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Exterior concrete stem wall wicking

Jamie_K | Posted in General Questions on

– Is this concrete wall wicking going to cause mold issues inside?
– If it is an issue, how do we stop the wicking – rake it up for first couple feet next to stem wall so gravel is looser, which should provide enough capillary break?

I believe this means it doesn’t have enough capillary break, but I don’t want to waste the money of removing all this new gravel if it’s not an issue. I believe it’s okay for concrete to dry to outside, so maybe if it doesn’t come through inside it is okay.

We have 3 ft eves here, and we are trying to get away without gutters so we don’t have to battle the high maintenance winter gutter issues, ice damming, etc. The red line is the bottom of the slab, which has a good perm commercial grade vapor barrier underneath. The grade is at least 5% grade away from house (e.g. 6″ in 10 ft). Slab is 5″ thick (but pic w/o measuring tape has wicked higher than that 2″ pic measurement). Inside we are going to epoxy floor and 2 ft stem wall, except bathroom portion we have furred out wall so we will spray with closed cell spray foam.

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  1. BrianPontolilo | | #1


    The only maintenance issue with gutters is cleaning out the leaves and there are products generally called gutter guards that you can install to keep the leaves out. Ice dams generally have nothing to do with whether you have gutters or not.

    I think you meant to attach some photos to your post. They would be helpful along with some information about these stem walls. Were they recently poured? Was there a vapor barrier installed? Are they insulated?

    You'll find a lot of info on foundations here, and may be able to determine if yours was installed properly:

    1. Jamie_K | | #3

      Yes, I keep trying to post pic's Brian...bummer, I wonder if I'm the only one who has problems posting pics. I've tried Safari and Chrome on Mac as well as iPhone. Do you know if others have issues posting pics - this happens to us often? If you have any tips, I can try to post them again as I think that would be way less confusing to see pics instead...but I'll try to explain below :)

      I believe we are okay with the normal type of ice dam issues from melt off, attic ventilation, IceShield, etc.; however, when it freezes up here in N Idaho / E Washington area (borderline 5 /6 climate zone) over winter, the gutters can create ice dams backing up into eaves from gutters. I've also read about this in one of Martin's articles in the comment section from his dialogue with many people. Heat tape may help I believe, but we also have 60 ft runs as this is a 40x60 shop...and it's hard to prevent leaks at the seam, so if we had to do gutters we would probably put piece of metal over gutter seam I guess vs. caulk as it always fails and leaks. We would like to get away without gutters, hence why we did 3 foot eves...but we have some water wicking up, bummer.

      I've read a lot about foundations before we had poured. I think it was done right but perhaps the crushed rock/gravel even though it's at least 5% in the grade away (e.g. 6" over 10 ft), in being tight against concrete stem wall, is wicking up wall a bit without enough or proper capillary break. Perhaps a few inch wide and couple inch deep gap around perimeter between gravel and concrete would provide enough capillary break? Or at least even raked next to perimeter to loosen up the gravel a bit I'm thinking?

      The stem walls are 2 ft high in a new build 40x60 slab on grade shop, poured over the summer and completely dry except for rain/snow moisture wicking up about 5" or so on the exterior (grade starts at bottom of slab and goes up about 5" also inside). We haven't seen any moisture inside yet and were going to epoxy slab and stem wall. We put down a real good commercial grade vapor barrier under slab with super low perm. Black stuff painted on exterior below grade. No insulation on 2 ft inner stem wall then rest of way up 14 ft framed wall will be dense packed blown in fiberglass...except a bathroom portion with a furred out wall that will also have closed cell spray foam on only that room's lower portion of the 2 ft stem wall.

      Please let me know if I'm still being confusing and clear anything up. I just really appreciate perspective and help :) Wish I could get you pictures!

  2. Deleted | | #2


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