Capillary break – Footing to foundation wall
airfix
| Posted in General Questions on
If my foundation wall is poured while my footing is still green my concrete guy is telling me that the wall and footing will bond together during the curing process becoming one structure and thus a capillary break is not necessary.
This sounds plausible to me but what do those with experience say?
Steve
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Replies
Steve,
Your concrete guy is wrong. If the wall is poured on a different day from the footing, it's a cold joint.
More information here: "Capillary Breaks Above Footings."
Martin,
I actually sent that article to him to open up a dialogue about the topic.
Hopefully I'll get him to do a paint on capillary break as I have rebar protruding from the footing.
Thanks for sharing your knowledge.
Steve
Steve,
Even if your contractor was right and it somehow became a monolithic structure, how would that affect how water moved up through it and negate the need for a capillary break?
Malcolm,
Good point!
I bet the contractor is thinking “it won’t leak water”, the idea being concrete dams hold back water and they’re ok. Your contractor probably doesn’t understand that you’re taking about moisture wicking and dampness which is different from flowing water.
Bill
Oh i guess I misunderstood the capillary issue. I was thinking that the gap between the two concrete structures would be the concern. Then additional capillary action can happen between the foundation wall and the foundation wall insulation.
What you are saying is that because of the porosity of the concrete itself, capillary action happens within the concrete structure.
I that case Malcolm is correct. It wouldn't affect it.
Steve
Steve,
The concern about moisture making its way in between the two was dealt with in this article on Water-stops:
https://www.greenbuildingadvisor.com/article/petes-product-puzzle-cetco-rx-101-sika-703
I'm not sure how you deal with incorporating a water-stop and a capillary break at the same time.
Seems to me that a water break that spans the entire width of the wall would act as the capillary break too. The white color water break shown in the article, if installed the way I think it is, would basically be a plastic strip running the length and width of the base of the wall and should act as a capillarity break too.
Am I missing anything?
Bill,
If you look at the photo gallery accompanying the article, the water-stop is installed vertically. I'm not surprised you are confused. it's like nothing I've ever seen either.
I see what you mean. I think it was image 5 that showed it pretty clearly. I was thinking it was supposed to lay flat along the bottom of the wall section, right above the footing — the same way a capillary break would be installed. With the vertical orientation shown in the pic, a capillary break would certainly still be needed.
I do mostly commercial work and I’ve never seen this stuff. I design the electrical and mechanical systems though, so usually my concerns with the foundation is “is it done yet” and “make the slab thicker under the heavy chiller, generator, etc” :-)
I’ll have to to go read more about this stuff out of curiosity.
Bill
Won't a capillary break between the footing and foundation wall act as a waterstop anyway?
Steve,
No, a capillary break is not the same as a waterstop. In some cases, a capillary break is as simple as a coating (paint) or polyethylene. Neither approach is intended to stop water.
In a residential project, the traditional method for reducing hydrostatic pressure and preventing water entry is to include a footing drain surrounded by crushed stone -- in some cases supplemented by dimple mat. Unless the footing drain fails, this method works, and a waterstop isn't necessary.