PROJECTS IN CONCRETE CONSTRUCTION 157 



be exactly 5 feet. For convenience and accuracy, any 

 multiple of 3, 4 and 5 may be used. 

 Working Instructions: 



1) Carefully excavate all soil to proper depth. If the soil 

 is firm, it may be used as the outside form up to the 

 surface, above which a double form will be necessary. 

 For all kinds of foundation walls, it is always essential 

 that the footing be wider than the wall proper, and 

 that it be carried deep enough to be below the frost 

 line. If double forms are necessary, due to the soil 

 caving it will have to be excavated to a greater width. 



2) Construct the form with care, duplicating the inside 

 and outside wall dimensions as desired. See that cor- 

 ners are square, walls are well braced, vertical, and 

 carefully aligned. If walls are to be more than six 

 feet high, tie wires should be used in addition to the. 

 supporting braces (Fig. 152) . If this precaution is not 

 followed, a bulged wall is likely to be the result. The 

 inner form on a hot-bed or other small piece of con- 

 crete work, may be supported by braces on the inside, 

 running from one wall to the opposite one. 



3) For thin walls up to six inches, a 1 : 2 : 4 mixture should 

 be used. Walls more than eight inches thick may be 

 made of a 1 : 2-1/2 : 5 mixture. 



4) For a job of this kind, the concrete may be mixed to a 

 slightly wet consistency. Care must be exercised to 

 avoid the separation of the coarse material from the 

 fine, which is possible in a wet mixture. Shovel the 

 concrete into form and force the coarse aggregate back 

 from the surface of the wall by means of a spade or a 



