Yes, definitely. all new walls or ceilings need to be primed, using for eg. the pva primer. depends from a kind of surface, its condition and its absorptivity, the pva have to be diluted in the right proportion; water - pva. then only after when surface is dry we can paint first coat of the paint. to achieve a positive primed effect we have to ensure that the diluted pva is in right proportion with the water. if is not diluted enough then it will not penetrate the surface on a proper deep as should and will only make a thin coat like a foil. that is unwanted effect. the primer has to penetrate the surface in order to make it stronger and isolate its imperfections in the form of discoloration, oily stains, rusty metal residues or other material fraction, which its surface differs from the rest. after the primer application we have a clean and homogeneous surface, ready to make our painting job clean and tidy.