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I have a very small shop area where I keep my wood & parts and do any assembly. For the first time I am having trouble controlling the humidity. The room is only 8X10 and well insulated, but with 3 exterior walls. I did the insulation and sheetrocking myself and didn't know I was going to be building guitars back then, or I would have done some kind of moisture barrier. The floor is a concrete slab. Here in AZ I've never had a problem before, but we've been having an unusual amount of rain this winter, and even though I have had a dehumidifier running 24 hrs a day, I can't get it down below 50-55%. I usually like to build at 40-45%. I'm thinking about sealing the floor so my questions are: What is the best product to seal it with? Is it going to make a significant enough difference to be worth the trouble? How long will it take for the fumes to clear out if I allow a lot of air circulation? I'm not looking forward to long term fumes since I seem to be developing some chemical sensitivities. Anybody have any experience with concrete floors in their shops? Any advice is appreciated, Wendy

I was on a concrete slab built in the 40's or so, and near the SF Bay where the water table is near the surface. I ran multiple dehumidifiers around the clock.

Probably an epoxy sealer will give you the best barrier, although they are harder to apply than some others. Ask a contractor.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

My shop is all concrete floors. The large portion is heated in the winter and dehumidified in the summer so this staves off any moisture issues leaching up through the concrete.

I put in a false raised floor in my climate controlled wood room and that stopped the moisture problems for me. This is what I did: Lay down a single sheet of heavy visqueen plastic directly on the concrete (no sealing is necessary), lay it wall to wall and up the walls 18". Do this twice. Now lay down 2" x 4" joists, insulate between them and add two more layers of visqueen on top of the joists, add 3/4" sub floor, one more layer of visqueen and final flooring. It may sound like overkill but the room is air tight to the max. I should add that the walls and ceiling were stripped, insulated, two layers of visqueen then 1/2" sheet rock over the top. I could probably pull a pretty decent vacuum in there too

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tim...
http://www.mcknightguitars.com

Here is another alternative…
I finished my basement floors by laying down pressure treated 1” X 1 ½ “ sleepers 16” O.C. Then I used a thick poly sheet pulled taught followed by plywood. The poly sheet keeps the moister at bay while the sleepers provide an air space under the poly. It works like a charm at keeping my basement dry plus it gets me off the concrete floor and it is also relatively inexpensive to do.

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Rich S

"The inconvenience of poor quality will linger long after the thrill of a bargain has been forgotten"

Trouble dehumidifying in AZ? Who'd a thought?

I painted the floor of my basement shop, where either the humidifier or dehumidifier is running for about 300 days/year. I do believe it cut down on the moisture swings a bit. In the end, I think it is an easier floor to clean, too, which is helpful, plus it brightens the room if you use a light color.

Jim

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Jim Kirby
kirby@udel.edu

Wow, Tim and Rich, those are 2 really good solutions that I might consider in the future when I have more time. I was kind of looking for a quick fix for now to get me through the work that is in progress, before I have to move everything out of there to do a major upgrade. I thought if I were to paint the floor with some kind of epoxy enamel I would only have to move everything to one side, seal and let dry, and then move everything to the other side to do the other 1/2. And by the way Jim, the climate here in the desert has changed as much as everywhere else. I was hiking last weekend in the now GREEN desert, and there were rushing streams everywhere. Usually I only have to worry about humidity during the summer monsoon season, and then the AC takes care of it. Thanks everyone.

I sealed my concrete shop floor with epoxy paint and it really helped to control the excess humidity infiltration. Most epoxy paints require that the floor be acid cleaned first. You should probably empty your shop before you do the acid wash and painting.