Retrofit concrete vapor barrier – shop floor
New Orleans, LA – Climate Zone 2
I have a shed/shop approximately 16′ x 20′ – I’m looking for the easiest method to reduce condensation of the concrete floor slab. Either pour on top or a system approach with new plywood walk surface.
The slab is not continuous – it appears to be added on to with formed joints. I will need to grind some high spots due to settlement. I do not know how much differential there is, but assuming its inches a concrete topper seems appropriate.
[Option 1] Vapor barrier plus thin concrete topper
– What can I use a barrier under a thin topping mix?
– What off the shelf bag products would be best up to 1-2″ as a finish floor?
[Option 2] Built-up assembly, floating floor (not repouring)
– Grind/fill joints and spot self-leveler > vapor barrier (taped) and mechanically fastened plywood subfloor
or
-1/2″ XPS foam board (taped), plywood subfloor adhesively bonded, true floating plank floor.
I’ve looked at fluid applied membranes such as TEC LiquiDam EZ which I’m not opposed to.
TEC® LiquiDam™ Product Overview Video – Bing video
Its just a shop at the end of the day, but with all the moisture, storing tools and materials in there now may as well go straight to the dump…what’s the easiest and most cost effective way to control moisture rising?
Thank you.
Replies
You could consider something like this:
https://www.lowes.com/pd/Delta-328-sq-ft-Standard-0-3125-in-Flooring-Underlayment/999919440
and top with some tongue and groove subfloor, or just some floating flooring of your choice.
But if the slabs are not stable, you might want to lay down some sleepers and then the new flooring.
Thank you for your response. Delta makes great products - I'll have to do a bit more research. At $0.60 / sf that seems hard to beat and I know several of their products are straight ground contact. Thanks again,
I had a similar issue in my basement. Slab had no insulation under and was a huge heat loss. I went with [choice 2] using floor leveler then PT full 1" x 2" sleepers @ 16" cc then cut 1" styrofoam to fit snug between sleepers. I anchored the sleepers occasionally as needed with masonry anchors but is mostly floating. The vapor barrier goes on top (the warm side) then a plywood sheathing and flooring of choice. It made such a comfortable and warmer floor. Its been down for 15 years now and I have no regrets.
Thank you for your response. I suppose being inside the conditioned envelope you didn't have much issue with condensation (drying to the inside). I think if I do go the route of sleepers I may drop some sill sealer foam underneath. This is all outside, unconditioned - condensation on the slab is primary issue. I'll need to improve the ventilation in the shop for sure. Any lingering smell issues?
Thank you
No smell. I had to lift a section a few years ago during another reno and everything was dry and sound. Condensation is certainly a challenge if its unheated. I think I'd increase the insulation and ventilation as you already suggested. Best of luck.
Nelson