Suitability Of Concrete

No other material can be used so easily nor to so great advantage for foundations as concrete. Often concrete foundations may be built without using forms, that is, the ground is sometimes firm enough so that if the foundation trench is carefully dug it will serve as the form. Care should be taken when placing concrete in a trench without forms not to knock down earth from the sides so that it would be mixed with the concrete. Of course the only cases where the trench can be made to serve as a form are those where the building which the foundation is to carry is not to have a cellar underneath. In other cases if the ground is firm only an inside form will be needed.

If the foundation is to enclose a cellar or basement, the concrete must be carefully proportioned, mixed and placed and of the right consistency so that the wall will be watertight. Such an end is easy to secure if the principles of concrete practice given elsewhere in this book are carefully followed. Concrete mixtures suitable for various classes of foundation work are suggested in the table of recommended mixtures commencing on page 44.

Foundation For Gas Engine

A common example of the use of concrete for a building foundation is illustrated on the next page where suggested form and some other details for a small foundation for a gas engine are shown. The method of setting the bolts by which the engine is attached to the foundation is shown in the sketch. A template should be made of straight-grained 1-inch strips with holes bored in them slightly larger than the engine bolts and so located in this template that they are in exactly the same position as the holes in the base of the engine or other machine that is to be set. Before placing concrete the bolts are suspended from the template, heads downward, with nuts above the template and threaded ends projecting a distance not less than the thickness of the engine or machinery base. Ends of bolts should be covered so that the threads will not be filled up with concrete. Sometimes bolts are set in pipe sleeves, which allows some final adjustment when setting the engine if the template has not been accurately made. Afterward the pipe sleeves are filled with a thin cement mortar or grout.

Forms and other details for a foundation such as would be used for a small gas engine.

Footings

All foundations should be planned with proper regard for the weight of the building or structure which they are to support. If the soil is not of the firmest or if the excavation cannot be carried down deep enough to reach firm bearing soil, then it is necessary to start the foundation with what is called a footing. This is a course of concrete which may vary from 10 to more inches wide and from 6 inches upward in thickness so as to distribute the load of the building over a greater area of ground. After concrete for the footing has been placed, forms are set up a distance apart corresponding to the thickness of the foundation wall, and concreting continued.

Watertight Foundations

Where watertight construction is important, one other precaution in addition to correct methods of proportioning, mixing and placing of concrete must be observed. That is, care must be taken to secure perfect union or bond between different batches of concrete or between the portions of the work representing concreting done on two different days. If this is not done there will be leakage through a seam or joint otherwise formed. If it is necessary to stop work at any time, concrete should be slightly roughened in the forms by scratching with a stick, then when concreting is resumed this surface should be brushed, washed clean, and painted with a paint of cement and water mixed to about the consistency of cream. New concrete should be placed before this paint has commenced to harden. If the above work is properly done there will be no leakage.

Simple form for concrete foundation wall where only an inside form is necessary.

Forms for a foundation wall where both inside and outside forms are necessary.

This form is set up from the bottom of the excavation so as to allow for the placing of concrete to form a footing for the wall.

Concrete gate posts with electric light fixture at the top. This work was all done by school boys.