# Can foam sealer be used to seal the spaces in concrete block?



## Termite (Apr 13, 2008)

I guess it would serve your purposes, but you'll need lots of foam. Get the highly expansive stuff and plan on being at it a while. You'll likely need to install it in "lifts". Start at the bottom and build up from there. There are some better products than great stuff available that will be easier to use. They're sold as cartridge cans of foam that screw into an inexpensive foam gun with a metal nozzle. A good building supply center should have it. Not sure of the cost comparison to great stuff, but much easier to use, and it comes out of the nozzle a lot better.

There's a product called "icynene" (sp?) that is essentially the same thing. It is sprayed by insulators into a void and it expands to fill the void. Not a DIY thing though.

I don't know how much benefit you'll see from doing this. It certainly won't make it worse though!


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## Termite (Apr 13, 2008)

Steer clear of electrical boxes and sources of heat, such as flues for stoves, furnaces, or water heaters. Spray foam is highly combustible. 

If it gets into the electric boxes when it expands, just scrape as much of it as you can out of the inside of the box.


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## Maintenance 6 (Feb 26, 2008)

I highly doubt you'll be able to put it in one hole and have it expand over that distance. As termite said, you'll need to do it in several lifts. Another thing is that block cores don't necessarily line up vertically. You certainly will end up with voids that won't fill. One more problem, as I see it, is that concrete is very conductive. If you could fill all the voids, the webs in the block will continue to transfer heat/cold from inside to outside and vice versa. Covering the block with foam board will provide better results. You'd need to cover the foam board though. It's not safe to leave it exposed. If on the inside, cover it with drywall, or on the outside with siding.


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## concretemasonry (Oct 10, 2006)

Filling the cores of a block wall, especially without commercial equipment is too costly to justify the cost. - Especially if you plan to live in it for a couple of years. It is just like trying to justfy great windows when you really cannot accurately measure the savings.

Rigid foam insulation is the only way to go for your situation, but that is not cheap. What do you plan to do with the house in a few years - sell it of level it?

Dick


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## kc5oh (Jan 28, 2008)

That sounds like too much. I'm with concretemasonry on the rigid foam. If the house is that small you could use furring strips and panels.

And also, for the love of the FSM, do not use hardening foam if you do go that route.


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## marksto (Apr 18, 2008)

Thanks very much for all the opinions and information. Rigid foam and the effort behind it is also a bit much, so I guess I'll just plan to make do with the hollow walls for now.


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