Damp garage floor 2 years after construction

flatheadOctober 5, 2005

I'm looking for information on how to address damp spots on my garage floor that don't appear to be condensation - could it be moisture from ground below? 3 yrs. ago I hired a garage contractor who talked me into using a concrete additive that he claimed would waterproof the concrete - he refused to put in a plastic moisture barrier, for some reason. And this guy was recommended to me by a friend... who also didn't get a moisture barrier. One year ago, beginning in the winter (wet season in Seattle) I began seeing dark, damp streaks and blotches appearing somewhat randomly on the floor. The spots are still there after a dry spring and summer. Where the concrete is not darkened, it appears to be quite dry (majority of the floor area). The garage is closed up almost all the time and is pretty tight. A thermo/hygrometer shows that it's usually 60-64 and high humidity (60+ %) in there. Aggravating factor: 20-ft. concrete driveway slopes downhill from alley to garage, dropping 3 ft., drains into a french drain that empties into a dry well beside the garage. I don't get rain water under the garage door, ever, but with the ground surface's steep grade above and next to the slab, could there be ground water moving under the driveway and then under the slab? Funny thing about the spots is - though they seemed random at first, I noticed they seem to coincide with the marks left behind by the plastic sheeting that the concrete guy put *over* the freshly poured slab to help slow down the drying. What could be the connection? Could the moisture be coming from above (from constant high relative humidity in garage) and the spots coinciding with where the surface texture of the floor is different due to contact with a plastic sheet? That would seem highly unlikely to me, but...

Thanks in advance

Thank you for reporting this comment. Undo
manhattan42

If the garage is detached or attached, there is no requirement to have a vapor retarder under the slab.

The exception is if the garage is located under habitable space above, the garage floor needs to be treated like a basement floor and a vapor retarder would be required under the concrete.

At any rate, it does sound as if water is wicking up through the concrete slab. Concrete is porous and is permeable to water and ground water vapor.

Sure sounds like you are developing wet spots because of either water table rises, wicking water, runoff or condensation of vapor within the slab.

    Bookmark   October 6, 2005 at 9:09PM
Thank you for reporting this comment. Undo
flathead

Thank you for the reply, manhattan42. Garage is attached, has living space above and interior stairs. The contractor never cited building code, just said the plastic barrier was not needed and his policy was to not use them in order to minimize wait time for the concrete to dry. I don't know what UBC says (this county goes by it pretty much, I now know) but if it says you must have vapor barrier below living space then this work shouldn't have even passed my city's inspection. And as far as the waterproofing "additive" goes I guess that was a total fraud.

So what are my options for eliminating the wicking water?

    Bookmark   October 7, 2005 at 5:06PM
Thank you for reporting this comment. Undo
bus_driver

In my attached garage, floor above grade, my humidity meter in the Summer usually reads 70 to 85%. We keep the doors closed most of the time for security reasons. I used 4 layers of 7.5 mil poly under the concrete, so it really has a barrier. A dehumidifier would be the only answer for my situation and probably for yours.

    Bookmark   October 8, 2005 at 7:52AM
Thank you for reporting this comment. Undo
manhattan42

A minimum of a 6 mil vapor barrier would have been required under this concrete slab and it appears that this code violation slipped past the inspectors.

It is also nonsense that keeping the vapor barrier under the concrete will increase curing times. Concrete cures by chemical reaction, not by evaporation.

Be that as it may, you could use an epoxy based water and vapor proofing coating for your garage floor.

It won't stop water getting into your slab, but it will prevent liquid water and ground water vapor from penetrating up through the slab.

    Bookmark   October 8, 2005 at 11:13AM
Thank you for reporting this comment. Undo
GDS_

I eliminated my moist garage by instlling a cheap bedroom type ceiling fan on the ceiling of the garage. I turn it on high, and leave it on all spring, summer and fall, and I have no moisture at all.
It won't solve your problem, but it might help aleviate it.

    Bookmark   October 9, 2005 at 9:51PM
Thank you for reporting this comment. Undo
flathead

Great responses, thanks to you all! I'll do some looking into the code issue, can't understand why this supposedly reputable contractor would have poured a slab without a vapor barrier. The epoxy coating may be the solution.

    Bookmark   October 13, 2005 at 2:58PM
Thank you for reporting this comment. Undo
galotoczky_wowway_com

Would installing a ventilation fan into the roof of the garage help the problem? I was thinking about one of those solar powered units. any thoughts?

    Bookmark   October 14, 2005 at 9:34AM
Thank you for reporting this comment. Undo
sdello

"Be that as it may, you could use an epoxy based water and vapor proofing coating for your garage floor.

It won't stop water getting into your slab, but it will prevent liquid water and ground water vapor from penetrating up through the slab"

Depending on the vapor drive through the slab you may end up with blisters under the coating as the moisture reaches the top of the slab and debonds the coating locally at first and then growing laterally.

If the moisture is really troublesome then I would suggest the dehumidifier.

    Bookmark   October 14, 2005 at 10:27AM
Thank you for reporting this comment. Undo
bus_driver

I forgot to mention that the walls and ceiling of my garage are finished with drywall, just like the interior of our living space. The garage is fully insulated, including the doors. The drywall finisher I hired for the garage actually did better work than the one who did the house.

    Bookmark   October 15, 2005 at 1:54PM
Thank you for reporting this comment. Undo
tcgoff_hotmail_com

Did you ever get your damp garage floor fixed?

    Bookmark   October 5, 2008 at 4:24PM
Thank you for reporting this comment. Undo
SeattleSurfaces

There are many products available that would help with your problem. You can get moisture barriers that will withstand 20# of water pressure per sq. ft. per 24 hour period. You can then coat the surface with an epoxy, an overlay, or whatever to get to your desired finish floor.

To simply say an epoxy will fail because of moisture is wrong. An improperly installed epoxy will fail, as will almost any other type of floor covering. If done correctly, you can have a beautiful floor that will remain dry and last indefinitely.

A de-humidifier will only make a moisture problem less visible. It will do very little to fix it.

    Bookmark   October 21, 2011 at 6:30PM
Sign Up to comment
More Discussions
Gable Vent Color Suggestions- Insight please
Hopefully someone can give me insight! We recently...
storyta
Moss removal help!
Can anyone tell me how to effectively remove what looks...
nycbride07
How to fix 1" gaps in drywall seams?
We recently bought our home (build in 1938). One of...
Bongo
T1-11 siding: Replacing rusted z-flashing?
I have several questions about z-flashing for T1-11...
rogerv_gw
adjusting stop on lazy susan
Hi all, I have recently moved into an older home with...
blakekr
Sponsored Products
Align 4 Piece Leather Sectional Sofa in White
$1,299.00 | LexMod
Designer Eco-friendly Pet Door Mat
Grandin Road
Mont Blanc Satin Nickel Three-Light Vanity
$123.00 | Bellacor
GE Under Cabinet Lighting 13 in. Fluorescent Light Fixture White 16029
$23.97 | Home Depot
Exos Delta Adjustable Pendant by Hubbardton Forge
$452.00 | Lumens
Magic Garden Step Stool
Classic Hostess
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™