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Community and Q&A

Spray foam for a concrete brick house

4BrJ9ioRhU | Posted in Energy Efficiency and Durability on

I plan on spray foaming my house really soon. it’s a post-WW2 home with concrete brick as an exterior cladding. I have read the article on the precautions of insulating brick homes, but there is a slight difference.

1. Are concrete bricks generally more resistant than clay bricks to spalling?

This house has the joists embedded into the foundation wall. I don’t want them to rot. I am assuming that if I cut them off, the new basement structural wall would need a thicker slab to rest on than i currently have. The basement is finished, so that is out. I also can’t run any pipes, so that is out

2. I wanted to know the method of how one treats wood with borates? Even if treated, won’t the borates leech out with moisture?

3. In addition to (2), I guess the only other option (unless someone can ring in here), is to create a small thermal bridge in addition to the wood itself. I was thinking, maybe aluminum downspout straps can nailed close to the end of the joists. But i don’t want too much heat loss

Is there any other method someone can think of?

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  1. 4BrJ9ioRhU | | #1


  2. user-659915 | | #2

    are concrete bricks generally more resistant than clay bricks to spalling?

    Generally, yes but the composition of concrete bricks can vary significantly. If it's possible to find the manufacturer they may be able to answer more specifically. Otherwise ask your local inspections dept. and local contractors to see if anyone has specific experience to share. Also, what is your location? Spalling is a problem of harsh climates and is worse in walls with high weather exposure.

    In response to your other concerns, your best bet is to work with a specialist local contractor with long experience of this kind of work and first-class references. If you can't find one, you may want to reconsider the whole spray foam idea. If you get it wrong it won't be an easy or inexpensive fix.

    By the way, the aluminum strap idea, while ingenious, is definitely not going to work. Intentionally leaking tiny amounts of heat to the encapsulated ends of your joists will not prevent rot if they become damp for any reason.

  3. 4BrJ9ioRhU | | #3

    I live in a cold climate, about 4000 metric heating degree days, moderately wet, Toronto, On.
    the issue with rotting has to do with the beams getting cold, from a reduced vapour drive due to higher insulation in the wall, the external parts of the wall get colder. Heat does dry things out. A clothes dryer works on the same principle. it works on a micro scale too, and that is the point of that article.

    I was wondering if the strap was too big of a heat sink, maybe 3" long nails? I think i want to do this in addition to borates. I am considering modelling the straps in THERM.

    Would taking household borax mixed with water and painted on work?


  4. GBA Editor
    Martin Holladay | | #4

    1. Is this a wood-frame house with brick veneer or a masonry house with load-bearing brick walls?

    2. If you end up hiring a consultant, I recommend that you talk to someone at the Building Science Corporation ( As James mentioned, when you are insulating a brick house, it's easy to make a mistake that will lead to expensive problems.

  5. 4BrJ9ioRhU | | #5

    1. answer: masonry with load bearing concrete brick (not clay) and concrete block
    2. considering it.

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