Capillary break between footing and stem walls, how important is vapor barrier?
qofmiwok
| Posted in General Questions on
Job is paused while we figure out what to do…
How important is it for this barrier to be vapor permeable as opposed to waterproof? The Protecto LMW200 is often recommended and it is vapor permeable (not super high but 10’ish.) My architect can’t figure out why vapor permeability would matter. The Building Science Inc article on this says it should be a vapor barrier, but they show products which are not vapor barriers.
Also, should the capillary break cover the whole top of the footing or just where the stemwall is? BSI’s article shows the whole thing.
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Replies
The idea is to prevent moisture wicking into the stem walls. So sure, vapour closed is ideal, but if I were in a pinch, I imagine a low perm coating would still do a good job and significantly reduce the stem wall from absorbing moisture moisture absorption.
Covering just the stem wall area is fine. But consider how integrating the stem wall damproofing and water management system to the footing will be done. It might be easier from a work standpoint to cover the entire footing when you have easy access to it, than when the walls are in place. It depends on your site.
Jamie
Thanks Jamie. We will be using a membrane down the exterior foundation wall and footing. They just hadn't ever done a break between the footing and walls like I requested, and they put the rebar in first which would have made it too hard to install a membrane.
They actually used Drylok Extreme which I understand builders use, but the mfr says isn't approved for that purpose. They receommeded their Drylok Floor and Wall, but only after 30 days of cure and ours was done after only a few days of cure. I have no idea if it will work as is, or if we should cover it with one actually recommended for this purpose like Protecto LMW200. (Or to be honest we might sandblast it off because it has chemical fungicides which they weren't supposed to use.)