How do I prepare an already painted wall for new paint?

Question

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?

Answer 1

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.

Answer 2

If you want a really nice job, get one of these Drywall Pole Sanders 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 (on the pole sander) before applying any paint/primer.

Answer 3

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!

Answer 4

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.