Determining the Vertical and Horizontal Extent of a Building's Foundation
Below every visible structure lies a foundation that reaches down past the frost line to prevent shifting. To bear a building's weight over time, these foundations must remain level, which is why they rest on wider underground bases known as footers. By locating the footers, you can establish both the depth and the width of the foundation.
By Jamie Howard3 steps
A building's foundation is set atop footings, which can help determine the depth and width of a foundation.
The foundation of a building carries the structure that rises above ground. To keep a building from shifting or moving, foundations are dug down into the soil past the frost line. A foundation also needs to be level so it can bear the structure's weight across many years. For this to happen, foundations rest on larger bases set deep underground, which are called footers. You can figure out the depth and width of a foundation by finding where its footers are located.
Step 1
Excavate right next to the building's exterior. A building's foundation rests on footers, which are concrete slabs that provide support. Since the footer has to hold up the weight of the foundation, it is always wider than the foundation wall. Continue digging down until you encounter concrete; that concrete is the footer.
Step 2
With a tape measure, measure from the point where the concrete foundation emerges above ground down to the point where it connects with the footer. The resulting figure is the depth of the building's foundation.
Step 3
Dig away from the foundation in an outward direction until you arrive at the edge of the footing. Measure how far the footing extends beyond the foundation wall. Footings are usually built with a width that is twice the thickness of the foundation wall. If you double the extension you measured, which accounts for the side of the foundation you cannot see, you arrive at the width of the foundation wall.
