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Community and Q&A

Slab Insulation Protection (Cement Board?)

idahobuild | Posted in Energy Efficiency and Durability on

Hello All,

Building a monolithic, slab-on-grade foundation with 2″ of rigid foam (XPS) around the perimeter.  In a video on the “Eco Home Network” channel, they use cement board to protect the XPS that would otherwise be exposed on the outside of the slab.  

https://youtu.be/qOcaZAi6Zsg?list=TLPQMjQwOTIwMjIpqAvj0qKSxA&t=18

I am wondering if anyone has experience with cement board for this use case and any thoughts on durability and getting a good finish on the cement board.

Any ideas?

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1
  2. user-5946022 | | #2

    If you are in an area where termites are a concern, you may wish to rethink rigid foam around your slab perimeter - it turns into a a termite superhighway...

  3. Expert Member
    KYLE WINSTON BENTLEY | | #3

    I've used cement board over insulation, and it takes cement based stuccos, which are essentially type s mortar, very well. It's pretty easy to apply after a practice run, and seems to be holding fine. I've used acrylic coatings after the stucco has cured, and it has shown to be durable so far. I would suggest using an expanded metal lath on corners, otherwise you'll have hairline cracking, even with the alkali resistant mesh tape that's often suggest.

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