Hello – Newbie here and was hoping for some guidance. I’m replacing my 2×8 sills and boxbeams with pressure treated wood. I would like to install a sill seal and bought the 5.5 in foam sealer. I laid it out so the seal is sitting on the outer edge of the sill (for air infiltration) going in 5.5 inches. Would that be enough? or do I need to add the other 2″?
Also, whats the word out there on any gaps between the boxbeam and sill. I’ve spent hours at HD trying to find square knot/chunk free lumber and found the lesser of the evils and planed them down as square as possible and I still have about a 1/8 gap in places where I can see light through. Can I just use a silicone caulk to fill the gap or should I use a construction adhesive?
Thanks for any input!
Replies
The 5" sill seal is
The 5" sill seal is adequate
For gaps, I use can spray foam
You do want to arrange the sill seal so that it largely prevents the wood from directly contacting the masonry. This cuts down on moisture tranfer from the masonry to the wood.
Sill seal is an air barier and does not one thing to prevent moisture movement. That is why PT is used for sills or another separation barrier to untreated wood is required
Don't agree with this
Sill seal serves as a capillary break, and I don't think it's a particularly good air barrier, although that's also one of its intended functions. EPDM rubber gaskets are better on both counts.
To the OP, I would install it full width. It won't take long to rip strips at 2" and lay them next to the full pieces.
Yes I agree that the sill seal is purely for air infiltration (and pretty poor at it). To be a moisture barrier it would have to be non porous. I was just wondering if the local inspector would bust chops on it not being the full 7.5 inches. I'm a homeowner and really cant afford to make a silly mistake like that, finish the job then have an inspector come in and say that it needs to be the full 7.5 inches.
Thanks for all the valuable input!
As far as inspection goes, in many areas sill seal is only required if treated lumber is not used. Right or wrong, that's the code here in MA. I think you're fine with the sill seal where you have it, but I would caulk the other side of the sill (interior it sounds like). And spray foam the gaps between the rim and the sill.