Why won't my paint stay attached to the wall?
September 10, 2011 12:03 PM   Subscribe

I need to repaint a section of damaged-and-repaired sheetrock above my shower, but I can't seem to get the primer (Killz, anti-fungal and water-based) to stick. It goes on okay, but peels away at a touch.

About a year ago, a hook (like a coathook) anchored in the sheetrock above my shower (it has tile going up to about a foot below the ceiling - Why they didn't do tile all the way up, you've got me) pulled loose, leaving a 2x3" crater. I patched it with joint compound, sanded the entire general section of wall (1x4ft), and repainted it.

About a month ago, I noticed some serious mildew growing on/in the area of the original damage, and realized I had just used plain ol' interior paint (the house came with a few cans in the basement, conveniently the right color) rather than one of those anti-fungal paints. So last week I sanded it down to the sheetrock again, bleached the hell out of it to kill any mold that had ideas of living in my wall, let it dry completely (then thoroughly wiped down the surface and let it dry completely again), and put on a nice thick coat of Killz. I also put a dehumidifier (set to 50%) in the bathroom, since it normally stays damp in there for a few hours after showering in the morning.

Except... I can't get the primer to stick! Twice now, when I go to sand it a bit to put on a second coat, it just peels away in big chunks. A few patchy spots (with nothing different about them I can see) will stay attached, but the vast majority of it just rolls and peels away.

Help! What can I do to get this stupid primer to stick?

As another bit of data for anyone who might have an idea, it seems stupid to me to use a water-based paint in the bathroom, but my SO would complain about the smell for months if I used something oil or solvent based. And the Killz label claims it works just fine in damp environments (really the whole reason anyone would use it, as far as I can tell).

Thanks, AskMe!
posted by pla to Home & Garden (8 answers total) 4 users marked this as a favorite
Best answer: Sounds like the joint compound is still a little damp. You probably need to stop showering in there for a few days to let it get bone dry before you put primer on. Generally, you want waterproof drywall above the shower. A big joint compound patch is not very waterproof, so you may want to consider cutting out a square section, replacing with waterproof drywall and starting again, especially if the area stays damp after showering for a while.
posted by ssg at 12:26 PM on September 10, 2011 [1 favorite]

If you end up using oil-based Kilz, you can significantly cut the odor by mixing a few drops of pure vanilla extract (as opposed to imitation vanilla) into the can first. (This trick also works for latex paint, by the way.)
posted by DrGail at 12:33 PM on September 10, 2011 [8 favorites]

Best answer: It's likely there's some soap or other residue left on the surface. I'd get some trisodium phosphate (TSP), sand off the primer that's been applied (as it will likely peel off at some point as well), and thoroughly clean the whole area with the TSP (directions on box). Allow it to completely dry (as in, don't take a shower in there for a day or two) and reapply the primer.

I had the peeling problem before a painter pointed out that the spray off of you in the shower isn't just water, it's carrying some of the soap that you are using, and that coats the walls and ceiling. Once I cleaned with the TSP, no problems.
posted by kjs3 at 12:39 PM on September 10, 2011 [2 favorites]

Response by poster: Thanks, all!

I did make sure to dry the spot, but not for a few days simply do to only having one shower. The SO plans to go away next week; I'll get some TSP, thoroughly wash the area down, crank the dehumidifier, and then see if I can stand washing up with the garden hose two mornings instead of the shower. :)

I agree that I may need to replace that section of drywall... I had hoped to get away with just a patch and sealing it with a good primer, but if nothing else, I suppose that would guarantee me a dry painting surface. If plan #1 fails, I'll keep that as a backup.

And if anyone else has any ideas, I'll leave the question open for now.
posted by pla at 4:26 PM on September 10, 2011

BIN primer has an alcohol-based version that will cover just about anything, so long as the surface of what you're painting is dry. That's what I would use. (A long, long time ago I worked as a professional house painter.) It smells horrible until it dries but thankfully it dries fast (an hour, tops).
posted by chocolatepeanutbuttercup at 6:51 PM on September 10, 2011

Best answer: Sounds like you have an issue with wet surface. Do you have another bathroom to use for a few days to shower with?

You need a few days to dry before the paint and a few days to dry after the paint. You've done some great things to try and help it dry, but Sheetrock is permeable and like a sponge, will soak in moisture even though it still seems dry.

You may want to find paint that's made for the bathroom rather than regular room paint. I remember ther was a special paint that required 36-48 hours to dry, but it was completely waterproof when it was dry. I'm sorry that I don't remember what the paint is called, but I'm sure you can find someone at Lowes or Home Depot who might be able to tell you what it is.
posted by Yellow at 8:03 PM on September 10, 2011

I recently addressed a section of wall above my shower that was getting mildewy--along with moving my shower curtain, which left anchor holes. The really helpful guy at the big box hardware store told me what to do:

Scrape, spray with a spray primer, spackle, sand, Kilz, paintable caulk (where the tub surround meets the wall) and then paint. I asked him if I could do everything except the painting (because I hadn't chosen a color/only had one day off work). He said absolutely not; I had to see it through to the painting so that everything would be sealed.

I suggest you scrape the old spackle out of the wall where the hooks were and start fresh. Or cut a larger hole and patch it up properly.

It took a lot of days of not showering to get everything done--letting everything dry between coats.

Looks nice now, though!
posted by vitabellosi at 9:44 PM on September 10, 2011

Response by poster: Just a final note to close the question...

I cleaned the wall thoroughly, dried it for four days, and... The primer stuck!

Thanks to all who responded.
posted by pla at 1:09 PM on October 10, 2011

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