What to do with the bottom of the Tyvek with a slab on grade?
We’ve got a single story slab on grade, plywood sheathing, seams are taped with Siga Wigluv, including the bottom seam from the plywood to the top of the slab (using the dockskin primer). We’ve installed tyvek homewrap over the wood sheathing, and cap nailed all the red dots.
Now at the bottom, it just hangs all the way down to the ground over the slab, which is about 12″ above grade (final grade isn’t done yet). The lowest nail point is the red dots on the wood.
What are we supposed to do, if anything, on the bottom of the wrap? Should we trim it back to x” hanging over the slab? Should it be taped or caulked to the slab somehow? It seems like it should be left open at the bottom so any water that might get behind it can drain out instead of being trapped. Does it just hang loose and open down there?
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Lightnb,
There are two schools of thought, which are reflected in the installation instructions. Cut the Tyvek 3/4" below the level of the slab, then either leave it loose, or tape. The tape makes for a better air-seal, but means any water than makes it's way behind the house-wrap has no way of draining.
My own feeling is if there is enough water that it needs to drain, something major has gone wrong. However, in your situation there isn't much point trying to air-seal the WRB when you have done a good job with your sheathing.
As far as it "hanging loose and open", the bottom of the Tyvek is sandwiched between the sheathing and either the cladding, or the perforated base-flashing or Cor-a-vent, if there is a rain-screen.
Thanks Malcolm,
Does the siding (horizontal, wood) typically start about 3/4" down the slab as well? Is there any type of flashing strip or termination on the bottom of the siding? Or anything that protects the siding from direct contact with the cement? Does it make sense to install the siding, then trim the wrap to the bottom edge of the siding afterwards?