Just looked at a large bathroom where the folks want a bath fan added. The walls and ceiling are plaster over blueboard. The paint on the lid is peeling somewhat over the shower (at one end of the room) and to a lesser degree over the tub (at the other end). In both cases there are recessed lights and the peeling is occurring around those lights. I’ve gotta think there’s a relationship here between the lights and the peeling, maybe that the heating of the ceiling when the lights are on is somehow involved, or the penetrations in the lid are allowing moisture in. Just a vague hunch… anyone with some real knowledge?
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My guess is moist air leaking through the penetration and condensing around the fixtures in the attic creating a moisture problem behind the paint.
-a paint unfriendly situation. You might consider cement board and ceramic tile at shower area ceiling. I don't think the vent fan is ticket out of this - help, yes. Depending on family size, shower habits, etc, and other factors paint probably won't cut it this location (my opinion).
Probably moist air leaking up there as was said. If the plaster is sound and you can get good adhesion the fan will probably take care of most of the problem (if they use it). Will help if the fan has a humidistat switch or at least a timer switch.
In this situation, if there previously was no fan then it's amazing the paint would stay up at all.
Any new paint that's applied should be mold-resistant or have a fungicide mixed in it before application.
Sounds like we have some consensus on the air/moisture leakage issue. More details: There is accessible attic space above this bathroom and the can lights are all visible up there. There is a layer of poly between the ceiling blueboard and the joists. There is a layer of R-19 FG with the kraft side down, between the joists. The attic space is not vented and is not heated. Access is from conditioned space.
So... the attic space is cold and damp much of the year (this is coastal WA, right on the water). The bathroom is warm and damp. The can lights are hot and heat the lid around them. Is there a condensation problem? Seems like moisture would condense inside the can, if it's moisture from the warm area seeking a cold surface for a dew point. I can easily see how moisture condensing on the outside of the can would find its way into the core of the blueboard and peel the paint, especially with that poly there.
Someone with some building science know-how... hit me.
not science, just a thought - how hot are those lights? The combination of moisture and heat might be "cooking" the paint. Either way, the fan install is going to make things better. Maybe lower wattge lighting could help with temp differential too.
All ideas are good............also consider that plaster has a cure before painting wait..........I believe.
Mike Smith would know this. If the paint was applied to soon, it ain't gonna help matters.
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
The house is 20 years old. The plaster should definitely be cured by now, but I'm concerned that they used a less-than-ideal primer for plaster. I've had some problems with primers sticking to USG Diamond Finish, and next time I do it I'm going with USG's own primer for their plaster.
Moisture condenses inside the can, but as soon as you turn the light on the heat drives the moisture out and into the surrounding area. Probably a lot gets caught under the plastic (are the cans covered by plastic?) and soaks back into the blueboard.Simply removing the plastic within a food or so of the cans would probably help quite a bit. Also, it would be a good idea to box in the cans with drywall, sealing them tightly. As it is they're a major air leak into the attic.
I think DanH is on target.Alternatively....you do not describe how close the insulation is installed to the lights. If the insulation is kept back aways from the light (it usually is since the light has to be IC rated to be in contact witht he insulation) then there is a cool spot on the ceiling for condensation.Rich BeckmanAnother day, another tool.
I suggested the shower trim to them, and explained the condensation thing. It was also suggested to build baffle boxes over the lights, in the attic, which makes a helluva lotta sense. I framed in the fan for them this morning, so my part is done.
Sealed can trims for bathrooms are available, they have a frosted glass lens and gasket to the ceiling to stop air and moisture escaping upward. I like wiring the fan to go on with the lights ensures it's use.