Basement Laminate Flooring Underlay with Vapour Barrier
moose_head27
| Posted in General Questions on
Hi, I’m currently looking at some underlay for laminate flooring for my basement. Many products have a vapour barrier or require to use a vapour barrier underlayment.
Is a vapour barrier required? My house was built about 10 years ago. No idea if there was a vapour barrier installed below the slab. One section of the slab was blocked out from concrete for the shower rough-in and I do not feel any vapour barrier under the slab when i stick my hand under.
My slab is dry, no issues with moisture. I’ve also installed 1 inch XPS under plywood as a subfloor. Is there any concern with installing a vapour barrier underlay?
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Replies
Not sure on VB on top of foam idea......i did poly then foam.
FWIW.....my go to system on top of foam is 1/2 hardibacer sheets with 6 fasteners per sheet tapcons. That stuff is so heavy it does not move and probably only needs 2.
I have put thickest pergo laminate directly over 1"foam with success......but would now insist on hardi backer first.
The best place for a vapor barrier would be between the foam and plywood subfloor, but it sounds like it's too late for that. Moisture drive is from warm to cool, so on a basement floor, it is almost always from top to bottom. Most people think it's the other way. The risk of putting a VB underlay on top of the plywood subfloor is that, if there is a missing or defective VB under the slab, the space under the VB will eventually reach 100% MC and the plywood will rot. 1" XPS is a reasonably good vapor retarder by itself, as is concrete, actually. Unfortunately, laminate floors may or may not be a better VR than either the XPS or concrete, or both. If the seams of the XPS were taped, I'd skip the VB. If not, I would be tempted to use one of the really good European tapes on the plywood seams and still skip the VB.