Primers are specially formulated to seal the wood, adhere well and form a smooth consistent base for the paint. Don’t buy a cheap primer. To make sure it’s compatible with the topcoats, buy the same brand as the paint you select. You don’t have to apply a primer over old sound paint unless the old paint is chalking or eroding badly.
When painting natural wood siding, use a stain-blocking primer on knots to prevent chemicals in the wood from bleeding through. Consider tinting your primer if you’ll be applying a darker color paint.
A good caulking job ensures that the topcoat will last for years and look good. It plugs the cracks where water can seep in and lift the paint. And it smooths over ugly gaps that make your home look shabby, no matter how well painted. Caulk siding gaps as well as around doors, windows, decks and other places where water or wind-driven rain could penetrate the walls and rot the framing. Apply caulk after your primer has dried and just before applying the topcoats.
- Spot prime knots with a stain-blocking primer or shellac. Shellac dries fast, but don’t use it as an overall primer since it won’t let the wood breathe.
- Apply an oil or latex primer to all bare wood. Using a roller or sprayer will speed application, but work the primer in with a brush to ensure good coverage and adhesion.
- Squeeze a smooth, even ribbon of caulk over the joint, completely covering it. Squeeze steadily, resting the tip of the tube on the wood and dragging it along at an even rate.Work primer as far into cracks as possible to waterproof the wood and provide a good adhesive surface for caulk you’ll apply.
- Apply a water-repellent preservative to wood that’s likely to get wet often. The wood must be dry for good absorption.
- Press foam backer rod into gaps larger than a pencil width using a putty knife or other blunt tool. Buy several sizes to accommodate different-size gaps.
Lightly press caulk against both sides of the joint with a moist finger. Then wipe away excess with a damp cloth. Don’t caulk horizontal joints; your walls need cracks to breathe.
Although there are dozens on hardware store shelves, you need only two for your home’s exterior. Acrylic or acrylic latex caulk is a good all-purpose caulk. It’s water based, cleans up easily and dries quickly, so you can paint over it almost immediately. Silicone acrylic is more flexible, but be sure the label states it’s paintable. Polyurethane is a good choice when you want extra strong adhesion. It outperforms acrylic but is stickier and harder to apply. Use it on stucco, masonry and other areas especially vulnerable to water.