How much does it cost to waterproof a basement or foundation? – Square footage, depth, and other considerations

Waterproofing the basement of a home or business is an important investment every owner should make. As with other investments, choosing the cheapest option often turns out to be a bad choice in the long run.

Of course if you don’t understand much about waterproofing and building, it’s easy to run the decision through the cost filter then decide on that one factor.

This is why it is important to gather as much information as possible. With this information you can make better decisions and invest wisely.

One of the key dimensions that your waterproofing company will need is the square footage of your basement, the external/perimeter measurement of your foundation, and the depth of your foundation.

How do I know the square footage of my basement?

All of these dimensions are easiest to find if you have the blueprint of your home or planned home.

If you don’t have it, your local zoning board or similar agency, located in city hall, likely has a copy of it on record.

Of course, there is a simpler way to go about finding the square footage or your basement.


If you are lucky enough to have a square and empty basement, this is easy. Measure the length of one side in inches, then measure the length of the next side. Multiply those two numbers together. Divide by 12 to get the final square footage.

But what if there are bump-ins, carve-outs, walls, and more? When things get tricky, there is a more comprehensive guide here:

How do I measure the perimeter of my house?

Again, gather your tape measure. This time, you will be working outside of the structure.

Again, it is easier if it is a square.

Measure one side in inches, then measure the adjacent side in inches. Then measure the third and fourth sides. Then simply add these measurements together. Divide by 12 to get the final measurement in feet.

One word of caution. My porches and patios can look like they are part of your house, but they do NOT have foundation under them. They do not need to be measured to be part of your perimeter for waterproofing purposes.

How do I measure the depth of my foundation?

This is perhaps the simplest of all the measurements.

At each window or other location where a pipe, vent, or wire goes through the foundation from inside to outside, you will need to make a measurement.

First, measure the distance inside from that window, pipe, vent, or wire to the floor of your basement. Do this for every one of those items.

Then go outside and for each one of them take a second measurement. Measure the distance from the ground to that extension.

So if you have a dryer vent, it might work like this:

  1. Measure the distance inside from the vent to the floor. (Let’s say it’s 65 inches.)
  2. Measure the distance outside from the vent to the ground. (Let’s say it’s 8 inches.)
  3. Subtract item B from item A. (In this case 65-8=57)
  4. Your foundation is 57 inches deep in that location.

The more of these measurements you can give your waterproofer the better.

If you are using a calculator before contracting with a waterproofer, you will need the average depth of your foundation. Add these measurements together, then divide by the number of them.

This will help get you a good estimate of the average depth of your foundation.

With these measurements you are better prepared to approach your waterproofing companies and seek estimates for this important investment.