Sealing sill plates to a slab
I have an older home on a slab in central Michigan. The sill plates under several of the walls have rotted and I need to replace them. I am totally gutting all these rooms for new floors and new dry wall., so every thing will be exposed. I’m planning on supporting the ceiling rafters with posts and jacks so I can cut out the old sill plates. I’m going to sister new 2×4 studs from top to bottom of the wall to the new sill plates. Since I will have only about enough room to slide the old rotted sill platges out and slide the new sill plates in, what can I use to seal the new sill plates? Also someone told me I cant use pressure treated wood for the new sill plates. Is this true?
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Replies
Here is one approach you can use this seal the sill plate:
http://www.conservationtechnology.com/building_gaskets.html
You staple the gasket to the plate and then install it on the foundation. The gasket also serves as a moisture barrier, so whether you use or don't use of pressure treated lumber isn't an issue.
Code requirements vary significantly from jurisdiction to jurisdiction. It is always best to seek out your local official for clarification.
The issues around pressure treated lumber is a change in the treatment chemicals. Make sure to use borate treated lumber for the sill plates. The outdoor rated treated lumber can corrode fasteners.
If you can fit a sill gasket make sure to use polyurethane caulking -it sticks to concrete well - look in the concrete isle at the big box stores.
> what can I use to seal the new sill plates?
Primer plus Siga Wigluv tape. I wouldn't expect as good results from caulk, even if you understand the importance of bond breakers, backing rod, adhesion strength and high ASTM C 719 movement capability.
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/review-siga-wigluv-air-sealing-tape
Al,
As Steve said: the first person to talk to is your building inspector. I've never heard of PT wood not being allowed as sill plates. ACQ treatment is corrosive, but that just means using galvanized fasteners, something you should probably plan on whatever wood you choose. Around here most lumberyards now stock MPS treated wood, which doesn't affect fasteners or contain arsenic.
Al,
Sill plates on concrete are usually pressure-treated. The reason your old sill plates rotted is because the builder made a mistake and didn't use pressure-treated lumber. So this time, use pressure-treated lumber.