Do you need to sand before painting?

[#1]

The preparation needed really depends on the condition of your existing paint. If you don't have a stable surface to paint over, then you'll end up with a poor result. If paint is beginning to split, crack and curl, it will need to be sanded. - Jason

Remember you do not need to remove all of the paint, just the damaged and flaking portions of it.

Any paint that can just be peeled off needs to be removed as it is not bonded to the underlying layers sufficiently. If you can feel the edge of the paint with your finger and it has a thickness to it then use you will notice the transitions after applying additional coats of paint. If you can't remove all the paint then I would certainly sand those transitions to minimise them showing through after recoating.

120 grit sandpaper will remove material faster but 180 grit will leave fewer visible scratch marks in the timber/coating. If you were to only apply a topcoat over the sanded areas then I would suggest 180 grit or even 240 grit so the sanding marks don't show through it. But if you are going to undercoat before the topcoat, 120 grit should be fine. An undercoat is usually recommended once any flaking paint is removed and sanded smooth as it will seal and bind the rest of the existing paint. - MitchellMc

[CSParnell]

Using a scotch brite is also a good way to scuff the surface without clogging like sand paper.

 

[MitchellMc]

@CSParnell,

Scotch-Brite is also perfect for prepping old powdery Colorbond steel. You know how you'll see a garage door, and the paint is all white and oxidized? If you run your finger over it, it leaves a white residue. You can scrub it down with Sugar Soap and then scuff the surface with a medium/heavy-duty Scotch-Brite pad. It's then ready for a self-priming topcoat.

Mitchell

[CSParnell]

Hey @MitchellMc  yep I also used to use on prep with cars from a automotive paint supplier you can get different grades.

[mich1972]

Sorry to ask a silly question , what’s the best sandpaper to use once you have filled in cracks in the wall ? 

[EricL]

Hi @mich1972 

It's perfectly ok to ask these questions. I recommend using Flexovit 115mm x 1m 240 Grit Painted Surface Sandpaper Roll in combination with Paint Partner Cork Sanding Block. The sanding block guarantees a smooth flat finish when used with the 240-grit sandpaper.

If you have any other questions, please let me know.

Eric

[mich1972]

@EricL  I bought these products after work today. 
no more gaps for the cracks between the ceiling and wall and this sandpaper to rub down ? I still need to buy a scraper for the gap filling 

 

[EricL]

Hi @mich1972 

If you can avail yourself of the 240 grit that would give you a better finish than the 120 grit. The 120 grit is usually used for paint stripping due to the large particles on its surface, whereas the 240 has a smaller uniform surface that provides a nice even finish.

Eric

[mich1972]

@EricL  Thank you. I bought the 240 as you suggested after work today. Think I have everything I need to start now. 😀

[MitchellMc]

Keep us updated, @mich1972! I can't wait to see your results.

Remember to wet your finger with some soapy water and smooth off the gap filler. You can get some really nice results this way.

Mitchell

[mich1972]

@MitchellMc Thank you !!! I’m glad you mentioned it as I had to finish the shower floor with the silicone. AMAZING !!! Great handy tips for a beginner like me. 😄

[missedout]

That was very helpful information, thank you. missedout.