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Can rigid foam insulation be used on brick and mortar walls?

sburban | Posted in Green Products and Materials on

Hello, I am looking to finish my basement. I live in Chicago. 2/3 of the wall is poured concrete foundation. The top 1/ 3( which is mostly above grade) is brick and mortar. The brick and mortar section is also recessed from the face of the poured foundation by about 2in. I was orginally thinking of using ridgid foam but now after research I feel unsure about which type would best in my application. Any help would be greatly appreciated. Thank you , Steve

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  1. GBA Editor
    Martin Holladay | | #1

    If I were you, I would install a 2-inch-thick layer of rigid foam insulation against the bricks, so that the brick section of the wall is co-planar with the concrete section. Then I would install another layer of rigid foam over the entire wall (on the interior side of the concrete and the first layer of rigid foam).

    Each layer of rigid foam should be installed with attention to airtightness (using canned spray foam, caulk, or high-quality tape to seal the perimeter of each sheet of rigid foam).

    For more information on this work, see this article: How to Insulate a Basement Wall.

    You should know that when old brick walls are insulated on the interior, there is a small chance that the bricks might suffer deterioration due to freeze/thaw cycling. (The problem occurs occasionally, but only if the bricks are relatively soft and if their moisture content increases due to the new insulation.) In your case, the advantages of insulation outweigh the small risk. You can minimize this risk by making sure that the bricks are as dry as possible: repair any broken downspouts conveying roof water, for example, and remove any bushes that block sunlight from hitting the bricks.

    -- Martin Holladay

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