Sill plate and rim joist question - DIY Chatroom

bhasty · 10-12-2009, 05:21 PM

Hey All-

Wondering if someone can help me identify something. I'm getting ready to replace the shoddy batt insulation around the sill plate in our unvented crawl space with foam board, caulk and expanding foam. But I've discovered that there is some kraft paper running between the sill plate and the rim joists. Does anyone know what this is for? It hangs over the top of the foundation wall.

I don't think it's a termite barrier, or capillary break. Is it supposed to hold the batt insulation in place? And how do I work around it when installing the foam board on the rim joist and sill plate? It won't be very air tight if I leave the paper hanging out.

Thanks much for any insight!

See the attached pictures if that helps.
House is 20 years old in the land of WI.

bhasty · 10-14-2009, 04:09 PM

No one has any idea on this?

Or is this just a bonehead beginner question?

Thanks in advance!

Maintenance 6 · 10-15-2009, 08:48 AM

If it's just plain craft paper, it's not doing anything. Tear it off. Guys used to put tar paper between the sill plate and the masonry to stop moisture (before sill sealer and treated lumber sills) from wicking into the wood. I have no idea what plain craft paper would do between the sill and rim joist.

bhasty · 10-15-2009, 04:07 PM

Well, after closer inspection, I see that it's not just regular kraft paper. It's got two layers of paper with some wax or tar substance in-between. And it's installed between the sill plates and joists, not between the plate and masonry.

Still okay to remove the excess? I would think leaving it there would just provide another surface for mold to rest.