Do You Need Primer Before Painting?

Not always. Benjamin Moore says that if you are working with a previously painted surface that is in good condition, you most likely do not need to prime. The same page lists the cases where it highly recommends a primer: bare surfaces that have never been painted, bare PVC or composite material, surfaces sanded down to the bare substrate because of damage, rust or stains, dramatic color changes, and hard-to-coat surfaces such as high-gloss ones.

When primer is called for: new drywall and patches

Benjamin Moore’s list starts with bare substrates that have not been previously painted or coated. For new drywall, Sherwin-Williams’s steps are to tape and fill all panel joints, and, when the joint cement or patching material is thoroughly dry, to sand smooth, wipe away dust, then prime. Behr, in an article for professional painters, says that with drywall you will see sheen differences at the joint line if you don’t prime. Behr says porous surfaces, like stucco, will soak up too much paint, which makes priming the most efficient and economical choice.

Repairs on a painted wall get the same treatment. For previously painted surfaces, Sherwin-Williams says to patch holes and cracks, let the patch dry, sand smooth, and prime all bare areas before the topcoat. Benjamin Moore lists surfaces that have been sanded down to the bare substrate because of damage among the cases for primer.

Stains, glossy surfaces, and big color changes

Three more cases are on Benjamin Moore’s list: surfaces where rust or stains are present, dramatic color changes, and hard-to-coat substrates like plastic, laminate, glass, and high-gloss or non-porous surfaces.

For stains, Sherwin-Williams’s tip is to seal them with one of its primer/sealers, and it names water, smoke, ink, pencil, and grease stains. Benjamin Moore says alkyd, or oil-based, primers offer superior stain blocking, and gives tannin-rich woods, rust, smoke, and water stains as examples. Behr says some of its higher paint lines are designed to block a stain on a wall, such as lipstick, and that with a more economical product you might want to spot prime the stain.

Sherwin-Williams says to lightly sand glossy or nonporous surfaces to a dull finish, or use an abrasive cleanser. Benjamin Moore recommends a bonding primer for non-porous surfaces where sanding is not possible, and for previously painted surfaces with a high-gloss coating.

Bare wood

Sherwin-Williams’s steps for bare wood include priming all bare wood and patched areas. Benjamin Moore says alkyd-based primers are a good choice for both interior and exterior bare wood, and that they are efficient in penetrating the wood’s porous surface. Behr says a blocking primer is best for wood, especially redwood, cedar, teak, and mahogany, to avoid tannin bleed.

When paint-and-primer in one may be enough

Benjamin Moore says priming is not always necessary, especially as many of its paint products are self-priming, which it glosses as paint and primer in one. The case it gives for skipping primer is the one at the top of this page: a previously painted surface in good condition.

Behr says paint and primer products are generally most effective when refreshing previously painted surfaces that are in good condition, particularly for interior spaces.

Benjamin Moore’s statement is about its own products, and the same page still recommends primer for the cases listed above. Before you skip primer with another brand, check what its maker says about the product you bought.

How much primer to buy

This site’s Paint Calculator does not include primer. To work out primer with it, open More options and replace the coverage per gallon with the figure on the primer can; the calculator accepts 250 to 450 sq ft per gallon. Set Coats to the number of coats the primer can calls for. This page gives no general coverage number for primer. Use the one on the can.

Homes built before 1978: lead

EPA says any renovation, repair, or painting project in a pre-1978 home that has lead-based paint can easily create dangerous lead dust. It says that if your home was built before 1978, it may have lead-based paint, and that the older the home, the more likely it does.

EPA recommends hiring a certified lead inspector or lead risk assessor to test your home and determine whether the surfaces you are renovating have lead-based paint. It also recommends that homeowners hire a lead-safe certified contractor for these projects in pre-1978 homes.

On the rule itself, EPA says that, generally speaking, the Renovation, Repair and Painting (RRP) Rule does not apply to homeowners doing these projects in their own home. It does apply, EPA says, if you rent out all or part of your home, operate a child care center in it, or buy, renovate, and sell homes for profit. If you do the work yourself, EPA says to use lead-safe work practices, which its page describes step by step.