Capillary Break for Pier-and-Beam Foundation
I have been reading a lot of material on conditioned crawlspaces and foundation waterproofing from this site and BSC. However the discussion seems to focus on foundations with a footing. What about foundations with piers that go 15, 20 feet or more into the ground and have no footing. How are capillary breaks applied to all the piers in the foundation? I have seen a mention about waterproofing the tops of all piers and having the vapor barrier lap above the bottom of the waterproofing material. Is this the way to do it? Is there any issue with the water travelling up the piers not having any way to escape other than falling back down? Any better approaches?
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I will give your post a bump.
The purpose of the capillary break on top of a foundation, or a pier, has nothing to do with the masonry itself -- the capillary break's function is to protect the WOOD members (or steel) that lie on top of the masonry and use the masonry for support. It doesn't matter if concrete stays wet, but wet wood is prone to rot and insect damage.
How you would add a capillary break to a pier depends on how your structure is assembled. If you have a steel bracket with embedded bolts on the pier, a capillary break probably isn't necessary. You need a capillary break if you have wood members resting directly on concrete, or if you have steel resting directly on concrete. In the case of a regular foundation, a sill sealer gasket is usually sufficient to also work as a capillary break. If you are retrofitting something later, I prefer HDPE sheet since it's fairly stiff and slick and relatively easy to slide into place. I wouldn't trust a typical vapor barrier sheet as a capillary break since it's too easy to damage when moving things around. Rigid HDPE sheet of 1/32" or more thickness is far more durable.
Thanks for the insight Bill. The target of my question is more surrounding the role of a capillary break placed between the footing and the foundation wall. As I understand this will prevent water from coming up through the masonry and into the enclosed crawlspace, thereby decreasing humidity levels. However when building with piers, there is no footing and so no place to put this capillary break. The only alternative I had seen was described at JLCOnline by Todd Usher of Addison Homes out of South Carolina. Their practice is to apply waterproofing to all the piers on top and down the sides so that the vapor barrier will lap over the waterproofing. How necessary is something like that? Does anybody try to manage this in another way?
Sorry about that, I'd thought you were asking about the capillary break between the masonry and wooden parts of the structure. That's usually what gets asked about.
You're basically correct that the capillary break at the footing is there to keep water from wicking up the foundation wall. I'm not sure how you'd implement something like this with a pier, but due to the lower total surface area of the piers I'm inclined to think the need for that capillary break at the base is much less. Basically I don't think it's a huge problem if you don't have a capillary break in a pier structure, except at the top, but I've only ever worked with piers outdoors to support large industrial equipment where it's not an issue at all. I'll be interested to see if some others comment on this who have more experience with this particular type of structure.
Capillary breaks between the footing and walls are still incredibly rare as a standard practice. That's not to say they aren't good idea, but given their use in well performing houses is very limited, I'd say they probably fall in the category of an improvement that may or may not be necessary.
Given that the amount of moisture that can rise thr0ugh capillary action is largely a function of the am0unt of concrete that is exposed to both the damp sub-soils and the crawlspace, pier foundations are probably the least likely to benefit from a break..