Andy Engel Basement Floor Insulation with cork flooring
There are numerous threads about Andy Engel’s famous article on the stay-dry no mold basement flooring approach (XPS covered by plywood). I have a couple questions that I cannot find answers to
1) Some sources seem to suggest completely blocking moisture (for example, discussions on green building advisor and building science corporation websites) while Andy’s advice is to allow some drying to the interior. Allowing some drying makes sense to me but I would appreciate guidance and to hear how various approaches are holding up over time.
2) Should I put a vapor barrier under the XPS if the concrete slab stays dry? It has an epoxy coating already but I can add a layer of plastic or dimple sheet.
3) We would like to install cork flooring over the plywood but I have not been able to find permeability ratings for cork flooring products. It seems that the flooring should be at least as permeable as the XPS and plywood (perm ratings below 1 but still more permeable than a barrier or than vinyl flooring)
Thanks Much
Doug
Replies
If the floor has been reliably dry I can't see a problem with your plan. I think the XPS offers a good balance between controlling moisture without trapping it. The cork itself is breathable but the type of adhesive could be an issue.
I just put in a glue down cork tile floor and then put 4 coats of urethane on it, as directed by the manufacturer. Pretty sure that reduced the permeability of the cork.
Wow! That article has legs.
There's not a lot of consensus on some of these issues. The trouble with a VB is that it can trap even small amounts of moisture, which over time become big amounts of moisture and then you end up with a puddle of moldy water. The flip side is, if the VB is complete and the slime is on the outside, then who cares? The truth is that every basement is different and approaches can be tweaked. For example, we did a basement this summer where there were height issues and we couldn't insulate the floor. Instead, we put down a VB and ran LVP flooring over that.
Particularly if house is relatively new, say the past 30 years, odds are there's already plastic below the slab. I wouldn't worry a lot. I think another VB on the floor is not likely to cause any trouble.
Thanks All! Andy - maybe time for an updated version of the article! It is the best source I have seen for dealing with a common issue. We tore out the old drywall and stud walls which were put up with fiberglass insulation; not surprisingly there was mold where the studs met the concrete. We would be better off if everyone had a copy of your article.
A further question. Some of the comments suggest the option of a floating floor (two layers of plywood glued and screwed together but not screwed to the concrete). Has anyone tried it with success?
On the cork, has anyone seen perm ratings for various brands and products? I think they claim some breathability if you rely on the factory surface treatment but I cannot find specifics. This should be a low-wear location; no kids, dogs or heavy equipment. For the glue, I am guessing that the glue is permeable as long as it does not cover 100% of the surface, but guidance would be appreciated.
Thanks again
Doug
People have done floating floors as you describe. Code would require the bottom layer, in direct contact with concrete, to be treated. I'd definitely want a VB under it.
Also, thanks for the good words!