DISCUSSION OF DETAILED DESIGN 



FOUNDATIONS 



Fireplaces which are constructed of loose 

 boulders (pi. I, fig. 1) require no foundation. 

 The lower stones should be set into the ground 

 approximately one-half of their depth. 



All stoves and fireplaces of masonry con- 

 struction should set upon a concrete or a 

 masonry foundation. 



The foundation may be of two kinds: 



(a) A reenlorced concrete slab which does not extend 

 below the frost depth (pis. II, IV, and VIII). 



(b) A concrete or masonry foundation which extends 

 below the frost depth (pis. XI and XII). 



In locations where it is not practical to con- 

 struct concrete foundations, the grate shown in 

 plate III may be anchored with a "log dead- 

 man" as shown in figure 6. 



The concrete slab must be properly reen- 

 lorced with wire mesh or bars, in order to 

 prevent any rupture from frost action. The 

 foundation which extends below the frost line 

 need not be reenforced, and may be con- 

 structed of stone, brick, concrete, or cement 

 block, or any similar material which is avail- 

 able in the locality. 



In constructing the foundation, a pit of the 

 proper dimensions is excavated. The reen- 

 forced concrete "floating pad" should rest 

 upon the natural subsoil. If any fill is necessary 

 on which to construct the reenforced concrete 

 pad, it should be limited to a few inches {other- 

 wise another location should be selected), and 

 this fill should preferably consist of masonry, 

 although it may be laid "dry" if thoroughly 

 compacted. 



For the foundation which extends below frost 

 depth, the bottom of the pit is filled with a mix- 

 ture of concrete into which "spalls" may be 

 thrown. The material is thoroughly tamped and 

 the concrete constructed upon it. 



The concrete mixture should be as follows: 



(a) Where screened aggregate is used, the mixture 

 should be one part cement, two parts sand, and 

 four parts of coarse aggregate, graded to a size of 

 approximately 1 inch. 



(b) Where unscreened aggregate is used, the mixture 

 should be one part cement, and six parts of pre- 

 graded gravel with a maximum size of gravel pass- 

 ing a I' S-inch screen. 



If the fireplace is generally low, and there is 

 no excessive weight at one end, which might 

 cause the structure to settle unequally, a re- 

 enforced concrete "floating pad" is sufficient 

 for all normal requirements (pis. II and IV). 

 The average height of the low fireplace includ- 

 ing this proposed foundation is approximately 

 24 to 30 inches. The resulting weight per square 

 foot approximates 480 pounds. Average clay 

 soil is capable of supporting approximately 1 

 ton per square foot, or four times this load. Inas- 

 much as the average site chosen for a fireplace 

 is on the firmer soils, the normal weight is far 

 below that which the soil is capable of support- 

 ing and therefore, the question of foundations 

 in the majority of these fireplaces, even where 

 extreme temperatures are experienced, is one 

 of providing a footing which is properly reen- 

 forced near the upper surface (pi. IV, fig. 4) to 

 allow for the heaving and settling of the fire- 

 place as a unit. 



In most of the larger camp stoves with a 

 chimney, where excessive weight occurs at the 

 chimney end, the foundation wall should extend 

 below the frost line (pi. XI). 



FIREBOX 



The size of the firebox has a direct bearing on 

 fuel consumption. In areas where fuel is scarce 

 and charcoal is used, its size should be kept to 

 the minimum dimensions (height 6 to 7 inches, 

 length 18 inches, width 12 to 14 inches). It is 

 also desirable when charcoal is used as a fuel, 

 to so design the firebox that there is a small 

 opening in the bottom of the firebox through 

 which the necessary draft may be created, to 

 cause the necessary combustion in charcoal. 

 The firebox in the camp stove (used for cooking 

 only) requires less width than the firebox in 

 the fireplace (used also as a warming feature). 

 The cooking surface should be of sufficient area 



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