Preparing a Wall for Paint

Surface Prep Make sure the surface is ready to paint.

The most important step in a successful paint job comes before you ever pick up a brush. The surface you are painting must be clean for your paint to adhere properly. Remove dirt and grease on interior walls with products like TSP or Soilax.
Once you have a clean surface, it is time to fill in any cracks or holes in the wall. Spackling will repair most surface damage. Apply in thin layers with a putty knife and taper the patch to blend in with the wall. For large holes or cracks, apply multiple thin layers, allowing each layer to dry before applying the next one. Allow plenty of time for the spackling to dry, then lightly sand the patched area so it is as smooth as the rest of the surface. Use a tack cloth to remove any dust from the sanding.
Primers When do I need a Primer?

Primers are an important and often overlooked part of the painting process. A Primer seals a surface so that your paint will go on evenly and adhere properly. Here are a few situations when a primer should be used:

New, Unpainted Surfaces - Any unfinished wood or drywall should be primed before it is painted for the first time. The primer will seal the surface and give the paint a good bonding surface. If you do not prime, you will use many more coats of paint and your finish may be poor if the paint penetrates the surface unevenly. It is much cheaper to apply a coat of primer than an extra coat of paint.

Patched Areas - If you applied spackling or other patching material, you should prime the area before painting. If you do not prime, the paint will not penetrate the patched surface the same way as the other surface and you will have an uneven finish.

Stained Areas - If you are painting an area with a water stain or other unidentified stain, a primer will seal the stain and prevent it from bleeding through the new paint finish.

Old Painted Surfaces - If you don't know what kind of paint you are covering, or if you applying a latex paint over an oil base finish, it is safer to use a primer than to just paint over the top. Some paints are not compatible and might peel if one is applied over the other. A primer will bond to your old surface and provide a safe surface to cover with your new coat of paint.

Dark Colors - If you are making a drastic color change or using a very dark color for your new paint, a tinted primer will help cover the surface with fewer coats of finish paint.