Building House Foundations
Foundations. Trial holes should always be bored over a proposed building site for the purpose of finding out its exact nature, and this will sometimes prove an additional advantage to the client, as suitable sand and gravel may thus be found that can be used for the mortar and concrete, thus saving the cost and cartage of obtaining it from elsewhere.
Each individual case must be treated on its own merits, but excavations in most instances should be continued until a firm foundation at least three feet six inches below the surface of the ground is reached.
Buildings are sometimes erected on reinforced concrete rafts, which have been found necessary owing to unusual local conditions; in other cases timber or concrete piles have been used, while brick piers connected by arches are both economical and satisfactory.
The base of all walls should be formed with projecting footings twice the thickness of the wall, in order to form a wide base (like the feet of human beings and animals) on which to spread the weight; and beyond this the concrete should project six inches on each side as seen in pictures 23, 25, 26, 27 and 28.
Portland cement concrete should generally be used in foundations, and should not be mixed in less proportions than one part of cement to six of aggregate, the latter being composed of hard gravel or bricks broken to pass through a two-inch ring, sufficient sand being added to fill up the interstices. Good blue lias, or other hydraulic lime, may sometimes be substituted for Portland cement.
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