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Community and Q&A

Can I frame over blanket insulation and vaper barrier in the basement and get proper Fire Blocking?

R. S2 | Posted in Building Code Questions on

I would like to leave the insulation blanket and vaper barrier in place when I frame the walls in my basement. Is it permissible to frame out from the insulation and then place the horizontal fire blocking every 10 feet by just compressing the insulation with 2x lumber against the concrete?

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    R.S. 2,
    First of all, can you tell us your name?

    When you refer to "the insulation blanket," I assume that you are talking about fiberglass insulation wrapped in a polyethylene or vinyl jacket. This type of insulation is considered obsolete for the interior of basement walls. It shouldn't be used in that location. Instead, you want either rigid foam or closed-cell spray foam. For more information, see this article: How to Insulate a Basement Wall.

    For details on the fire blocking requirements in your area, talk to your local building inspector. According to my understanding, when fire blocking is required for a stud wall adjacent to a basement wall, the fire blocking has to extend all the way back to the concrete, with no intervening insulation.

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