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not-real-handy 08-22-2009 11:48 AM

Bathroom ceiling painting
 
There are black spots appearing above the shower in our bathroom. No doubt caused by moisture. We have an old house in VT. When I added insulation to the house years ago, I added some plastic dryer hose to the bathroom fan exhaust so the moisture would exit well above the insulation. I was then told by a guy at work that the moisture blowing through the dryer vent would condense in the colder months (lots of those in VT) and freeze up/ run back into the fan etc. So for a number of years, we haven't used the fans in the colder months. (Getting to the fans in the is a real bear) So now I have mildew on a rough ceiling surface...not sure if it's popcorn texture or whatever but it's not smooth.

I've read some posts here and realize I need to dry the bathroom out really well before priming w/ Zinnser Cover Stain Oil Primer. Then I need to let that dry really welld before painting over w/ a Sherwin Williams bathroom ceiling paint. Then I need to let that dry really well before using the shower. Got it.

I have three questions:

1) How do I prepare a rough ceiling surface for priming?

2) Is the dryer vent extension really a bad idea? I've taken it on faith that they guy at work knows what he's talking about and it sounds logical.

3) Have I missed anything?

Thanks!

ccarlisle 08-22-2009 12:01 PM

#2 - your friend is right. Bad idea in our climate just extending the vent to the attic and then not using it. Can't you access a fan through the roof?

not-real-handy 08-22-2009 12:07 PM

Our house has a slate roof and I'm not touching that for love or money.

Which do you think would be better:

Remove the extension and let the moisture vent into the attic (unheated and fairly drafty since it's a slate roof)

or

Use some sort of insulated extension?

Scuba_Dave 08-22-2009 12:11 PM

Yeah - you need to exhaust the moist air outside of the house
Otherwise the moisture will penetrate the insulation
You could rot out the roof decking by venting moist air into the attic
And mold will grow

Make sure the paint has mold/mildew preventer/additives

ccarlisle 08-23-2009 08:17 AM

Knowing you have a slate roof, I'd be extra careful about where I vented that fan because a roof tear-down of a slate roof isn't done with spare change. I'm not saying that the roof will fall in on you, but I personally feel that any roof is only as good as the structure and materials used underneath it, so creating a mould zone doesn't turn my crank. I am sure guys like Ed the Roofer on the Roofing forum could tell you more about that, but to me it's just not a good idea.

So if you still don't want to insert a vent in the slate, what about the soffits? Seems to me like doing something like that is actually killing two birds with one stone: humidity problem and extending the lifetime of your roof.

Look, at worst, the cost of installing a vent in the soffit might run you a half-day's pay for two guys...say $500. How would that compare to a roof job? I guess it depends on how long you want to stay in that house, but also consider the resale value of your house if you do nothing. :whistling2:

chrisn 08-23-2009 06:30 PM

Look, at worst, the cost of installing a vent in the soffit might run you a half-day's pay for two guys...say $500. How would that compare to a roof job?


Trust me on this, you do NOT want to go there,( new roof):no: especially if it is asbestos coated slate which is very common but not well known.


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