Joint compound to smooth old paint layers.
In the process of refinishing walls in a 1000 sf, 30 year old townhouse. Had to do a lot of patch work, from fitting 2x3 foot new drywall patches for big holes, to a gazillion nail pops and picture hanging holes.
The walls were also very textured from lots of bad paint jobs over the years from previous owners (latex). I discovered that using a drywall mesh sanding sheet on a sanding block dipped into a bucket of warm water, greatly speeded things up from dry sanding. It basically softened the paint a bit. While wet and with a lot of elbow grease, I was able to remove the top layer of old paint and smooth the walls down a lot, almost looks like new paint.
While patching broken corner beads on a small wall and blending the new joint compound area into the old, wet-sanded paint area, I discovered that I could very quickly skim a very, very thin layer of joint compound over the whole wall, scrape again immediately with the knife, and end up with the whole wall being almost texture free. With a very quick light sanding with fine sandpaper, the result is a wall that is almost perfectly smooth with virtually no texture at all and no discernible transition between drywall patches where the new drywall meets the older painted wall.
On the older painted part of the wall, there is basically just enough joint compound filling in the "troughs" of the orange peel texture of the sanded old paint. The "peaks" of the wall are the old clean, smooth, wet-sanded paint. This means that on the old painted wall, there is just the thinnest layer of joint compound in the depressed areas of the texture, not a complete skim coat of joint compound on the whole wall.
Getting to the question. Is this an acceptable thing to do? Is having just a tiny bit of joint compound filling in the light texture of the paint enough to bond with the old paint and accept latex primer? When I apply the primer, will this bond everything together and make a good base to accept new paint, or am I risking the very thin "filler" joint compound coming away from the previous latex. I figure it's like having an entire wall with the amount of joint compound you would have at the thinnest amounts found at the very edge of a patched area, after the edge of the patch has been sanded to feather into the old wall.
Scraping on a very thin layer of joint compound, then scraping immediately again with the knife back over the whole wall is actually very quick to do. I figure I could apply this technique to all the walls in the entire townhouse in a two or three days and end up with perfectly smooth walls with no evidence of any patching or mismatched areas of new dry wall patches next to old painted dry wall.
Is there a reason why I should not do this? I don't want to have fresh looking walls that look like first time painted new drywall, only to have the paint peal in a short time because the joint compound skim on the walls is super thin.
The joint compound I'm using is, "DAP Wallboard Joint Compound." It seems to be much smoother and have more "bonder" in it, for lack of a better word, than the generic stuff I got from HDepot, with the green lid.
Any thoughts or suggestions are much appreciated.
With the prep you've done, you might get away with it, but I wouldn't chance it. First use a bonding primer, Bullseye 123 or similar, then skimcoat, prime again, two topcoats....done deal.
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