humidity in detached garage

Hi all,
I have a detached garage which is actually two stories. It's very well insulated (better than the house) and the garage bay stays very cool even in the summer. Probably because I have tons of trees and there's only one window into the lower level. I was just in there the other day and found it to be very damp. I'm assuming that this is just naturally what happens when it's 90+ outside and you have a space that is maybe 65-70 degrees. Would you concur, or do you think that this will go away now that I've almost completed properly grading the land around it? (previously it was bad, dirt piled up well over slab level against the walls and sloping in. I've removed a LOT of dirt.)
I'm thinking that even with the grading, it'll require a dehumidifier to be properly conditioned for storage of a nice car. I'm also assuming I should buy a "low temp" model in case I feel the need to run it in the winter (no heat) suggestions on model? Was thinking of something like this:
http://www.ajmadison.com/cgi-bin/ajmadison/AD35USS.html
thanks
nate
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It will work but moisture comes up through concrete consider painting it with epoxy
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"ransley" wrote

Can you recommend a brand for use inside? I'm about to go to the local HW store. My sunroom addition floor has mild cracks (always has, long ago settling) and in a few spots we get seepage.
The cement slab is not super smooth. The cracks are at most 1/32nd inch and have been stable since I got the house in 1995.
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cshenk wrote:

If you've got active seepage, I wouldn't put down *any* kind of floor covering. A film covering, like paint, will just get water blisters underneath, even with an epoxy paint. Carpet, vinyl, or wood will hold the moisture and promote mildew.
See if you can correct the problem that's letting the water in. Maybe you just need to change the slope of your yard a little so water flows away from the foundation.
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"SteveB" wrote

Actually, we just got a good sealant just for this. Turns out there was little difference in inside types and exterior types.
The 'seepage' is very minimal. More of a darkening along that area in truely soaking long rains. Only a few spots and not directly at the wall portions. This is apparenly a fairly common issue in my area with the slab construction and porch extensions added 20 years ago like mine. House is fine BTW, just the extension has this. It was poured 'thinner' than a full house slab so the porch is about 1.5 inches lower than the house and about 1.5 above the ground outside it. Not sure how deep it is, but the cracking is very minimal and has not changed in the past 13 years nor has the nominal seepage from ground water in heavy rain. We just never bothered to try a sealer before. The sunroom was poured to be about 3/4 inch above the porch, and 3/4 below the house but was done with an added layer. Initially, it was also screened porch then later raised and enclosed.

Short of a major rip out and repour of the extension, there is little to be done in that vein. This is a high water table area. Think something like New Orleans and you'll have it close? It's recovered swamp land. I did however check on this some years back (1998?)and you'd be dead on correct in most cases. No way you could have known my water table is this high and that my friend, is the issue this time.
All gutters already set to direct away from the house. Yard is mostly flat with a slight sloping rising around the house as a water barrier. Drains along the side and to the front yard then down the street gutters. The only 'low spot' that can be a problem is the opposite side from the sunroom where the screened porch door leads to outside. In hurricanes, the water there rises a bit and can lap over into the screened porch. Placing a level along this added porch slab, shows a very fine grade to make that the low spot where the rain drains out. The addition of a brick walkway later made a barrier so that water will collect on that side just enough to come into the porch but it takes a hurricane level of rain to happen. (We are considering removing that brickwork and using paving stones instead with 1 inch gaps between them and a runnel to that side of the house so it flows away better).
What is not good here, would be a carpet underlayment. That might mold I think. We know it did in the past as we had that taken out when we got back from overseas and the room was mold damaged. Renters put in an indoor carpet with underlayment in the sunroom. Bad juju there. The main damage though was because they failed to caulk the exterior of the old 'sunroom' and it was improperly built so the walls rotted out. New walls are now in place and all is well.
What works for the porch and the sunroom, is carpet meant for outdoor use (such as you might put around an outdoor pool). For the screened porch, we have a 'green grass' sort of carpet arriving, and for the sunroom, one that looks a bit like brownish berber but made for *outdoor* use. Looks like inside carpet pretty much but made to withstand getting wet all the time.
We had a green 'grass' carpet in both rooms when we left and it was never a problem.
(They apparently put out cigarettes in the porch carpet for years so it was removed by the rental agent before we got back but he said it was not a mold issue, more just careless burns all over it).
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OK all, point taken about the epoxy floor coating and that is something that I want to do anyway, but not right now (there's a disassembled Corrado in the garage at the moment, among other things.) So today I stopped at Lowe's and picked up a Frigidaire brand dehumidifier, I think it is this one:
http://www.ajmadison.com/cgi-bin/ajmadison/FDF50S1.html
My thought was that during the summer I would leave it in the basement of the house, then either buy another new one in the winter or if I'm feeling frugal, swap them so the low-temp rated one is in the garage - reason for doing this is I currently have a really old thing that's loud and makes it hard to watch TV when it runs (heh, it just kicked on as I'm typing this.) It doesn't run that often, but it is necessary - it gets noticeably damp if I shut it off for a week or so. I've wanted to replace it for a while now because of the noise, I just didn't have an excuse to buy a new one until I noticed that the garage was a little damp as well.
Anyway, I'm taking the Frigidaire back, because the "bucket full" switch doesn't work - a little thing, I know, but I'm not real diligent about checking it, because, as I said, it doesn't run that often. Something that it does I don't like though - it seems that the fan runs continuously as well, whether or not the compressor is engaged. Does this sound right to you guys? I'm not sure if I should exchange it for another one or get my money back. If it *is* supposed to run the fan all the time, are there any models that don't do that? I'd prefer to have one that only runs when it has to, because I like a quiet house, and don't like unnecessarily wasting energy (I leave the furnace fan on to keep the air circulating, so having a fan in the dehumidifier running 24/7 is redundant.)
In the Frigidaire's defense, it is fairly quiet when it is running, although the fan is somewhat loud. That's less offensive to my ears than a rattly compressor at least.
thanks
nate
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Any input? Sent an inquiry through Frigidaire's web site last night, no response yet. Can't figure out how to speak with a human through the phone no. on Frigidaire's web site.
nate
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Any input? Still no reply from Frigidaire/Electrolux. It's packed up and in my car, to be returned after work today, but would like to know whether I should exchange it or just get my money back. It'll be the latter unless someone can confirm that this unit is actually intended to work the way I expect it to you (e.g. completely shuts off unless excess humidity is detected.)
Can anyone recommend a good, quiet dehumidifier that's reasonably efficient and rated for low-temp operation?
nate
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"Nate Nagel" wrote

I think in winter you may not need a dehumidifier. Depends on how far north you are?
I also think Ransley nailed it with the dampness being up through the base as likely.
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