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Old Home Bathroom Reno

Lisa Martin | Posted in General Questions on

Thanks for any suggesWhat is a good old bathroom exterior wall progression method (1947 home in Edmonton, Alberta) ?

From outside to inside: cedar siding, then 2X6 Douglas Fir planks, 12″ studs.

What would be a good insulation choice?

What would be a good baker board choice?

What would be a good drywall choice?

Should a vapor barrier be used?

Will also be installing a bathroom fan- horizontal exhausting through exterior wall due to possible vermiculite/asbestos in attic. What would be the specs for this? It is difficult to find information for this unusual location.
Thanks for any suggestions!

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, I'm not sure what you mean by "12-inch studs." Do you mean that you have 2x12 studs? (The seems unlikely.) Do you mean that you have 2x4 studs that are 12 inches on center? (That's possible, but unusual.) Or was that a misprint?

    Your reference to "baker board" sent me Googling, since I've never heard of the product. My search came up dry, and then I realized that you probably mean "backerboard" (underlayment for tile). Am I right?

    Almost any type of insulation can work, so I'm not going to tell you what to use. Here are some basic principles:

    1. Ideally, you want to at least meet minimum code requirements for R-value in your climate zone. In colder climates of the U.S., most up-to-date codes require a minimum of R-20 or R-21 for above-grade walls.

    2. Ideally, your insulation plan will address thermal bridging. This can be done with a layer of continuous rigid foam -- in your case, it would probably be installed on the interior -- or with the "Mooney Wall" approach (using horizontal 2x4 strapping on the interior side of the studs).

    3. Your insulation must be installed with attention to airtightness. If you choose to install air-permeable insulation like fiberglass, mineral wool, or cellulose, you'll need an interior air barrier.

    For more information on tile backerboards, I suggest that you read Tile Backerboard Options.

    If you are asking about drywall as well as backerboard, I'm guessing that some areas will have wall tile, and other areas will have drywall. Most builders use moisture-resistant drywall in bathrooms, but there are paper-free drywall options if you are worried about moisture.

    Your wall assembly doesn't need a vapor barrier, but it will probably need a vapor retarder. For more information on this issue, see Do I Need a Vapor Retarder?

    Most bathroom exhaust fans can be easily mounted in a wall. Panasonic fans have an excellent reputation; the Panasonic WhisperWall model is designed for wall mounting. Here is a link to the installation instructions: WhisperWall Through-the-wall fan.

  2. Lisa Martin | | #2

    Thanks Martin!

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