Condensation on Garage Ceiling

Old 03-11-08, 08:53 AM
Thread Starter
Join Date: Mar 2008
Posts: 1
Received 0 Votes on 0 Posts
Condensation on Garage Ceiling

We had our home re-roofed in Sept (hail damage) and the roofer added a ridge vent over our attached garage. With wintertime now hear, we're seeing moisture stains on the interior of our sheetrocked garage ceiling.

What I think is happening is that the attic - with the new ridge vents - is more like the outside temperature. When the warm cars pull in, the hot air rises and the moisture it contains then condenses along the seams of the sheetrock. The order and placement of the water stains (along with the weather conditions) appears to bear this out. The problem only appears when we have very specific weather conditions where it's cold in the attic and warmer in the garage. It gets worse the colder it gets. [One way we've tried to mitigate the problem is leaving the garage door open until the cars cool.]

The garage has ceiling 2x10 ceiling joists, 16" OC and no vapor barrier or insulation. There's not much space in the garage attic to move around in, so I'd prefer to work from the garage interior to solve the problem if at all possible.

One idea I've had is to use a vapor barrier paint on the ceiling and, say, the first foot or two down from there. This at least would keep the condensation away from the ceiling's sheetrock, but I'm concerned that the moisture would just form and roll down the wall, moving the problem rather than solving it.

Another idea I've had is venting the garage space, but here the problem would be getting into masonry work (brick home), cutting a hole in the roof (undesirable choice), or maybe having the garage vented into the stack for the water heater (in our part of TX, water heaters are typically in the garage attic). I thought the use of the water heater stack might be a code violation so I sent a note asking, but haven't heard back.

Ideas on how to proceed would be much appreciated.

Old 03-11-08, 03:28 PM
Join Date: Oct 2006
Location: Wilmington
Posts: 4,214
Received 0 Votes on 0 Posts
Are you sure the stains are not coming from above, as in a leak in the new roof or the ridge vent??? If nothing else has changed other than the roof/vent, I don't see your problem as being related to the roof. Do not vent into another appliance vent, not allowed under most codes.
Old 03-11-08, 03:53 PM
Join Date: Mar 2005
Location: USA
Posts: 6,130
Received 0 Votes on 0 Posts
Condensation on Garage Ceiling

Your roof vents are working exactly the way they were intended to. They are keeping the space above the ceiling at about the same temperature as the exterior.

You need a vapor barrier and insulation above the ceiling to give you a comfortable garage summer and winter.

Thread Tools
Search this Thread
Ask a Question
Question Title: