Methods for capillary break at foundation wall/sill plate ioint
I was curious what different methods there are to create a capillary break at the foundation wall and sill plate joint? A popular item seems to be the small pink foam roll, but there have been several comments that it is only good as an air barrier and not a moisture barrier. So if this isn’t good for that, what is the preferred choice? I haven’t really found a lot on this other than a plastic sheet or a gasket product. The gasket looks to be quite the novelty and somewhat expensive, so I’m not totally sold that this is what most are doing when creating the break. Not sure about the plastic sheet idea either. Is it something that comes in the right width roll? Or just your typical hardware store sheet cut to fit? Thanks in advance!
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Hi Jason,
In general, there isn't a lot of attention put into a capillary break at the sill. That's why sill plates are pressure-treated lumber. Sill seal and other products like the gasket that you mentioned are mainly used as an air seal, though they do help to create a capillary break. I've also heard from at least one builders who uses a peel-and-stick membrane on the bottom of plates, and I've seen the poly sheeting used in sealed crawl spaces and under slabs lapped up and under the sill. It can then be taped to the air barrier on the walls for a continuous air barrier. Here's an example of that approach: http://www.greenbuildingadvisor.com/question/methods-for-capillary-break-at-foundation-wall-sill-plate-joint
I guess If you were concerned with capillary action wetting framing you could also coat the top of the foundation wall with a fluid applied waterproofing.
Thanks Brian. Sounds like you're confirming what I'm seeing. I just know that when reading about the need to provide a capillary break, you also find articles where someone has had to jack their house up to replace rotted sills. I'd personally like to avoid that with our new house. I'm in the process of trying to get approval from our local inspector to provide one between the footer and foundation wall (fingers' crossed). I figured if I provided another at the sill, then (along with encapsulation) we should have a really dry crawlspace, sill, etc.
Also, I think you accidently linked to this question instead of the article you were intending. But I'd love to read it if you don't mind updating.
Sorry about that. Here's the right link: http://www.greenbuildingadvisor.com/article/air-sealed-mudsill-assembly
And keep in mind that preventing your sill from rotting is also about keeping rain and runoff away from the sill.
Thanks! And that's a good point. I'm just hoping to do things right up front.