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Community and Q&A

Perimeter slab insulation floor coverings

user-6828204 | Posted in General Questions on

We are looking at installing a gypcrete slab over 1.5″ XPS to be finished with a tile covering in a laundry room and engineered wood in the adjacent rec room. The rooms are below grade in a basement with no water intrusion issues (new foundation with excellent drainage). We are very wary of heat transfer around the perimeter as there is a wine cellar in an unconditioned room adjacent to the laundry room. We have been advised to put a perimeter of 2-3″+ of XPS around the perimeter of the gypcrete slab to prevent heat transfer.

My question: I understand a floating wood floor would simply go on top of the XPS perimeter, but how can tile be affixed to this perimeter in the laundry? Would we use a product like DITRA directly on the XPS edge attached with thinset?

Thank you

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, I urge you to change your user profile so that your name is displayed instead of "User-6828204." Here is a link to an article that explains the simple steps needed to do that: How the GBA Site Displays Readers’ Names.

    Concerning your floor tiles: It seems to me that the simplest solution is to install a layer of tongue-and-groove plywood over the gypcrete. Perhaps other GBA readers have another suggestion.

  2. Expert Member
    Dana Dorsett | | #2

    Using EPS instead of XPS is substantially greener, due to the fact that all XPS in north America is blown with extremely high global warming potential HFCs which leak out over a few decades, whereas EPS is blown with low-impact pentane, most of which is recovered at the manufacturing facility. This gives EPS stable long term performance, whereas XPS performance eventually falls to that of EPS of similar density.

  3. user-6828204 | | #3

    Hi Martin, I did change my name and screenname, but the forum software isn't picking up the change, I'm not sure why. Thank you for your response. Plywood is an option, but we would have to reduce the amount of insulation to make up for the additional build up. It would be an acceptable compromise given no other options. Thank you

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