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How to Fill Gaps and Cracks with Foam Sealant

A man using spray foam to seam up the jam/frame in between a wall and a door.

Your home may look perfectly secure from the outside, but each year, tiny gaps and cracks open up around doors, windows, and other entry points. Anywhere walls and other features meet can also end up developing cracks as the structure ages and settles. These cracks let air escape from inside the home and flow inside from the exterior, raising your energy bills year-round. Gaps also let pests like insects and mice move in right where you don’t want them. Expanding foam sealant is a quick solution to any irregular gap between solid materials like concrete, wood, siding, and roofing. Use it correctly for a well-sealed gap that looks nice with no mess or fuss.

Invest in Solvent and Gloves

A person putting on blue latex gloves before working with harsh chemicals

Don’t spray the smallest blob of foam sealant before having a plan to clean it up. It’s easy to assume that the pointed nozzles on these products will give you perfect control and therefore eliminate any chance of a mess. In reality, it’s all too easy for your grip to slip or the foam to drip during application. Only a foam sealant solvent will clean up the mess properly, even on your skin. The solvent is a little harsh to use on bare skin, so consider wearing disposable gloves instead. These solvents will still damage painted surfaces and many types of flooring. Tape and plastic sheets are recommended anywhere spills or drips are a major concern.

Know When NOT to Use It

While expanding foam sealant is a fast way to close up gaps outdoors and in unfinished parts of the home, it’s not ideal for all uses. Avoid using this kind of foam for:

Wait to Sculpt and Clean

A close up image of a person using a orange utility knife to scultp down spray foam in a door frame

Since the foam is soft and wet until it has a chance to cure, many people immediately try to sculpt and shape it as desired after spraying. This is a mistake, even if you’re trying to clean up a drip or spill. Unless you’re soaking the foam in solvent immediately to start cleaning it up, wait until it cures and hardens. It’s far easier to cut and shape the foam as needed at this point, and it’s fine to wait to clean up drips and spills until that point as well. Attempting to move or spread the foam with tools will just smear it and coat everything you’re trying to use.

Cover to Protect It

Adding beige siding to a barn style house using scaffloding

A filled gap won’t let drafts in and out of your home anymore, but how long will the gap stay filled? Make your work last by covering the foam in some way after it’s cured and shaped. Shave down any protruding foam with a sharp utility knife or a straight edge. Most expanding foam sealants are easily painted or sealed with any exterior products, and this kind of coating will protect the material. To keep it from being crushed or burrowed through by insects, consider a harder and more durable covering. Layers of metal roof flashing, siding, or wood trim can all protect gaps filled with spray foam so that the drafts don’t return for decades.

Check the Expansion Amount

A woman holding a can of spray foam with the nozzle pointed at plumbing fixtures on a bathroom sink.

It’s a common impulse to grab a can of expanding spray foam when you discover a gap spreading around a window or door opening in particular. While this kind of foam can work just fine in these instances, high-pressure foam is not a good idea. Look for low to medium expansion foam only when closing gaps and cracks around doors and windows. High-pressure foam is often strong enough to push a frame out of alignment, making a window difficult to open or causing a door to stick. The low-pressure foam will fill the space just fine without the risk of changing the alignment or function of the fixture. You may have to apply a little more, so take your time and build in layers rather than trying to close the entire gap at once.

Don’t let gaps and cracks make your home hard to heat or cool. Pick up a few cans of expanding foam sealant from Do It Best Hardware and solve your draft issues once and for all.

While do-it-yourself projects can be fun and fulfilling, there is always a potential for personal injury or property damage. We strongly suggest that any project beyond your abilities be left to licensed professionals such as electricians, plumbers, and carpenters. Any action you take upon the information on this website is strictly at your own risk, and we assume no responsibility or liability for the contents of this article.