Shrinkage Cracks in ICF Walls
steve41
| Posted in General Questions on
Should I be at all concerned about these shrinkage cracks on the top of my ICF stem walls? There are 6-8 similar cracks, maybe ~1/16 wide.
It seemed like a very wet mix, and the cracks occurred very soon after pouring. I did keep water on the wall for a week or two. My gut tells me this is a non issue, but I did want to get a second opinion before raising the walls.
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I would GUESS that these small shrinkage cracks are not critical to the structure, but hard to tell without seeing the actual wall face.
Is this ICF wall in ground or above ground? Crawl space or full basement? How are the walls laterally supported? What was the reinforcement detail? Any openings in the walls?
Thanks plumb_bob.
Quick summary:
*It's a short stem wall on bedrock.
*The bedrock surface varies such that there would be maybe 6-30" of foundation below grade. ~12" above grade.
*The interior will be filled for a raised "slab" (concrete free). So lateral support is the fill on both sides. The only unbalanced fill will be the top ~12", which will be light aggregate (Glavel)
*no wall openings
*Reinforcement: #5 vertical rebar pinned to ledge every 18-24", extending through full wall. #4 horizontal rebar (2) per ICF, staggered
My two concerns are 1. the likelihood of further propagation and 2. air leakage. I believe my sill detailing will elevate the air leakage concerns. I think I'm all set, but this is my first foundation pour, so better to ask the experts. I don't have a sense for "oh, that's completely normal" or whether it's something to really be concerned about. Thanks.
Steve
Steve, that is normal for concrete that is too wet when it's placed and/or that dries too quickly. A nice thing about ICFs is that they tend to allow concrete to cure slowly. The cracks are almost certainly only at the top, possibly only in the cream layer, and should not pose a major problem--especially not with your reinforcement schedule.
I disagree with Plumb Bob and others who say that concrete always cracks; it doesn't, but if you have any concerns I agree with his advice to have an engineer look at it.
All concrete will crack sooner or later, period. Vertical hairline shrinkage cracks are not typically an issue structurally.
I think your foundation will be just fine, it is very well laterally supported and properly reinforced. If you have serious concerns you could have an engineer out to give an opinion.
If you are filling the foundation and having a "slab" type floor, then detailing the air barrier from the slab to your wall plates should not be a problem, and air leakage through the foundation walls will not be an issue.
Thanks once again Michael and plumb_bob. Great feedback as usual.
I think I'll map out the crack areas for future reference. I may even add a few inspection holes through the exterior EPS foam of the ICFs that I can replug- to inspect crack depth/severity/ future propagation. I would just need to make the exterior ICF protective cover easy to remove.
I know there are some good injectable epoxies for crack filling, but I don't know if they are structural or if they would melt the EPS if the cracks extend that far. I haven't done the research but if anyone has any suggestions it would be appreciated. It would be nice to have an option in my back pocket.
I've seen the same on ICF walls. I believe it is normal shrinkage. The concrete shrinkage gaps I have seen on top if ICF walls is around 1/16 at the widest.