I live in Connecticut and have a bathroom vapor barrier dilemma.
I just started remodeling a small bathroom (4 ft x 4 ft) with a single tiled shower attached. Two of the bathroom walls are exterior walls. In the past these two walls have had water vapor problems – paint peeling from the exterior siding but no mold or rot inside. The bathroom does have a ventilation fan.
During the remodeling my building supply house suggested unfaced insulation with a plastic 6 mil vapor barrier on the walls instead of the standard kraft faced insulation. Sounded like a good idea. This weekend I insulated the bays, attached the plastic, and put up the sheetrock.
This solution came up yesterday in a discussion as a very bad technique since any water vapor that penetrates the sheetrock will condensate on the plastic and migrate down to the subflooring and eventually rot the floor area.
My dilemma, should I rip out the sheetrock and use kraft faced insulation or stick with the plastic? I have also considered priming the sheetrock with an oil base primer to create an interior type vapor barrier/retarder.
Your suggestions would be greatly appreciated.
Thanks.
Replies
Nothing wrong with what you're doing (required practice here, in fact) EXCEPT behind tile in a shower enclosure, where some ventillation (furring away from the VB, eg) may be desired.
Thanks DanH.The vapor barrier is not behind the shower stall - the bathroom walls are the exterior walls. Luckly the shower walls are on the interior of the house.Thanks for you time and advice.Daz867
why are you using sheetrock
.
Y not?
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The way you did it is right. any moisture the SR takes on will dry back to the room again - IF you let the room itself dry and vent
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Piffin,Thank you for your time and advice. I didnt want to tear out all my work.Daz867
>>This solution came up yesterday in a discussion as a very bad technique since any water vapor that penetrates the sheetrock will condensate on the plastic and migrate down to the subflooring and eventually rot the floor area.<<
The plastic vapor barrier, installed just prior to the sheetrock is correct. It prevents the moisture penetrating into the insulated stud cavity space etc. If trapped here you stand a very good chance of growing mushrooms within the wall cavity space.
Are the two outside walls you mention shower walls? If they are, you should not be using sheetrock. Instead you should use Durock or cement board and tile the shower walls. If the two outside walls you mention are not shower walls, you may be concerned that your exhaust fan may not exhaust out the moisture in the air after a shower. Either leave the fan on longer after you're done in the bathroom, or replace with a exhaust fan with more CFM exhaust power.
JoeArchitect,Thank you for your time and advice.The two exterior walls are the bathroom walls. Luckily the shower walls are on the interior. I appreciate your thoughts - I didnt want to tear out my work.Thanks. Daz867
Your plan is fine, assuming you have something more substantial behind the shower walls. You shouldn't have condensation on the room side of the poly sheeting if the insulation is done properly. In your case, the cold plane where moisture would condense is on the inside of the exterior sheathing. The poly is supposed to keep the vapor away from there. A leak in your exterior siding is another issue althogether. As far as drywall coatings go, a decent latex finish should be sufficient, oil is not necessary. In fact, oil based paints are becoming a thing of the past. Stricter air regulations for VOC have been put in place in a lot of states (NH's just went into effect on Jan 1, 07). Not sure about the other New England states but since NH is usually one of the last states to do anything like this, my guess is that there are already regs in place in most of New England already.
RedfordHenry,Thanks for your thoughts. The shower tile is on the interior walls and has been in for 40 yrs. Hopefully that will continue to hold. The exterior bathroom walls are the problem. From your inputs and others I am going to contuinue with the plastic.Thanks for your time and suggestions.Daz867