How should I finish removing wall texture and preparing for paint?

Question

I have a wall that needs a new paint job. I'm trying to make a call on how much prep work is needed before applying the paint. From the other questions it's not what would be the properties or a well prepared surface so am providing a real example.

The below table gives a comparison between the current state and a sanded state.

Original	Sanded

This was sanded manually with a 120grit paper roughly 15 seconds The 'roughness' is less than 1mm deep in both cases.

I'm trying to understand to what prep work is needed to reduce the risk that the new paint will peel or visible uneven. Am not looking for perfection form that close up just want to that it looks like an homogeneously painted wall when looking at it from half a meter or on a sunny day.

Some options that come to mind:

• sanding the old with an electrical sander all the way to the plaster
• applying drywall mud to fill the little gaps
• just sanding lightly with a finer sandpaper and applying a primer

What would classify the wall as paint ready and if it isn't, which steps preparation steps to choose?

Answer 1

Sanding is not an appropriate technique for painted walls. You never^* want to sand latex paint with the intent of grinding it off. That's not likely to go well as it leaves behind shredded paint and an uneven surface where the paint peels or melts.

You need to skim the wall with a topping compound using a wide knife (12" or wider), then sand lightly with a large pad or drywall screen to eliminate very minor imperfections. Do the whole wall, scraping gently with the knife between applications to remove crumbs and thin edges. Use a strong light at a low angle to examine, then repeat. You're done when you see no shadows.

Now prime the surface, and check it again with the light. Make additional skim repairs if needed and re-prime.

Now you're ready for paint.

---

^* Never say never. If you have, say, a pointy dab-and-pull type of texture it may make sense to grind off the peaks before you begin skimming. If you have something robust like plaster underneath softer texture you could feasibly grind that off with low-grit sandpaper, again before you start skimming. There's always skimming, though, even if you intend to retexture.