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What is the best way to insulate an exterior wall with a shower on the inside & another shower on the outside?

Eldee58 | Posted in GBA Pro Help on

What is the best way to insulate an exterior wall with a walk-in shower on the inside and an outdoor shower against it on the outside?

We are in the process of repairing our Hurricane Sandy damaged home on the New Jersey shore. We took the 1st floor down to the studs and are putting it back together now. In the bathroom, we removed the tub and tile surround, to replace with a walk in shower, and discovered that the exterior wall was totally rotten. We replaced the exterior plywood, studs, vinyl window and re-sided with tar paper and fiber cement siding. The outdoor shower is also located against this wall. (We can’t really move the outside shower because the concrete in this area was poured with a good pitch that drains the water away nicely). The interior side of wall (including the window) is the 5′ wall of the shower. On the inside wall, I was planning to install Hardie Board and 12″ tiles. I’m really confused about what I should do, insulation/moisture barrier wise, between these two walls. With showers on both sides, the potential for a wet wall seems high. Any thoughts would be greatly appreciated! Thanks much, LaurenD

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, you never want a window in a shower. If you used to have a window in your old shower, that may explain why "the exterior wall was totally rotten."

    Second, you can choose from a wide variety of insulation materials. Your problem isn't really insulation; it's water management. If you are an experienced tile setter who knows how to detail a tile shower, you are all set. If you aren't, you need to study up on the topic, or hire a contractor who understands this work.

  2. Eldee58 | | #2

    Thanks for your reply. I'd rather not have a window in the shower either but that is the way the house was built. However, it is the only source of natural light for the bathroom and I hate bathrooms without natural light. The bathroom is sandwiched between the kitchen and a bedroom. The bathroom size is 5' x 10.5' with the window at one end and the door at the opposite end. Not a lot of flexibility in the given space, hence the challenges!

  3. GBA Editor
    Martin Holladay | | #3

    Your answer is ambiguous. You wrote, "I hate bathrooms without natural light," but also, "I'd rather not have a window in the shower."

    It's extremely difficult to detail a window in a shower stall in such a way that water doesn't enter the wall. It's up to you to decide what matters more -- natural light in your bathroom, or a wall that isn't rotten.

    Remember, you are in the process of remodeling. Your statement "that is the way the house was built" is irrelevant. If the house had a mistake, there is no need to repeat it.

  4. user-946029 | | #4

    Is a skylight a possibility? Yes, it's a hole in the envelope, but at least it won't get as much water exposure as a shower will.

  5. heidner | | #5

    Solar tubes can easily bring in all the daylight you need for a bathroom. We've done that on two of our bathrooms - moving a light fixture into the solar tube. The light can be more even in the bath room with the tubular lights -- after moving away from a small bathroom window...

  6. user-659915 | | #6

    Windows in shower enclosures are really not that difficult to detail properly so long as the shower enclosure is not tiny. Just take the obvious precautions and don't place the window right beside the shower head's main impact area. We generally use acrylic block operable casements in vinyl (I know) frames - these minimize the potential for condensation problems and can give you that outdoor shower feel even when you're inside. Even better if it's a doorless shower enclosure.

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