You can use spray foam for repairing foundation cracks to prevent water from entering a basement and causing bigger problems, unless there is a larger underlying issue that needs addressing. 

Many minor cracks in your basement or crawl space walls would be ideal candidates for treatment with spray foam. Concrete cures and settles over time, so the appearance of cracks is oftentimes quite normal and usually no cause for alarm.

However, you can’t use just any can of spray foam from the hardware store, and in some cases, it might be wise to seek the advice of professional structural engineers. 

Here’s our guide to using spray foam to fill foundation cracks.

Can You Use Spray Foam For Foundation Cracks?

The general rule is that if your concrete crack is less than a quarter of an inch in width, then it’s likely to be a minor shrinkage issue, especially if it is under a basement window or over a doorway, and so spray foam would be a good product to use in this case. 

One of the best benefits of using a polyurethane spray foam is that it will penetrate right through the concrete wall, which means that you will not need to dig out the external face of the crack. The foam will expand all the way through, sealing the entire depth of the crack from front to back.

Settlement, or minor curing cracks are not uncommon in residential construction where control joints are seldom used to give concrete somewhere to release this energy. Anything wider than a quarter inch, or more extensive, perhaps the crack runs from top to bottom, or at an angle from one corner, should be checked by an engineer.

What Spray Foam to Use?

Spray foam technology has developed to the point where there is now a range of products specifically designed to fill this niche. Most present as a liquid polyurethane component that will use water in the crack as the catalyst for expansion. 

Benefits Of Using Spray Foam For Foundation Cracks

Spray foam bonds incredibly well to concrete, and expands to fill every air gap, every tiny space inside the crack. 

It will expand to up to 30 times its volume and will push out into any external soil void, augmenting any loose fill.

Its closed cell structure will form a watertight seal, blocking out any further water ingress.


It is probably a good idea, if there is water ingress, to survey the outside of the property to see if there is any way water can be diverted away from the area of the foundation. Perhaps the downspouts require clearing out, or extending? Or maybe the soil grade around the property is sloping the wrong way?

Can You DIY it?

You can DIY crack repairs with spray foam as long as the cracks are minor. In fact, fixing a minor crack quickly with spray foam could stop bigger problems further down the line should water ingress continue to be an issue.

A high moisture level is one of the key contributors to mold growth in a basement or crawl space, so tackling the problem with a good polyurethane spray foam is a good idea.

How to Use Spray Foam For Foundation Cracks

Let’s assume you have sourced the correct spray foam from your hardware store. The next thing to do is to ensure that you have all of the recommended personal protective equipment.

Spray foam is sticky and will react to moisture, so make sure you have a pair of single-use gloves as it is unpleasant cleaning it off your skin.

For the same reason, it is advisable to wear a good set of protective goggles. Your hardware store will probably stock some that will fit over your spectacles too, should you wear them.

A mask is also essential when you are working in an area with low ventilation, such as a crawl space or basement.

Once you are all dressed up then the next thing to do would be to clean up the area where the spray foam is to be applied.

Lay something out below the crack to catch any spillage, to make clearing up easier. The more junk and mess that gets left in a crawl space, the easier it is for mold and rot to thrive.

Use a brush to probe into the crack to release any loose dirt or concrete dust.

Starting at the bottom of the crack, push the delivery tube of the spray foam as deep as you can into the opening and fill slowly all the way to the top.

The spray foam will begin to cure, expanding and filling all available space, within seconds.

Tips to Make the Job Easier!

If there is water running into the basement or crawl space through the crack you want to fill, then stop. The first thing you need to do is ensure the water is either stopped or diverted away from the working area.

Spray foam on its own won’t stop a determined leak and if you try, then you will likely end up with a mess.

Make sure you have a decent light source so you can see what you are doing. A pocket torch will likely create too many shadows for you to be able to see what you are doing.

When You Shouldn’t Use Spray Foam For Foundation Cracks? 

If your concrete has opened up a crack that is wider than a quarter inch, it is likely that simply filling the crack will not be enough. Settlement or subsidence is a problem that could threaten the structure of the house.

An engineering professional should be called out to carry out a full structural survey to advise on what can be done to prevent the condition of the concrete foundations from deteriorating further.

Are There Better Alternatives To Fix Foundation Cracks?

Alternative 1. Epoxy resin

Basically, it is a resin that is injected through a port directly into the crack once it has been sealed with hand-mixed two-part epoxy on the surface. Ideal if the area is dry and you have good access to the working area.

It takes time to cure, and you will need at least two days to complete the job, with the crack remaining perfectly dry throughout.

Perfect for filling stress cracks on a basement floor, or anywhere that may be a heavy traffic area.

Alternative 2. Masonry repair caulk

If you have access to the exterior then caulking the crack is a fast way to ensure water won’t get through, but it won’t penetrate below grade, so there will be some digging to be done if this method is to be fully effective.

Great when you need to make a repair in a hurry. 

Alternative 3. Hydraulic cement 

If you have severely waterlogged ground then you could use hydraulic cement that sets within five minutes. It is used for pool repairs and is good both above and below grade. Ideal if you are a fast worker, but it does need a lot of preparation to ensure the surfaces are clean, and there may be digging involved.


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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