Solving for Uneven Sill Plate
Hey all,
My addition has uneven sheathing to foundation across all three walls. Some sheathing is proud of the foundation and some areas the foundation is proud of the sheathing. Not major, but definitely not uniform. So now I have an issue of my z bar flashing running flat for Hardie plank. That’s a super problem to have. Just fantastic. Dang it. I assume I should correct by attaching sheathing to get it uniform (ie, sheathing proud of foundation, because I can’t correct where it is already like this?)
It’s a vented crawl space foundation, but I intent to encapsulate and don’t care about detailing to work around the vents.
I assume from all my reading here I do want to weather tight the foundation, sill, and sheathing together. I bought Prosoco Joint & Seam (perm 19 at 20 mils). My idea was originally to Prosoco 2 inches of the foundation, exposed sill, and 2 inches of sheathing. Z bar covering the non show/uv protected prosoco.
Then I got a wild idea and spent a fortune on 6″ Siga Fentrim tape (1.7 perm). I had the idea to put that tape over the Prosoco (should be compatible just fine) with the tape extending past the Prosoco on the foundation.
Terrible idea? Trying to understand where perm rating comes into play, because I know the foundation does need to dry at the top plate somewhere…
Thank you very much!
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Replies
@Ryan_SLC I believe you and I are attempting to do the same thing here. Or very similar at least. I am putting together some photos of my work so far with the sill plate transition area (exterior where sheathing meeting the foundation). I too have similar questions related to where how to apply the liquid flashing vs. Siga Fentrim vs. existing Tyvek.
@Ryan_SLC - do you have any pictures you could post here?
Ha, because my title was so changed from what I posted it as, I had no idea this went with attention.
I prosoco'd the area 4". Next I attached ripped plywood pieces onto the sill where the sheathing was short of the foundation. Then I attached the 6" Siga Fentrim to the sheathing and 2 inches to the foundation. This allowed the Siga to be pretty flat. I was not terribly impressed with Siga tape here knowing I bought it for the foundation attachement. It didn't seem to be more sticky than the three other tapes I was using; Benjamin Obdyke UV+, 3M weather flashing, and Zip. So far, I think the Odbyke tape has stuck hardest and is substantial.
I put the Z bar as far down as I could on the ripped plywood strips. It might not be solid, but my non trade fix is certainly better looking than what I was left with.
This crappy transitioning is leading me to think about doing a water table trim, but I am conflicted because the Hardie Plank should lap down enough.
Ryan_SLC,
Details that rely on the foundation and framing above being co-planar - exterior insulation that extends down continuously, strapping or flashing, etc - are asking for trouble.
I hear ya. That's why I asked.
Sheathing on the three new walls either extended beyond the foundation, was behind it, or was co-planar.
Since I can't change either the sheathing or the foundation, bring it all to co-planar seemed like the only fix.
I am hopeful that prosoco liquid joint filler + Siga + z bar +house wrap is sufficient...but I did ask because it truly is a mess...
haha Malcom, you rascal. I got the idea of shimming out based on the following:
https://www.greenbuildingadvisor.com/question/sheathing-flush-with-foundation-or-overlap