Should you prime a wall that is already painted?

I get this question all the time from a lot of people and today were going to discuss whether or not to use primer. Below you will see a short list when primer is necessary to achieve a good job.

You should prime a wall only on the following cases:

-      If the drywall has never been painted in other words if it’s brand new.

-     For walls that have a oil base paint, because latex paint doesn’t adhere very well to oil paint, now keep in mind that regardless of the job you should always sand the walls with a 100 grit sand paper before you paint or prime any wall, so that the new paint has a good grip over the old paint.

-    For stains on the wall due to water damage, markers or any other kind of stain. For water damage I recommend using either oil base primer or shellac primer (alcohol base), because sometimes if you use the latex primer you would see the stain come back again.

-     If you are painting bare wood, it is always necessary to prime bare wood because you want to make sure that the paint is going to stick well to the wood and also to cover the grains on the wood.

-     If you are painting a surface that is too shiny or smooth, because paint doesn’t adhere too well to shiny and smooth surfaces.

There is no need to prime a wall if they were previously painted, because basically the old paint is your primer, now if you have any of the situations I listed above then, yes! you need to prime the wall before painting.