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Hi folks, I need some advice on how to fix my humidity problem. My free-standing shop has a slab floor, with no poly under it, basically because the concrete guy told me it wasn't necessary when I built it 3 years ago. Live and learn I guess. I am having a hard time keeping the RH below 60%, with a large dehumidifier running constantly. I assume the moisture is coming through the slab, as the walls and ceiling are well insulated and have a poly vapor barrier taped at the seams. Also, when the slab was new I applied some sort of sealer to it; I think it worked as water beaded up on it for a while.

Would painting the floor, or epoxy coating it work to reduce the transfer of vapor up through the slab, and what's the likelihood that that action will cause the coating to lift and peel over time? Anything else to try?

Thanks!

Most of the painted concrete I have seen peels off after a few years, so maybe one of those epoxy coatings. What about putting a wood floor down with vapor barrier underneath? Costs... but might be worth it in the long run.

I have an endless pool swimming pool in my sunroom with a dehumidifier and it never gets above 50%. I think you may need a better dehumidifier. I got a #1DGX5 Dayton dehumidifier thru Grainger. You set the Humidity at where you want it at the upper limit and it keeps it there. I may need to dump it every 2-3 days day...or once a week depending on the usage of the pool. I just can't image a garage would absorb more moisture than a swimming pool.

How often do you need to dump the water...or does it have a drain?

Have you discussed (with the wife) the option of a shop in the bedroom?
Kent

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Wood Creations by Kent A. Bailey
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Epoxy floor paint is the ticket. As previously stated prep is key. You must get every bit of grease and oil off. Check with the paint maker. You want the two part epoxy paint not the stuff that says it has epoxy in it. You need to use the correct chemical filter or it will blow you out of the building and you won't have enough brain cells left to build a decent guitar. Here are a couple of sources. It goes on good with a paint roller with a 6' stick screwed into it. As horrible as it stinks when applying it is almost totally inert in a few days. Even if there were plastic under your slab they tend to get holes punched in them by rebar, being trampled during the pour etc. I can assure you you are getting moisture coming up from the earth.


http://floorepoxy.com/cgi-bin/shop/cart.cgi
http://www.epoxy-coat.com/?src=google&k ... iAodY32-_g

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You can tape a small square of plastic sheeting down to the floor with a moisture proof tape for a few days. If moisture is coming up through the slab, it will show up as condensation under the plastic.

I used an acid wash on the garage floor before using epoxy paint. The muriatic acid is pretty nasty stuff so take all suggested precautions with it. The epoxy paint has held up well for 15 years so far.