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Community and Q&A

Can I place foam insulation over linoleum tile in a basement floor?

John Sullivan | Posted in GBA Pro Help on

I’m attempting to remodel a basement that is conditioned space in climate zone 4A (MD).

What I’m working with: The house was built in 1957 and has an uninsulated slab. It has tall ceilings, more than 8 ft. The previous owners placed vinyl tile over the original linoleum tile. The original tile was laid with a black mastic. The basement appears dry. We seem some efflorescence on the cinder block walls, but the basement is not damp other than humidity. The area I want to remodel has been finished space since the house was built, other than the floor. The walls and ceilings have drywall over furring strips. The basement does smell musty, but it it is very mild by most standards. The space is connected to a garage. All the perimeter walls are underground by about five feet with four feet of above ground space. I really only want to do one room. The basement has been framed in to created several rooms.

To breathe or not to breathe, that is the question.

All I have read says its fine to place foam on a slab followed by plywood subflooring. Some say its okay to go over existing tile. But is it okay to go over linoleum? What about the vinyl. Leave it or tear it out, since it does not breath at all. I would prefer not to remove any of the existing floor as it’s in good shape, and I want to avoid removing the linoleum tiles which may contain asbestos, or the the mastic , which might as well. I have two small children. However, I’m concerned about trapping moisture in a tile made of organic material that may create mold. Although manufacturers suggest linoleum has anti-bacterial properties.

I thought of removing the vinyl, which comes up with some exertion, and then placing a dimpled barrier followed by foam and plywood. This is based on this article.

http://buildingscience.com/documents/insights/bsi-003-concrete-floor-problems

Or just foam and plywood. If I use foam and leave the linoleum, do I need to go with a more permeable foam board, to allow better drying, or less permeable.

Any thoughts on what the best way to insulate and floor a basement with a slab covered in linoleum and vinyl.

Any help would be greatly appreciated.

John Sullivan

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    John,
    You don't want your floor to breathe. The soil under you concrete is damp. You want the moisture in your slab to stay where it is -- not evaporate into your basement.

    So go right ahead and install rigid foam on top of the linoleum and vinyl flooring. If you have any doubts about whether the flooring is a decent vapor barrier, you can even install a polyethylene vapor barrier under the rigid foam, just to make sure that no water vapor enters your basement by this route.

  2. John Sullivan | | #2

    I've added a photo that shows what appears to be condensation buildup under a tile. This tile is in a lower spot in the basement. I see some oozing about once per month and when i pull the tile this is what I see. Does this seem like a standard amount of condensate for a rather large 400 sq foot room. I don't see it when i pull other tiles farther away. Does this alter your answer in any way.

    John

  3. Michael D | | #3

    While you are there you may want to consider testing the tile and black mastic for asbestos. The odds are not low that one or both of the two has asbestos and if so getting them safely removed is a good idea, although not cheap. SInce you are disturbing it with your remodel its worth knowing for your own safety.

  4. John Sullivan | | #4

    Michael thanks for your reply. My intention is to NOT disturb the tile. But of course I'm worried about trapped moisture creating mold beneath whatever I place on top. Most of what Ive read calls for simply placing rigid foam insulation over concrete floors, and favors this technique because it does allow for some inside drying, although at a very slow rate. Vinyl tile is like placing a vapor or air barrier on the slab, which would prevent drying to the inside. I guess if the slab is always going to be wet, which most are all year round, it makes sense to prevent all drying to the inside. Otherwise you'd have moisture entering the basement at a constant rate. I guess the real questions is does anyone see any potential problems with using a vapor barrier over these two existing tile systems, or do i need to remove them to prevent mold etc.

    John

  5. John Sullivan | | #5

    I just saw this article https://www.greenbuildingadvisor.com/blogs/dept/musings/joe-lstiburek-discusses-basement-insulation-and-vapor-retarders

    Which seems to answer much of my question, and supports Martin's response. Now I need to figure out if I have enough external drying at the top of the foundation wall to insulate my walls. Also I need to see how the slab insulation and wall insulation should be sealed and positioned. Thanks again.

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