ᐅ Grinding cement screed – Which grit size is recommended?

Hello everyone,

I started preparing our cement screed for a floor coating over the weekend. The screed was already quite smooth and mostly somewhat "shiny" from the construction side, but in some areas it is coarser and sandy (looks like cement residue). I began sanding with an orbital sander and 40-grit sandpaper. I immediately noticed that this cement residue is very easy to remove this way. However, when I sand the smooth areas, the screed surface actually becomes rougher instead of smoother.

My question is: Is it normal for the smooth screed areas to become rougher when sanded?

I have often read online about using 16-grit for initial sanding. Unfortunately, the coarsest grit available in the hardware stores here is P40.

Thank you very much.

Best regards

The smooth screed becomes too rough when grinding with P40, so you want to use P16 instead? Please explain.