drywall - House Construction?

Question

At one time they use to make sheetrock with plastic sheeting on the back side for use as basement walls. It was supposed to block humidity. But is it recommended for ceilings?

I have ceiling sheetrock of that type in my house and mildew spots on the ceiling and walls that keep coming back. That part of the house is over a 2-car garage that is indeed damp. Could that vapor barrier be trapping humidity?

Any advice would be appreciated.

regards,
andrew

Answer 1

Unfortunately you will have to remove your drywall and find out what is happening. There is a possibility water is finding it's way in. It could be coming from your roof which may not have a roofing felt (black tar) paper layed down or even flashing before your shingles were installed or even badly installed gutters may be the problem. Do you have insulation with a plastic vapour barrier this should protect against moisture. This problem is easy to resolve but you need to tear out your walls first to determine the cause. I have a bedroom above my garage and never had any problems.

http://oikos.com/esb/30/atticvent.html

http://www.hometips.com/content/flashing_intro.html

Answer 2

Typically you would use plastic definitely as a vapor barrier covering insulation then the drywall would be attached to the studs. It sounds like you have other issues other than the dampness of the garage. You could try adding some sort of exhaust system for the attic space above the room that would let the moisture escape by evaporating. I would use the plastic as the vapor barrier for the ceiling and the walls, but I would also replace the insulation that way you are starting from scratch.

Answer 3

When they normally build houses, they put up insulation and then poly over the insulation and then the sheet rock.
In otherwords no different than what you are doing.
Your problem has more to do with ventilation in that room--you don't have any air moving around.
If anything,the ceiling below in the garage probably does not have poly or plastic on it so the moisture is migrating upstairs. You got one big steam room. Either have you windows open just a crack all the time so that fresh air comes in, and/or have a fan blowing in the room 24/7 or maybe a ceiling fan running constantly.
As for the mildew, it is something you just can't put latex over and hide it. It will burn thru the new coat of paint.
Use a stainblocker called KILZ, General Paint should have it. Use a spray can and spray it on the stain first....you are basically giving it a coat of glass first. And nothing can get thru glass. Then when you paint you are painting ontop of the "glass". Your coat of paint will not suffer from mold bleed thru.

Answer 4

sounds like either moisture is rising up from the garage and getting trapped in the warm air of your room, or too much insulation and too little ventilation in the attic above the room. does the room face south or southwest? sunlight could be adding to the problem by heating up the room if the room has a lot of windows. all of this is assuming that the roof is in good shape, the gutters are clean, and you have no ice dams if you live in a cold climate. as far as the vapor barrier behind the sheet rock goes, whether it be plastic or kraft paper, most all new construction seals a room so that moisture from inside does not condense in the cold outside of the room behind the walls or above the ceiling. so, if the roof and all are fine, and you think the attic is ventilated well, i would make sure that you have a vapor barrier between the garage and the living space first. good luck, hope this helps.

Answer 5

I think the most important thing that you should do is to find out where your moisture problem is coming from and fix it. Usually a vapor barrier is a good thing, that it allows a bit of air to circulate and dry up any dampness.
Good Luck!!
I've never seen the sheetrock you are referring to with the plastic backing~

Answer 6

Although I've never heard of the drywall you are referring too, I do know they make the green-board moisture resistant drywall and now they also make a drywall that has no paper facing at all that is mildew proof. Lowes was advertising it just last week in their circular. But to reinforce what was said earlier, you're treating the symptom and not the source of the moisture/mildew problem.