Drywall directly on stem wall
tomk358
| Posted in General Questions on
I’ve got a 1′ tall stem wall in my current design for a house, the outside of the stem wall is insulated with 6″ of XPS and will have a moisture barrier on the stem wall. The slab has 3″ XPS underneath.
I’m wondering if I should build the walls flush with the inside edge of the stem wall, and then run the drywall all the way down over the stem wall- attaching with glue?
Or is it better to make the drywall end at the stem wall and paint that last 1′ of concrete, in case of moisture?
Thanks,
-Tom
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Replies
Don't glue the drywall flat to the concrete- that provides a powerful capillary path for moisture to get into the gypsum. Instead, put 1x furring at a standard stud spacing to the concrete, and hang the drywall on the furring. The air gap provides a powerful capillary break, and even the furring can dry into it. As long as you don't use any thing more vapor retardent than standard latex paint on the drywall, the concrete and air-gaps can still dry toward the interior.
Leaving a 1-3" gap between the slab and both the bottom edge of the furring & gypsum keeps it from wicking any potential moisture upward. Then use exterior grade fiber-cement or PVC trim board for the kick boards at the bottom of the finish wall.
Thanks Dana. That's what I'd feared.
Is painting the concrete a viable alternative solution?
I'm trying to avoid furring if possible- due to the already complex nature of my larsen truss wall design, and it also seems like I'd have to use 2x6 on the wall instead of 2x4 if I have the wood wall overhang the stem wall to make the furred drywall flush.
Or maybe I could use a tall PVC trim board for the kick, and that would cover the stem wall? I guess it's really only 8" on the inside...
Tom, Any chance you could post a wall section? A solution might become apparent if we could see exactly what you are facing.
Here's a drawing that should help explain. So far my ideas are either
1) fur out from the stem wall
2) finish and paint the concrete on the stem wall
3) cover with pvc trim
Oops, forgot the attachment.
Thanks Tom. Can you explain why you incorporated the stem wall or why the slab isn't at the same height as the wall? You probably have good reasons for them but it is a variant of slab on grade I haven't seen before.
I'm severely limited in height by local bulding codes, and live in a very very wet climate, so I'm both trying to maximize ceiling heights, and also not build below grade so I don't have to deal with moisture problems.
Earlier I had a sunken floor to get more ceiling height but have since abandoned that idea.
Tom,
The easiest solution is just to fur everything on the interior side before the drywall goes up. Run your furring strips vertically, on top of the concrete and in line with the studs, and extend the furring strips from the floor to the ceiling. Shim as necessary to make sure that the furring strips are co-planar, and then install your drywall.
Since it's only a foot high, I'd make the bottom plate overhang by 3/4" and attach a 1"x3" to the stem wall at the slab to act as a nailer for the drywall and trim.
Malcolm,
I understood that Tom doesn't want to overhang the plate on the interior side. He wrote, "I'm trying to avoid furring if possible- ... it also seems like I'd have to use 2x6 on the wall instead of 2x4 if I have the wood wall overhang the stem wall to make the furred drywall flush."
Martin, you are probably right. I was going off the details he posted which seem to show he could move in the 2"x4" wall with no consequences.
Thanks again for all your help. I've decided to go for a building variance on the height, which would make this a moot point- but if that fails, I'll do the full length furing strips as Martin suggests.
This website is such an amazing resource, I really appreciate it.