Basement baseplate
BG57Builder
| Posted in Green Building Techniques on
Just realized I used UC3B, which says for above ground, as my baseplate. Should I go back and use a green treated that is designed or designated for ground contact?
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Replies
BG57Builder,
What makes the biggest difference is using a sill-seal to ensure the bottom-plate doesn't take up moisture from the slab or stem-wall below. PT plates in contact with concrete can transmit moisture to the framing around them. Once isolated, it doesn't matter much what lumber you use.
Malcolm,
I follow the logic here, but in practice I've never actually seen anyone use anything but treated wood or redwood as a mudsill, and have always seen at least that pink sill gasket material between it and the top of foundation. Is it common in some areas to use a sill gasket + KD sill plate? (For context, I used to work in new England and now work in Montana.)
I ask because this recently came up on a job. The framer asked about the note on the structural drawings calling for treated or redwood mudsills, and said he never uses treated sills because he uses a sill gasket. I did some Googling and came across this article by JLC:
https://www.jlconline.com/how-to/framing/is-treated-wood-always-required-for-sills_o
The article makes it appear that the code language may be unclear on whether or not treated sills are technically required, but lands on it being cheap insurance & best practice to use both a sill seal / capillary break & treated material for the sill itself. Would be interested in anyone's thoughts/knowledge on this.
Paul,
Houses don't typically use PT lumber for sill-plates here in BC. I'm not against the practice, but was rather pointing out the necessity of a sill-seal, whether the the wood is PT or not.
Interesting, thanks Malcolm. I wonder if the splits are regional, or more local (ie, we do it this way here because we've always done it this way here and haven't had problems).
Also - I say I've always seen treated sill plates where I work, but my ancient house here in Montana has regular lumber on a rubble foundation with no capillary break in between. And of course, New England is similarly full of old houses with regular lumber plates directly on stone or concrete.
Paul,
It's always difficult to judge what drives these types of code differences that are unrelated to climate. Our code is revised regularly. That the requirement for PT sills hasn't been adopted says to me it isn't an issue - but I may well be wrong.
I also have a new concern that the "ground contact" green treated is possibly "too treated" to be used indoors. Is that a valid concern or no? Lot of chemicals in green treated and the ground contact ones have the most.
On new construction in New England I have never seen anything but a pressure-treated mudsill. But I have also been involved with hundreds of renovations to homes built before PT lumber was available, and most of those are still in decent shape, as long as the wood is somewhat rot-resistant such as hemlock, larch or white oak. I would not use the spruce framing lumber as a mudsill, with or without a sill sealer--condensation will rot it out in our climate. It might be ok in Montana, which is much drier, though just as cold so it would depend on the situation.
I have no concerns about using UCB3 in that location. I do recommend ground-contact rated for all exterior structures, though, whether in contact with the ground or not.
Is ground contact okay to use indoors for basement baseplate of framed walls? Or should that be strictly for outdoors? Worried about potential health risk or something of that nature.
The copper content is fine to have indoors. The other component is not as benign; whether you want to use it indoors would be up to you: https://en.wikipedia.org/wiki/Tebuconazole.