Newly finished wallboard presents two distinctly different surfaces to be coated, the face paper of the wallboard over the untreated area of the wallboard, and the taping compound over the seams, corners, and fasteners, (screws or nails).
Paint applied to the face paper and the compound will be absorbed unequally and will exhibit problems such as "joint banding," a phenomenon that makes the paint appear shadowed, or darker, over the areas treated with compound.
Some drywall installers solve the porosity problem and prevent joint banding by applying a skim coat of drywall compound over the entire wall surface.
A lot of drywall contractors try to get around joint banding and also cover up poor workmanship by applying drywall texture, a very loose and powdery mixture that is little more than chalkand water. This creates a problem for the paint application, as paint does not adhere well to powdery chalk.
There is a simple, yet important step that can be taken to improve the quality of the texture. To make it less porous and adherent, one must improve its cohesive strength. This can be accomplished with the addition of a latex emulsion (resin) that is used in many latex interior paints as a binding agent. Normally to every 100 gallon batch of spray applied texture, add 5 gallons of Latex Emulsion. This additive "glues together" or binds the powdery particles tighter, thereby increasing its density, adhesion and cohesion to provide a more sound base for any latex paint.
Without this additive, you can expect great difficulties with the adhesion of wall coverings and paints to the drywall surface. Most national paint stores and drywall suppliers carry ready mixed Latex Emulsion additives.
When cured and dry the reinforced texture is firm and dust free providing a sound surface for your first coat of Latex Primer.
Wallboard with no texture:
If your wallboard has not been textured or it has been "skim coated",a latex primer is a must.
Primers seal the surface to equalize paint absorption, and minimize surface texture variations. A good quality latex finish paint such as a satin enamel will give you years of trouble free painted walls.
Note: If you are going to apply a heavy texture to new drywall ceilings you should always prime first with an OIL base primer to stop the wallboard from absorbing water from the texture resulting in sagging.