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How to insulate behind a planned Acrylic Tub and Surround? Any advice/suggestions please.

thepirate2008 | Posted in General Questions on

Hello everyone,

We recently bought an older home in Hunterdon County, New Jersey (1930’s) and part of our initial planning was to remove the moldy tile and cracked tub that existed within the first floor of the brick home. Upon removal of the tile and cement board, there are some furring strips nailed to the structural brick (to which the cement board was attached). We were planning on placing an Acrylic tub and surround within this cavity but now that I have opened the space I am unsure what to do, should I remove the existing foam board insulation, should I replace it? The furring strips are only an inch or so in depth so there would not be much space between the tub/surround and brick wall. Appreciate any advice/guidance.

I should note that currently behind the cement board there is 1/2inch DOW Blue rigid foam insulation  placed within the furring strips (on the exterior walls).

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  1. user-2310254 | | #1

    Can you post pictures? Is this an exterior wall(s)?

  2. Expert Member
    Akos | | #2

    I'm not a big fan of spray foam, but for a tub against an outside wall in an all brick sturcutre, it is the best option. You don't need a lot, 1.5" is plenty, but you do want enough to air seal the structure, provide a bit of R value and prevent moist air from your shower hitting the cold brick. Make sure to run the SPF from floor to ceiling.

    One of the smaller 2 part kits is great for this type of job. You'll have to do a fair bit of trimming but not a lot of work for a small area. You only need to trim flush the area above the tub.

    Not cheap, but also not that expensive, for an extra bit of R value, install 1/2" Kerdi board instead of cement board for your tiles.

    A well sealed and insulated bathroom is a comfortable bathroom and will also be mold free.

  3. tommay | | #3

    Well if you are replacing the entire tub and shower with a new unit, is it possible to move the tub a little further out in order to make insulating easy? Basically, remove what is there and frame a new, square, straight and plumb wall on the outside wall portion. Then you can insulate and install the tub properly up against the studs..

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