This section is from the book "A Treatise On Architecture And Building Construction Vol2: Masonry. Carpentry. Joinery", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
20. In cities and towns of good size, it is customary to have the building lines laid out by an engineer; but in country work - remote, possibly, from professional talent of that sort - the architect himself is often called upon to lay out the lines of the building.
The plans of the building show the area, and the sections or elevations show the depth of the excavations.
The Figures on the foundation plan should be carefully checked, as any error made at this stage of the work is difficult to rectify afterwards.
The outside lines of the building proper should be run first, and stakes driven at each corner or angle. Cords should then be stretched from these around the foundation site, and the lines for the footing courses measured off according to the distance the footings project beyond the foundation walls. By driving stakes also at the corners of the footing courses, and stretching cords from each footing-course stake to the next, the area to be excavated can be ascertained.
The portion of the building required for cellar, as well as the footing courses required for the portion having no cellar, must be excavated to the proper depth.
21. The usual depth of cellars for dwelling houses should not be less than 8 feet from the under side of the first floor beams, and more where the house is to* be heated by a furnace, in order to give sufficient height above the furnace to allow a proper ascent to the hot-air pipes. For store, office, and manufacturing buildings, the depth is greater, varying according to the nature of the business carried on, or the requirements of the occupants. In some of the large office buildings in cities, there are no less than three cellars: basement, cellar, and subcellar, and the excavations vary from 25 to 60 feet in depth.
22. Care should always be taken, in case there is no cellar under a building, to have the excavation in the trenches go down below the frost line. This depth varies in different parts of the country, but in the Eastern and New England states 4 feet is considered sufficient for ordinary buildings, if the subsoil is satisfactory. If the foundations are not started below the frost line, the alternate freezing and thawing of the earth tends to throw the walls out of plumb, and will eventually destroy them, and also rack the superstructure. This subject will be more fully explained under "Footings."
23. When the nature of the soil is such that piles must be driven to carry the building, it is customary to excavate to water level before driving the piles. This is done in order that the heads of the piles may be cut off at the water line, it being necessary that the piles be wholly under water to prevent decay.
24. In excavating cellars, it is customary to leave a runway; that is, a part of the ground is sloped down from the bank to the cellar bottom, for the more convenient removal of the excavated material. In very deep cellars covering a large area, this runway is usually built of heavy plank supported on wooden beams and posts.