Does AC Plywood need to be primed before skim coated
Long story short, I have a small 2×4 AC plywood that was skim coated, primed and then painted…
It’s been around 8 years and now it’s started to just crack and the paint/skimcoat JC is peeling right off the AC plywood.
I plan to just scrape it down to bare wood and refinish again…
Does plywood in general need to be primered before skim coated.
I am planning to use Zinnsers primer before skim coating this time around
Replies
Not much help on the primer/skim coat on the face of the ply.
But, where is this located? With the cracking almost sounds like there's movement of some sort in the ply causing the cracking. Was the backside primed or is there possibility of moisture behind it?
I think I would prime it for sure to help with the bond and use either Regular drywall compound (All Purpose) or Durabond (not Easysand) which has more "stick" than topping compound.
I suppose sometime or another I have blended in plywood to drywall.
Plywood is not really meant to be skim-coated because the expansion/contraction rates of plywood and joint compound are dissimilar. I don't know of any material that is intended for skim-coating plywood, I'm not even sure that wood filler would really work.
However, priming the plywood first will definitely increase chance of the skim coat adhering.
Probably better than priming would be to put on a layer of something like "wall liner". (In fact, put on the wall liner and you may not need to skim coat.) Of course, you should prime anyway, before putting on the wall liner.
Actually in my research, I think I will try wood filler.....and then primer/paint ontop. I will call Zinnsers today as I did not see it on their website but I thought they had a elastomeric type of primer as well.
The plywood is much smaller than I stated. Probably closer to 30" x 13" Deep. I can't really install 1/4" drywall or the like on top. The *front* of it is finished tile. It's the side framing for a basement window. The 3 sides (sides and bottom) is finished in tile. The top of this is the problmatic AC plywood. The basement does not see much moisture. It's more a ~mud room~ than a bathroom where showers are taken.
I'm thinking 2 coats of wood filler and then sand it smooth...
Ahh, the old "I want to
Ahh, the old "I want to finish plywood" problem.
First off, I suspect that simple moisture in the air has started to separate the plys in the plywood- hence the cracking. I'd say that you're best off replacing the plywood first. You'll want to seal all six sides of the new plywood.
Now ... how to prep the plywood? While the idea of a primer has some appeal, and even a skim coat of joint compound makes some sense .... I think we can do better.
(What follows is untried speculation)
First off, I'd use "Exterior" rated plywood (for the better glue), and I'd expose the rough side if I was going to apply a skim coat of joint compound to it.
Perhaps what you want is not 'primer,' but 'sanding sealer.' I've made a pretty decent sanding sealer by diluting Elmer's white glue 50/50 with water.
Maybe even ... after two coats of sanding sealer you can use a more dilute mix to glue a layr of butcher paper to the wood. That ought to make for a pretty close match to the texture of the drywall, and might even eliminate the need for a skim coat.
Since plywood these days is somewhat thinner than drywall of the same nominal size, maybe a visit to a flooring contractor is in order. They have a heavy paper they use for doing their layouts - it's actually the backing that's used for vinyl flooring. That paper ought to really match drywall for texture!
Remove and replace would be the my 1st inclination but it is the top of a *box* for the basement window. The finished/front side of it has tile in which the tile is partially affixed to the ~side~ of the plywood.
Thus I am needing to stick with what I have and attempt to reseal it at least and refinish and see how it stays....
Remove and replace would be the my 1st inclination but it is the top of a *box* for the basement window. The finished/front side of it has tile in which the tile is partially affixed to the ~side~ of the plywood.
Thus I am needing to stick with what I have and attempt to reseal it at least and refinish and see how it stays....
I'd paint it with an elastomeric paint such as Sherman Williams SherLastic or ConFlex XL because they can shrink and expand without cracking.
What you propose sounds reasonable. The only other suggestion I have is to cover it with some laminate (like formica).