Paint Sagging at 52% Humidity & 72 F

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Old 12-04-16, 03:46 PM
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Unhappy Paint Sagging at 52% Humidity & 72 F

We been having issues with paint sagging in our new house and have read everything we can to try to fix the issue. We've prepared the walls by cleaning with TSP and light sanding. We are currently painting primer on the wall at 52% humidity and at 72 degrees. Just to make sure the humidity is perfect, we have had a dehumidifier working in the room for the past few days keeping the humidity at 50% during the entire time. Some but not a lot of water has come out of the air. We have let the previous coat dry for a few days now.

Walls were previously painted about 5 years ago with Dutch Boy latex paint. We are painting with latex primer. We are using good Purdy brushes and the correct ply of professional quality roller. We are painting thin, even coats and sanding between coats. Would there be anything else causing paint sagging that we have not already tried to fix?

We have both painted successfully in the past doing less to the walls than we have done for this project so don't know what else to do.
 
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Old 12-04-16, 03:51 PM
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If you mixed the tsp too strong or did not rinse the wall afterwards adequately, the slippery residue that is left on the wall mixes with the paint and can affect the adhesion.
 
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Old 12-04-16, 04:21 PM
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We did rinse the tsp and used the directed amount for cleaning walls.
 
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Old 12-04-16, 04:35 PM
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What nap roller are you using?
Where's it running?
Middle of the wall, corners, near the top?
 
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Old 12-04-16, 04:41 PM
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3/8" nap as directed by the primer as well as a thinner sponge roller specifically for trim. It runs everywhere we paint - trim, walls, etc.
 
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Old 12-04-16, 04:52 PM
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What brand/type of primer are you using?
 
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Old 12-04-16, 04:58 PM
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We are using Kilz 2 Latex.
 
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Old 12-04-16, 05:00 PM
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#1, Why are you priming?
You did not back brush after rolling the trim?
No one here agrees with me but I also use a foam roller to get the paint on the trim as fast as possible but alway back brush it out to level it out.
I use a 2-1/2" Purdy or Wooster sash brush.
 
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Old 12-04-16, 05:02 PM
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I should have known. Worst primer ever. You need to apply the paint as thin as possible and backroll it after rolling it on. You did stir it, right?
 
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Old 12-04-16, 05:09 PM
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We are priming because the paint used before was extremely dark and old - from 5 years ago.
If we go over the surface already painted, it rolls away from the surface (glue-like look) and then sags. If we just leave it without going over it again, it doesn't roll up but sags after a short time.
 
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Old 12-04-16, 05:09 PM
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Kilz is like painting with milk.
Use Zinsser 123 instead.
Once again why does it need to be primed?
New wood, lots of repairs, drastic change in color?
 
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Old 12-04-16, 05:12 PM
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I'm guessing you did not sand and clean again before trying to prime.
No sanding, no tooth for the paint to cling to.
 
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Old 12-04-16, 05:22 PM
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We've had this issue with every paint project we've done in this house with everything from the highest priced Sherwin Williams paints to medium quality Sherwin Williams Ovation. This is the first time it's happened to us at the primer phase. We had to call professionals before to fix it the last time and they had the same issues - they were just able to hide it better than us.
 
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Old 12-04-16, 05:31 PM
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Did you test the existing paint to determine if it was oil or latex? I imagine latex would want to run if applied over oil based paint.
 
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Old 12-04-16, 05:37 PM
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The old owners left us the paint they were using, so we can confirm it's definitely latex.
 

Last edited by brightface77; 12-04-16 at 05:53 PM.
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Old 12-05-16, 02:46 AM
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It can only be one of three things; application error, contaminates on the substrate or a defect in the paint.
[or a combination of them]

As stated above not rinsing the TSP well enough will cause adhesion issues. I normally only use TSP on the exterior were I can rinse well with a hose or pressure washer. I never use Kilz2 because it's a poor stain hiding primer and it's reported to have adhesion issues. If you scratch the primer does it stay stuck or does it start to peel?

I assume the reason the painters were able to get satisfactory results is because they kept back rolling as needed to wipe up all the runs. I've painted in all humidity levels and the entire range of acceptable temps and never ran into any applications issues that couldn't be dealt with.

Is the existing wall paint latex enamel or flat latex?
 
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