done occasionally in a small yard or at a picnic, several concrete blocks or stones set on the ground about 12 to 16 inches apart will serve. The shelf of an old refrigerator may be used for a grille. If permanence is desired, the walls should be laid in cement mortar and the fireplace should have a suitable foundation and a permanent grille. An end wall is recommended to prevent embers from being scattered by drafts blowing between the side walls. Smoke annoyance while cooking is lessened by making the fireplace long enough to permit a short chimney (fig. 40).

A circle of stones laid loosely on the surface, larger stones set partly into the ground, or carefully laid masonry walls on a stable foundation may be used for campfires and small barbecue parties. A cast-iron pot with a lid can be buried in the ashes for baking. Pipe supports for pots and pans built into the masonry are a convenience; they can be homemade or purchased. Spits for roasting can be improvised or bought.

Fireplaces opening onto an enclosed porch or paved terrace, are often built as an integral part of the house chimney (fig. 41). The corner of boundary walls permits effective treatment. 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 fireplaces.

OBTAINING PLANS

Plans for outdoor fireplaces are available from various publishing houses; several magazines feature illustrations that can be adapted to the material at hand. If a structure is to be built with local labor and material, simple designs are advisable. The size of stones, joints, and proportions have a direct influence upon appearance, and good personal taste frequently results in more pleasing structures than blind adherence to conventional designs. The various combinations of ovens, cranes, grilles, storage compartments, benches, lights, sinks, etc., to be used as built-in features affect the design. Before planning a structure with these features, 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 in. Skilled labor should be employed for elaborate designs (fig. 42) when much equipment is built in or when the fireplace, as in figure 41, is an integral part of a permanent building.

CONSTRUCTION

Ordinarily the fire is built on the hearth, no grate being used. Fire regulations in hazardous localities may require firing doors, dampers, spark screens, and a solid-plate cooking surface; otherwise these features are not essential. Two and a half square feet of cooking surface is desirable, while access to both sides and the end permit several people to cook at the same time. The side walls should have fairly level tops for pots and pans. Side walls are made 2 to 6 inches higher than the cooking level to permit anchoring the grille; if too high, they interfere with cooking. Commercial grilles are available, but satisfactory ones can be made of ½-inch to ¾-inch pipe or 5/8-inch reinforcing rods. The pipes should be 6 to 10 inches longer than the width of the firebox; they should be spaced not more than 1¼ inches apart and have their tops exactly level to prevent pots and pans from wobbling. Two or three pipes can be used for a lintel over the opening into the flue if regular iron lintels are not available. Where a solid top is desired, it should be of boiler plate at least ¼-inch thick. Such plates must be stiffened to prevent buckling by alternate heating and cooling; 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 chimney.

The best draft is secured when the fireplace faces the direction of prevailing breezes and is protected from strong winds which might scatter sparks. If the fireplace is built too near shrubbery or under trees, the heat and smoke may damage or burn the foliage. A slight rise or a gentle slope that affords good drainage should be selected. Paving the ground around the fireplace, with flagstones or covering it with a layer of gravel or sand will prevent the area from becoming a mudhole or an unsightly bare spot; also, danger of starting brush fires by sparks falling from the firebox is lessened.

Fireboxes 12 to 16 inches wide, 16 to 24 inches long, and 6 to 8 inches deep with the hearth at 9 to 16 inches above the ground are sufficient for most purposes. Large fireboxes are wasteful of fuel; while, if the grille is too high above the hearth, much of the best cooking heat from glowing coals is lost. Most grilles are set 15 to 24 inches above the ground, though 30 inches may be desirable to avoid the necessity of stooping when cooking. The hearth should slope 1 to 2 inches toward the front so that rain water will drain away.

The area of the chimney flue should be at least one-eighth the vertical cross-sectional area of the firebox.

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 periods. They, or common brick linings, are advisable for the more permanent and expensive structures or where it is necessary to use porous stone, such as sandstone and most stratified rocks, which absorb water and flake or chip upon exposure to fire.

Most rocks or stone that can be worked up without special tools or skill, brick, and concrete are adaptable for the average fireplace (fig. 43). The size of the stones determines the thickness of the walls; no wall should be less than 8 inches thick.

Where suitable stone is difficult to get in sufficient quantity, 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 concrete. When flue lining is necessary, it will serve as a form for the flue: otherwise a metal stovepipe makes a practical form, or the flue can be formed of brick laid on edge. The stones can be laid and the concrete deposited with the least trouble by building the veneer and flue only 6 to 8 inches high at one time. All masonry should be laid in mortar, as described on page 10. Concrete made in the proportions 1:2½:4 will serve most purposes where wall sections are about 8 inches thick. For heavy foundations and thick walls not subject to direct fire, 1:3:6 concrete is strong enough.

A concrete slab 4 to 8 inches thick with the bottom 4 to 6 inches below the surface provides a sufficient foundation for medium-sized structures where frost is negligible and the soil is well drained and firm. If the soil is not well drained a 6- to 8-inch layer of stone, cinders, or sand should be provided under the slab and the surface of the immediate vicinity graded or otherwise protected from water. It is advisable to use ¼-inch or ½-inch reinforcing rods, 6 inches apart in both directions, one-third the distance from the top in slabs for all but the smallest fireplaces or where frost is not severe.

Heavy and expensive structures, especially those having tall chimneys, should have foundations below the surface affected by frost or erosion and strong enough to prevent settlement or cracks. Such a foundation can be made of concrete, with a liberal use of large stones for economy, extending under the whole structure, or be continuous walls with a footing similar to those used for houses. The advice and help of builders may save money in the construction of foundations of large expensive fireplaces, especially where climatic conditions are severe and the bearing power of soil is not known.

OPERATION

Cooking should be done over glowing coals, as flames and smoke smudge the utensils or even the food. When the wood is nearly charred, most of the smoke has been driven off and the chimney is hot enough to draw the smoke up the flue. All fires should be banked before they are left, to avoid setting fires. 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 earth. Water thrown on a hot fire may result in scalds from the steam and may crack the fireplace.

BARBECUE PITS

Barbecue ovens are rather expensive unless for community use. Outdoor fireplaces, without or with spits for roasting, are frequently called barbecues in some sections of the country. For occasional barbecuing parties, a hole in the ground will serve. Dig a hole several feet deep and several feet larger each way than the size of the carcass to be roasted; then place stones in the bottom to retain the heat. A trench 30 inches deep, 36 inches wide, and about 10 feet long will accommodate about 400 pounds of beef. A fire should be built sufficiently ahead of time, about 3 hours, to heat the stones and bottom and accumulate ashes for proper banking. Have someone with previous experience operate the pit, because improper wrapping of the meat and handling of the coals results in poor cooking.

DUTCH OVENS

Dutch ovens (fig. 25) are often built in connection with both indoor and outdoor fireplaces to copy early kitchen fireplaces or for actual baking.

When used as an ornament, the oven is fitted with a cast-iron door, and the space thus formed may be used for wood storage. An open firebox or compartment below may be similarly used. Spaces used for wood storage should be separated from the fireplace by a brick or stone partition at least 8 inches thick, all joints being completely filled with mortar.

If the oven is intended for baking, it is advisable to line it with firebrick, and the masonry should be at least 8 inches thick. A greater heat-storing capacity is secured by using thick walls. 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 base. The throat or dome should be carefully formed with brick molded or ground to an arch and preferably should be fitted with a damper. If the top of the oven is flat, several lintel irons will be needed to support the brick. A separate flue with a damper is recommended. For ovens of ordinary size an 8½- by 8½-inch flue is ample. The oven is preheated by fire or hot coals. Before food is placed in the oven, the coals and ashes are removed through the ash drop.

Figure 44 shows a Dutch oven made of tapered adobe bricks and plastered outside with adobe mud. A hole in the top permits the escape of smoke, while the orño is being heated by the fire built inside on the floor. This hole is closed with an adobe block after the coals are raked out. When loaves of bread have been placed on the floor with a wooden paddle, the door hole is stopped with adobe brick.

Boy Scouts and campers frequently improvise Dutch ovens by packing damp sandy clay, 8 to 12 inches thick, around a wooden barrel, a tin wash boiler, or slabs of rock to form a vault. After the earth has been gradually dried and baked with a slow fire, the oven is ready for use. The hole in the top and the door can be closed as in the orño.

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U. S. GOVERNMENT PRINTING OFFICE: 1947

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 15 cents

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Transcriber Note

The footnotes for the tables were changed from arabic numerals to alphabetic characters to distinguish them from the text footnotes.