I have done repainting my wall for at least 4 to 5 times but the problem persist as below, what could be the possible root cause and are there any remedies for it?



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Did you do a sealer coat before colour paint?
Your pic seems to fit the "lap marks" issue - https://www.benjaminmoore.com/en-us/contrac...oting/lap-marks



This post has been edited by ceo684: Apr 15 2021, 12:38 AM

need to put oil based or shellac primer, the patches are basically like oil/chemical stains that were on the concrete which will "leak" through unprimed paint coat especially latex paint. Have to seal it with primer to prevent it from staining the color paint.

This post has been edited by DragonReine: Apr 15 2021, 12:15 AM

You need to prime it first.

i have a similar problem. but its for my outdoor wall. its a white gate pillar wall. the parts i just repainted over with the same paint has this black dirt markings.

does this mean i need to use primer too on the parts im gonna repaint ?

If it looks like watermarks from dirt dripping then its probably dirt..else random black dots will be algae/moss whereby you need some fungicide like nippon fungicide, apply and leave on for 24hrs to kill the fungi spores first and foremost.