Detached garage renovation into living space

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Michael Korbel

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Traverse City Michigan
Hello all. I came here to these forums to seek advice from good folks like yourself.

In 2014 I bought property which included a 30x40 building. It has a concrete floor with a perimeter of one layer concrete brick, and then 2x6 construction above. When I purchased the building, there were 2 rooms framed out, which I later expanded upon. The building was also insulated prior to purchase with pink insulation. I ran electricity to the building and wired it all up. I used Red Guard and coated the whole garage and then tiled directly over that.

Problem I'm having now is high humidity in the building. My humidity guage is reading 89% humidity for days on end. I saw some mold build up on the drywall which I cleaned with bleach and used Kilz2 paint to cover. I have since put in a 750cfm fan to help keep air moving but there is still high humidity and also looks like spots of water on the concrete/RedGuard where I haven't finished tiling.

The concrete is cold to the touch and the air yesterday was 81degreesF. Is this humidity caused from the cold floor meeting the warm air? How do I combat or solve this issue? Should I insulate the floor? Getting nervous because I don't want to ruin my investment on this building. Any thoughts help--Thanks in advance--Cheers.


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Retired Defense Industry Engineer xxx
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New England
It's prudent to insulate the ground and provide a moisture barrier prior to installing the concrete slab. If that wasn't done, there are two possibilities for the moisture:
- condensation. Note, the higher the air infiltration, the more there can be
- ground water.

One other thing to look at is the grading around the outside of the building and the use of gutters, and how they direct the water away from the building.

FWIW, Redgard won't work well as a moisture barrier if there's a high vapor pressure from below. It can work as a crack isolation layer. That may have not been the best choice, depending on the circumstances.

Do the walls have a vapor barrier on them? WHat about a house wrap on the outside?
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