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We are repainting a number of rooms in our home, do we need to put primer over the existing paint?

Are there any other gotchas that we need to prepare for before repainting the walls?

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6 Answers

up vote 18 down vote accepted

No, in general, you don't need to prime existing paint.

To prepare for repainting:

  • wash the wall to remove any grease.
  • fill any holes and cracks with suitable filler, possibly using flexible filler for cracks.
  • sand and prime the filled areas - priming will seal the filler and keep it in place. You might want to sand and reprime the whole wall to avoid a patchy look.
  • repaint the wall with at least two coats of your new colour.

If the cracks are large you might want to check there's no current problem. New houses will settle quite a bit when first built and there'll even be some movement in older homes.

If you are painting over a dark colour with a light colour you might need more than 2 coats to stop the previous colour showing through. If that's the case then using a primer or basic white matt emulsion for the first coat (or two if it's really dark) is a more cost effective option than using the more expensive coloured paint for all the coats. Unfortunately you don't always find that out in time.

Paint in full daylight - especially for the final coat - so you can see where you've been and be methodical.

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I've found that priming can also help when going from dark to light colored paint. –  Niall C. Aug 21 '10 at 17:08
    
@Niall C. True - it's an extra layer of cheaper paint that'll help cover the dark paint up. I'll update the answer. –  ChrisF Aug 21 '10 at 17:09
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If you fill holes/repair cracks, it's a good idea to prime the entire wall (not just patches). If you only prime the patched areas, you could end up with a splotchy looking finish. –  Tester101 Feb 8 '12 at 17:16
    
@Tester101 there is that. –  ChrisF Feb 8 '12 at 17:29
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A tinted primer when going from light to dark paint also seems to help. We put a thick forest green type color over a pale yellow in two rooms. The first was just painted over, took 4 coats! The second with a tinted primer coat took just 2 coats of paint. –  Steve Jackson Feb 8 '12 at 18:29
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Priming is best. If you have to do two coats of paint to cover the old color, why not use a good primer or primer/sealer and one coat of a good paint? Most people will say otherwise, but primer will stick to old paint a lot better than new paint will.

I recommend wiping the walls down with a damp cloth first, but it's a lot of work, and I've never done it to a wall that wasnt't obviously filthy.

Use one coat of primer and one coat of paint.

Never ask a paint to do a primer's job!

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The problem is that one coat of the good paint may not be enough: the primer may shine through. –  Vebjorn Ljosa Aug 23 '10 at 18:26
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Perhaps. Primer is usually clear or white. If it's white, a light color shouldn't give you any trouble. If the paint is decent, a dark color should be able to cover it as well. I guess the success depends on the paint color and quality. Worst-case, you need a second coat of paint- but many times, you won't. –  nstenz Aug 24 '10 at 20:32
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If you want a really nice job, get a drywall pole sander and give the wall a quick going over with 200-250 grit paper before priming, and before your final colour coat.

Remember to wipe with a damp rag (use the pole sander if you like) before applying any paint/primer.

Drywall pole sander

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You can mix some of your paint with the primer to tint it to the final color hue. This has always worked for me. This is a good method if the paint change is a drastic one.

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In fact, you can get you primer tinted the same as your paint. –  Matthew Feb 23 '13 at 23:52
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There's one tip that was completely missed, and should have been at the start:

When painting over a surface that has had to be repaired or was very dirty (scrub it clean first), get both the paint and the primer tinted to the same color. As long as you buy the paint/primer in the same brand and they are both the same base, you will have exact match.

This one tiny little tip guarantees a perfect job with only one coat of primer and one coat of paint.

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At Home Depot I always have them tint the primer the same color as the paint. They do that at no cost. Also after caulking or drywall repair is dry I paint those areas with one coat of paint or primer before starting on trim cut in work . When I paint body .It is dry. The paint is always blotchy if those areas haven't had an extra coat.

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