Manufactured foundation drains, e.g. Z-Drain
Our builder wants to install the foundation drain on top of the footer instead of alongside of it. We complained that this would potentially give us a line of standing water above the footer/foundation wall joint (though it would remain some inches below the basement slab level. ) We will have Tremco Tuff n Dri waterproofing all along the wall and along that joint, so if it does a perfect job indefinitely then we should be fine. But if not, we could get some wicking up that wall. We’re going to the trouble/expense of installing a capillary break between footer and wall, but then we could have a wicking path into the wall starting from above that level if the exterior waterproofing was not perfect.
Since footers are normally poured in a trench around here, builder is warning that forming the footer with boards and installing a typical drain alongside of it would be costly and subs might balk. But he’s offering a less costly alternative: have the waterproofing contractor also install Tremco’s Drainstar Z-Drain, which would collect the water beside the footer. A 6″ slice of earth would have to be removed along the side of the footer and the Z-Drain slipped down into it, but footer could still be poured in a trench.
Anybody wish to share their experiences with this or similar products? Any additional considerations we’re missing? Or should we maybe just install a conventional drain on top of the footer and trust that the Tuff n Dri will be a near perfect water barrier along the footer/wall joint and above?
Thanks.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
William,
I think that you should tell your builder that the footing drain belongs beside the footing, not on top of the footing. If your builder asks why, tell him or her to read this article: How to Install a Foundation Drain.
-- Martin Holladay
William,
In any case, the DrainStar Z-Drain web site shows that this product, properly installed, should be placed beside the footing, not above the footing. So your worries are groundless.
.
Martin, I guess the idea is to slice away a bit of earth after pouring the footer in a trench as usual. Then the Z-drain would be folded and part of it slipped in that channel, so yes it would be draining alongside of the footer, not above it. We were told it would be less costly than digging further out provide space for the drain to run, and then forming up the footers with boards.
So it all sounds good, but thought I'd check here to see if folks like this product or not. One of my questions is about its strength and resistance to crushing.
William,
I wonder how forgiving the Z-Drain is to uneven footing sides? it looks to me to be designed to slide along a straight, even concrete surface. Footings poured in trenches are typically very irregular.
Uninformed speculation here, but I don't see why one couldn't put a drain under the footing (covered with pea gravel and with a small footer width increase). OK, maybe that creates an issue of the water getting to the drain.