Vapor Barrier Detailing for Concrete Slab
So I’m preparing to pour a concrete slab on grade in part of a daylight basement. I’ve finished the excavating and placed and compacted the base. I’m further along than the picture shows. I’m wondering how people typically finish the vapor barrier along the wall or top of footing prior to pouring concrete. I’ve seen details where people leave excess vapor barrier up the wall and then trim it after the concrete is poured, but a friend recommends taping it just below the top of the finished concrete slab. I can see the advantage of this since my snapped lines for the top of slab elevations won’t be covered up by the vapor barrier. I’m wondering if you guys have any advice? What kind of tape to use? I’m weary of investing in Stegotape since I’d really only need about 80 linear feet. Maybe just duck tape? I have swellstop all around, so it only has to survive the pour, right? Thanks in advance!
A little background. The slab is going in kind of a strange space directly beneath my single car garage that daylights to the backyard. The garage is on a suspended slab above it. For whatever reason, the original builder and subsequent owner never poured a slab in the space despite having it mostly excavated. It has concrete walls all around except for the daylighting wall which was wood framing. Needless to say, the framing of the daylighting wall was pretty distressed from all the moisture in there for 40 years, so I reframed it with a garage door rather than replacing everything. The room is 10’x28′.
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Keep in mind that whatever you do the vapor barrier won't be "perfect". Someone will punch holes it while pouring concrete, or the tape will be torn loose along an edge. And even if the plastic is perfectly applied, some mosture will seep through, and more moisture will do an "end run" around it.
What you're after is "pretty good" -- no need to lose sleep over it.
A vapor barrier that is 99% intact
is 99% effective.
I would tape the VB to the wall below the snap line with whatever tape will stick. Another option might be something out of a caulk tube, like acoustical sealant. I've heard of folks using the Tremco brand to stick VB to itself and to concrete.
He's got (old) masonry walls. Moisture will come through those regardless.
His post
says he has concrete walls, I see nothing about masonry. My suggestion is that the VB protect the bottom and the edges of the slab, that's really about all you can do.
Concrete and masonry are essentially the same thing. (Yes, technically poured concrete isn't "masonry", but whether poured or block the walls will let moisture through.) And my suggestion was the same as your last one -- simply do the best you can and not worry about it. It doesn't have to be perfect.
I have not found a tape to stick to concrete ,I have even tried ice and water in the summertime
Stucco tape
There is a masking tape made expressly for stucco, that sticks well to concrete.
Nailing it up with the expansion joint
I'd just put it against the wall, and put the expansion felt over that, and then nail the felt to the wall.