Garage cantilever condensation source?

wwsteel

Hi,

So the garage is a two-part ceiling.

One part is the lower part near the big garage door, about 9 feet high, and the other part is the cantilever under under the bedroom and bathroom upstairs, about 12 feet high.

There is currently a lot of water damage due to the 6 mil poly being not installed properly in the 12' high cantilevered part. The poly is currently installed under the duct pipe, but I know it should be installed above the heat duct, so the hot air flows above the poly, not below.

My question is: Is it possible for several gallons of water to accumulate above within a short period of time (2 months in mid-winter) and eventually seap down to the drywall, and ruin it?

thanks for any input.

concretemasonry

Since you did not supply any information on the profile or elsewhere, where are you hiding (climate-wise)? and what is the cantilever built from. That will help to narrow the problem down with information.

A clearer description of the situation (photo, sketch, etc.) would put everyone closer to your situation.

Dick

wwsteel

Located in Edmonton Alberta, the climate this year has been more snowfall than usual, and very cold. Beyond -15c regularly.

The floor of the bedroom/bathroom is of wooden I-joists, 16" deep on 19" centers, and a 2x8" drop-ceiling on 24" centers.

The poly was installed underneath the heat ducts rather than on top of the heat ducts, which I have been told will cause condensation.

But, gallons of condensation?? Within 2 months?

Is it possible that moisture/precipitation got in through the roof via improperly installed vents, and caused major drywall damage?

Ron6519

It sounds like you have some large vapor barrier leaks and/or missing insulation.
Where do these heating ducts run?
In a cold zone?
Aren't they insulated?
Post some pictures.
Ron

jklingel

your condensation is more likely from poor air sealing than anything to do w/ the poly's position. poly is not likely necessary in alberta, though if installed in an airtight fashion it probably won't hurt. poly will not let vapor that sneaks into a space get back out so that the space can dry somewhat to the inside. check with local building officials to see if it is required. if not, consider taking it out and using a vapor permeable, airtight system instead. google "airtight drywall approach". there are others, too.