I'm looking into repainting a classroom in an NGO facility (can seat about 80). Due to both time and budget constraints, I don't have freedom of spending too much time priming and painting the entire room. I suspect I can readily prime half the wall height and paint the whole room within the allocated time.
Would I create an odd mark on the wall if I only prime up to about head height? I plan to use a dry roller between the primer and bare walls to even out the edge so it doesn't get a sharp bump.
The rational for priming half the room is because the marks on the walls are all chest height and lower. I've already used a power sander and lightly sanded all the marked areas, and have sanded all repaired sections of the wall. I'll want to put primer on the repaired areas and the marked up areas to help with paint adhesion.
2020-09-01 Update: Wall material mixed. I can tell there is concrete and dry wall, with a layer of wall putty. Region is Hong Kong, which is typical to simply do Putty + Surface paint, skipping the primer. I know this doesn't work well and high humidity = putty failing, and paint peeling off.
Sanding wise, it is light sanding. It isn't past the paint layer. It is mainly to get the surface scuff marks off so the primer can attach better to the existing paint (instead of some random material). Any deep gouges are filled with wall putty and sanded flat.
If I had more time, I would sand past the paint and putty layer, and do a thicker sealer/primer layer onto the material. The current paint is not showing any major area failure, so I think it'll hold a repaint.