Foundation work starts by re-establishing the building lines on the batter boards. This is done by replacing the mason’s line in the grooves cut in the batter boards.
A plumb bob is dropped at their intersection to locate the building corner (which is also the foundation wall corner), and a stake is driven at that exact location as a marker, as shown in Figure 1.
When all the corners are located, the house dimensions are checked against the distances between the stakes to make sure everything is still as accurate as when originally measured prior to excavation. The next step is to locate and build the footing formwork.
Figure 1 - Plumb bob at intersecting mason's lines
Building the Footing Forms – Outside Perimeter:
Footing forms can be trenches dug on the soil or built up wood forms. Pouring footings in a trench is possible if the soil is firm and capable of holding a sharp cut. In loose soils, such as sands, gravel, etc., this method cannot be used, as shown in Figure 2.
Figure 2 - Using a trench or wood form for footings
The stakes just driven represent the corners of the foundation walls. Footings, however, project a distance outside these walls, and their location also has to be established. The building corner stakes are used as reference points. Our sample house has foundation walls that are 8 inches thick and 4 feet high resting on 8 inch high and 16 inch wide footings, as shown in Figure 3.
Figure 3 - Foundation wall sitting on footing
From one corner stake (we’ll call it stake A), measure the distance that the footing projects outward from the foundation walls, that is 4 inches, and add to this dimension the thickness of the form board you are using that is 1 1/2 inches (a 2 inch board is actually 1 1/2 inches thick). Be sure to make this measurement 5 1/2 inches in both outward directions at each corner and drive a stake at each, as shown in Figure 4.