Air sealing the sill plate

[mepstein]

I would like to water/air seal the sill plate to the block before I install the sheathing. I purchased 4” “Tite Seal” butyl flashing tape but it doesn’t stick well to the block. It’s older, has been parged with cement and seems to be too sandy for every butyl to stick. Should I paint with drylock paint to give it a better surface or is there a better process?

 

[Bogie1632]

Re: Air seeping the sill plate

Caulk it. Large gaps use filler rod (ok) or a gap filler expanding foam (better).

V/R
Bogie

 

[Raisedonadeere]

Re: Air seeping the sill plate

And you can do from inside unless you have baseboard or something blocking. you are not trying to fill the space under the sill plate, just cutting off the path of air into the building. Air space under the plate could be a good thing as long as it cannot get from outside to inside.

 

[egdinger]

Re: Air seeping the sill plate

I haven't used them on concrete, but perhaps one one the liquid flashing products like Zip's or prosoco fast flash?

 

[tonyciambrone]

Re: Air seeping the sill plate

I haven't used them on concrete, but perhaps one one the liquid flashing products like Zip's or prosoco fast flash?

Yeah buddy- prosoco R-guard

 

[Leaflessshadetree]

Re: Air seeping the sill plate

I put in sill sealer before I stand the walls up. Depending on your situation (building size etc) it may be possible to lift the walls and slip it in.

 

[mepstein]

Re: Air seeping the sill plate

I purchased some Siga Wigluv tape and primer. Not cheap but supposed to do the job.

 

[nadogail]

Re: Air seeping the sill plate

I'm partial to foam backer rod and silicone caulk, before the sill plate is fastened down.

 

[ItsNemo]

Up here they always put sill gasket between the foundation and bottom plate.

 

[PugetDude]

Big Stretch caulk; use foam backer rod if the gap is larger than ~1/4-3/8"

 

[mepstein]

Thanks for all your ideas. I’ll do the outside first and then caulk and seal the inside.

 

[James-W]

Up here they always put sill gasket between the foundation and bottom plate.

That is what I did with the garage when I built it.

 

[iced98lx]

suggestions of a fluid applied product like Prosoco R-Guard are spot on, I'd do it even if you had a sill gasket in there.

I wouldn't personally do the inside on a garage just to give a drying path but if you do go for the inside and outside make sure the outside is well done.

 

[Raisedonadeere]

suggestions of a fluid applied product like Prosoco R-Guard are spot on, I'd do it even if you had a sill gasket in there.

I wouldn't personally do the inside on a garage just to give a drying path but if you do go for the inside and outside make sure the outside is well done.

I would definitely not try to get a seal on both sides. Outside to keep water and air out or if that can’t be done then inside to keep air out of interior space.

I have seen lots of wood rotted from being sealed so enclosed that it couldn’t air out from condensation, wicking etc.

 

[67CarGuy]

Agreed on not sealing both sides - provide a drying path. The fluid applied barriers are used in larger residential and some commercial projects for a reason, because they work well when installed correctly.

If the sill is already down, then foam or caulk + backer rod is the easy way to go.

 

[maxpat82]

I used elastomeric scellant on the inside (cold climate here)

 

[Kaizen]

Re: Air seeping the sill plate

I haven't used them on concrete, but perhaps one one the liquid flashing products like Zip's or prosoco fast flash?

+1. More expensive but definitely better then normal caulk. Go heavy.


Sent from my iPhone using Garage Journal

 

[acer66]

I would try to seal on the outside since that is
your first line of defense and if you get water on the inside you know you got a problem.
If you seal it inside you could have problems covered up besides it keeps bugs out.

Like mentioned before I also would look into liquid flashing.

 

[tjansson]

I just built a new wall for my garage. I put a bead of acoustical sealant on the foundation, then sill foam, then another bead of acoustic sealant, then the PT sill plate. After the wall was built, I used Zip liquid flash lapped 2" onto the foundation, in the seam with the sill plate, and over the sheathing up 2-3". My objective with the liquid flash was more to prevent rot from splash back then air seal, though it will accomplish that as well.

The Siga tape seems like a good option. The liguid flash was slow and messy.

 

[ssdave]

I staple asphalt shingles, upside down, over the gap, with the edge of the shingle exactly on the bottom of sheathing line, typically 2 inches below the sill plate. Caulk first, or use a bead of roofing tar right on the concrete/sill plate gap.