Knowing the width of a foundation is important in the construction process of a home or other building. A foundation supports a structure, so knowing the width is a piece of information necessary to know the bearing capacity of the foundation. It is also necessary to know the dimensions of the foundation when having repair work done. Contractors will need to know its size in order to give you an estimate for the cost of the work.
Determine the shape of the foundation. If the foundation is rectangular, calculating the width can be done in one step. However, if the foundation is an odd shape, you must take the width of each section of the foundation.
If the foundation is rectangular in shape, stand in front of the foundation and, using a tape measure, calculate the entire width from the foundation's outer left wall to the outer right wall. Having a second person to hold the tape measure as you stretch it across the foundation will make this process easier.
If the foundation is broken up into two or more pieces, such as a porch off to the side of the house, take the tape measure and first measure the width (left to right when standing in front of the house looking at it straight on) of the main structure. Then, measure the width of the porch area and add it to the width of the main structure. Make sure the widths do not overlap, however. You want to have one width for the entire house.
Look on your county auditor's website to see if your house's or business's site plans are available online. The site plans may list the width of the foundation.