How important is it to prime sheetrock before painting? What about if I am painting over existing paint?
Question:If it is possible to skip priming, I would like to. I am in a bit of a rush. But if it is really that important, I will do it.
Answers:
You definitely need to prime new sheetrock to seal the drywall and prepare it for paint. Sheetrock that is already painted generally doesn't need priming unless you are painting over a gloss finish or smoke and water damage.
I have painted new drywall without primer but it doesn't same time or money. The paint will work as primer sealing the surface. Then you will find that coverage is poor so you need to recoat with more paint. So the first coat acts as a sealer whether you use primer or paint. I always use primer/sealer now but often use lowest cost available. Then I put good quality paint over it. As for walls that already have paint, no I don't prime unless it is a major color change, like from dark to light color. Then primer can help.
Priming of new drywall is very important because you are doing two things. 1. Traping any loose particle left from sanding, and 2. Putting on a first coat at a very low cost compared to top coat paint. Remember, haste makes waste. Another reason to use different paints is that you will get all those particle trapped in the good paint and will show all over the wall, only making for more work.
the primer seals the drywall and allows you to use less paint wich will last longer
I would use a PVA primer for your Sheetrock and depending on the type of paint on your painted walls use Kilz ,either original for oil based and Kilz 2 for latex based, the reason for priming painted surfaces is to prevent the pigment from the old layer to interact with the new layer of paint giving a different hue to the color you are applying.
Prime it for sure. It seals it & the texture (if any) and prevents burning of the topcoat. If you are in a hurry you can use (2) coats of flat paint, although flat doesn't stand up to abuse very well. A good primer can be tinted to help you avoid applying (2) topcoats, if you are going for a color.
Painting over existing paint is acceptable, providing it is not glossy, nor does it have oxidation. Rub your hand over it, if it leaves a dust on your hand, you will need to prime it before painting. Also, if it is an older house & the paint is a true color(red, yellow, etc) prime it with an oil based primer. Otherwise it will come through the topcoat.
Before painting over the existing paint, make sure you clean the surface first. Mild soap & water will do a good job, if it is really dirty, clean it with TSP & water.
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