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I have just had a SIP panel building constructed and concerned about a bathroom tile install.

user-3368124 | Posted in Green Building Techniques on

I have just had a SIP panel building constructed and concerned about a bathroom tile install.
Master shower tile wall will be attached to Durock. …
Should I put air space between Durock and OSB SIP wall? or possibly ice and water? or should we just attach Durock to OSB ?

SIP panel company is EPS – They had no strong opinion.

Thank you – Howard from Sturbridge MA

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  1. user-2310254 | | #1


    I would install a waterproof membrane such as Schluter-Kerdi over the cement panel. The system is pretty straightforward.

  2. user-3368124 | | #2

    Thank you - to be clear, from OSB side
    OSB - Schulter membrane - Cement board - tile ??
    Thx, Howard

  3. FourForHome | | #3

    Howard, I have a tiled shower against a SIP wall and the cement board goes against the SIP and then the Schluter membrane, then tile. (OSB - cement - membrane - tile) Just remember that the SIP osb doesn't have the same holding strength as a stud. Be generous with the screws.
    Durock also has a membrane/shower system that seems to cost a bit less than Schluter.

  4. user-2310254 | | #4

    As Mark indicated, the waterproof membrane is installed over the cement board. You could also use a fluid-applied system such as Redguard.

  5. ohioandy | | #5

    Even better, Schluter makes it very clear that their membrane system can be installed over standard drywall--it doesn't have to be moisture resistant, let alone cement board. I often use 1/2" Fiberock, a gypsum product which seems to have more stiffness than drywall, and can extend past the Schluter membrane and be painted like drywall. Using actual cement board with Schluter is way overkill, too much work, and shows that you don't trust the membrane system.

    To your question about airspace behind shower wall, several years ago on this forum someone suggested putting thin lath strips between the drywall and the OSB SIP skin, just to create a vapor-open assembly that will mitigate against unforeseen (or unseen) water damage. It's the ol' belt-and-suspenders.

  6. Expert Member


    The location of the membrane depends on what system you decide to use build the shower.

    Schluter depends on the membrane as its waterproofing and you tile directly onto it, so you can use a variety of backers including regular and coated gypsum board, and cement based substrates.

    Coated gypsum-based substrates like Dense-shield are also both the waterproofing and tile-backer, so if you were going to include a membrane as further insurance it would go behind the Dense-shield.

    It is also common to use cement board as a tile substrate, and the membrane would go behind it too.

    In each case it is important to integrate the bottom of the membrane into the shower pan or drainage.

  7. Expert Member

    No, not with Schluter. I was listing three options most people use.

    The most common shower assembly is still probably cement board over a vapour barrier or building paper. I'd substitute a membrane like Grace I&W for the VB if it was going directly onto the OSB SIPs skin.

    As you say DensShield is weak at the seams, so a membrane as a backer behind it in these circumstances is a good idea too.

    Edit: I don't see much point in using a cement board behind a Shluter membrane. It's virtues are negated by being behind the waterproofing. I'd use something that held screws better and was easier to work with like green board - or DensShield.

  8. user-3368124 | | #8

    Thank you for the feedback. My biggest concern is the air space / membrane. I can pull a design from these comments, thanks. H

  9. user-2310254 | | #9


    I did not see an option for placing the backing material in front of the Schluter membrane or panel. If you were using the panel, I suppose it could be applied to the studs. But I would advise Howard to check with the company's support line for further guidance.

    DensShield is a backer plus moisture barrier product, but I think you must be careful about sealing all penetrations (which is the case with Schulter as well).

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