The composition, characteristics, and method of making and laying concrete are given in Part III.

The great use of concrete for foundations is generally to form a solid base or platform, which will cause the weight of the building to be distributed over a larger area, and thus reduce the pressure on each superficial foot to whatever the soil is able to bear.

To ensure the stability of the bed of concrete itself it must be composed of such materials, and be of such a thickness, that in case of the subsoil yielding it will settle uniformly in one mass, and bear the cross strain upon it without breaking; care should also be taken that its composition is such that it is in no danger of crushing under the weight brought upon it.

The various cases in which concrete is useful have been considered in the preceding sections.