Vapor Barrier Compromised, need waterproofing advice

[beginner54]

Greetings. First post after lurking for a couple of years...

1. Building a 26x46 garage here in Seattle, WA area. Slab was poured one week ago and framing has begun:

2. Prior to pour my builder informed me the excavator I'd hired myself improperly backfilled the hole, using poorly compacted soil containing root and grass clumps mixed with gravel:

3. Rather than have excavator dig out entire cavity (which in retrospect I probably should have done), my builder designed a fix that involved digging a series of 6" round holes 30" deep and adding tons of rebar for reinforcement, essentially creating a series of piers or legs upon which the slab rests:

4. Structurally I'm confident the slab is stable, but I'm concerned about the 27 holes in vapor barrier created by piers. I know moisture can wick up through these spots, in fact several wet spots are still visible a week out:

These wet spots are gradually drying up and disappearing but I'm concerned about future water intrusion into building due to hydrostatic pressure and/or moisture in wet soil below vapor barrier (it rained a ton the week before pour.)

5. Knowing I'd be applying some kind of sealant my contractor had concrete guys rough trowel the slab, that is, not finished to super-smooth sheen.

6. My question is what you'd recommend for waterproofing the floor (with an eye on possibly doing some additional coating/finishing later.) I've started researching options and have had several recommendations: concrete supplier suggests a crystalline waterproofer called Xypex that sounds great but goes on ugly; a local flooring specialist recommends a silicate called Aquron CPT2000; another "authoritative" website recommends Lithi-Tek LS 9500... and the list goes on.

7. To complicate matters, I've had past serious health problems relating to mold exposure and other environmental agents so am extremely cautious about exposing myself to chemicals both during application process and afterwards. So something low in VOCs would be great. (I'd prefer to hire job out if affordable and if I'm confident in product and waterproofing specialist.)

8. Building is multi-use: light carpentry, parking, storage, tinkering space, office space... no lifts, oily work or welding planned.

Thanks for any advice your collective wisdom can offer... the options are mind-boggling and I want to avoid another bad decision leading to more headaches!

 

[LegacyIndustrial]

Those wet spots might represent the thickness of the slab on those areas. Not necessarily a problem at this point.

Options:
*Do nothing
*Apply a densifier (no waterproofing agents, will repel future coatings)
*Apply a breathable sealer (good ones are high VOC)
*Apply a true Moisture Vapor Barrier with an epoxy system over-top (low or no VOC if omit urethane/polyapartic topocoats)



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[Hilltopmasonry]

I agree that the wet spot is due to the fact that there is alot more concrete in that area and it takes alot longer for it to dry out. When i fill cmu walls with grout you can see the wet lines in the walls for a while exactly where the grout is filled




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[Radix2]

Vapor barrier effectiveness is based on total vs open areas.

In your case, with let's say 27- 7inch diameter holes - that is a total opening of 7.2 sq ft.

Your total area is 26x46 - 1196 sq feet.

The openings represent 7.2/1196. - .006

So your vapor barrier is 99.4% intact.

So stop worrying about it. .6% of the floor being permeable to the ground is not going to have a big effect on the inside environment imo.

 

[beginner54]

Thanks for your feedback and reassurances! I think I'll just wait a month and do a moisture test as described elsewhere in Forum and go from there.

LegacyIndustrial--you mentioned a "true Moisture Vapor Barrier" -- is this an undercoating or an actual paper membrane like you'd put under hardwood? Any links to specific product?

Thanks again!