I am having a problem with paint not sticking.
I have a ceramic tiled tub surround with DensShield as the tile backer board. The backer board was extended beyond the area covered by tile abutting (perpendicular to) an aluminum window frame. This left an approx. 3" strip between the finished side of the exterior wall of the house and the start of the tile, which was painted. Within this strip the paint would “bubble” when the shower was used. Two days ago, I scraped off the old paint, coated a rusted screw head with Jasco Prep & Prime and filled a 3/16” deep by 1” diameter area around the screw head with Dap Presto Patch. Yesterday I sanded the Presto Patch and primed with Zinnser Bull’s Eye 1-2-3 primer. After about 6 hours, as I was applying all-purpose joint compound to a nearby (higher) area of wall, some splashed onto the primer coated area. As I cleaned up the splashed joint compound, the primer under the splash peeled right off. I am concerned that simply repainting will not be enough to avoid the same problem in the future.
Was this a matter of simply not letting the primer dry long enough or is there a sealer that I need to apply prior to the primer? (e.g. Can shellac be painted over?)
Here is what Georgia/Pacific (DensShield manufacturer) says about painting over the backer board:
Can I paint DensShield® tile backer outside the shower area in a typical residential bathroom wall installation?
Yes, the steps to accomplish this are quite simple. First, finish the joints using fiberglass mesh tape and setting type joint compound. Next, skim the entire DensShield panel surface with setting compound. Once this material dries out, prime and paint, or prime and paper. The use of setting type joint compounds are preferred over ready mix joint compounds near moist areas.
I’d like to find an alternative (and just as good) way to solve this problem. Although I have not checked yet, I’m guessing that the minimal amount of setting type joint compound I can buy nearby will be much more than needed for this small area.
The total “problem” area is less than 1 SF.
Any information/suggestions/solution you can provide will be much appreciated.