How to Prep Walls for Painting
Preparing Walls for Paint
Nobody likes paint prep, but it's a must if you want your newly painted walls to be durable and look awesome. Paint doesn't bond well to dirty walls so the first step is to clean them if needed. Regular dish soap, or TSP, are both good options for removing grime from walls. Let the walls fully dry before doing any drywall repairs.
Sand the Walls
Always wear a respirator while sanding. A dust mask is fine too, but a respirator is better. Sanding dust is really bad for your lungs. Most paints contain silica particles, which can cause silicosis from long-term exposure.
To sand walls, use a sanding head equipped with 80 to 100-grit sandpaper. The sanding head screws onto the end of an extension pole for painting. Sand the walls from top to bottom to smooth out the surface.
Repair Holes and Cracks with Joint Compound
Use Easy Sand drywall compound (powder form) that comes in a bag. You can buy this product at any major home improvement store. I use the 20-minute version the most. The patches dry in twenty minutes for sanding. You'll need a mud pan to mix the compound with water.
Fill Nail and Screw Holes
Fill wall holes with joint compound, using a putty knife, or a taping knife. Larger holes from drywall anchors usually require two coats of compound to blend the patch in with the wall. Don't use spackle to patch holes. Spackle is too soft, shrinks, and takes too long to dry.
Repair Big Cracks with Drywall Tape
The best way to repair bigger cracks in drywall is with fiber glass drywall tape or paper tape. In my experience, paper drywall tape works better because the small holes in fiberglass tape allow the crack to reform again over time.
To permanently fix big cracks with drywall tape, lightly gouge the entire length of the crack with a taping knife to level it with the surface. Fill the crack with compound and place a piece of drywall tape directly over the crack, pressing down on the tape with your knife to squeeze out the excess compound underneath. Apply two to three coats of joint compound over the tape, sand, prime, and paint.
Prime Walls for Painting
Whether or not you need to use primer depends on different factors. There are many primer products that serve different purposes. Some serve as a bond coat, while others seal surfaces to prevent bleed-through from tough stains.
Are the walls painted with glossy, oil-based paint?
Latex paint doesn't bond well with oil-based paint or overly glossy walls, especially faux finish glaze. Oil paint is too hard, glossy, and latex paint is unable to penetrate the drywall underneath. As a result, paint rub-off can occur. A bonding primer must be used first before painting. A good product for this purpose is Extreme Bond Primer from Sherwin Williams.
Are there stains on the walls?
Most latex paints won't block wall stains from water, nicotine or permanent marker. The only way to prevent these stains from bleeding through the paint is by using an oil-based primer first. Shellac-based primer works great too. Kilz is good (oil, not latex), as well as ProBlock from Sherwin Williams, both of which are available in a spray can.
When the top layer of drywall tears open, the brown paper beneath can become exposed. This can happen when drywall anchors or bathroom fixtures are removed from walls. When the brown paper is exposed it needs to be primed first. Painting directly over the torn paper will almost always cause bubbles to form on the surface over it. A quick fix is to prime the torn areas with a spray can of the shellac-based primer BIN. The primer dries in less than thirty minutes.
Are you painting red over white?
To avoid having to paint multiple coats of red, white walls should always be primed with a tinted primer first. When painting red on white walls a grey tinted primer works best, tinted to the same shade as the red being used. The red paint will cover usually in no more than two coats over the prime coat. A good product for this is Multi-Purpose latex primer from Sherwin Williams.