Drywall primer/surfacers are the first step in getting the perfect paint job.
Most new drywall has three coats of joint compound on corners and seams, but much of the drywall’s paper face is left uncoated. This is a Level 4 finish as specified by the National Gypsum Association. Even though the walls and ceilings look and feel smooth to the touch, the drywall’s paper surface and joint compound have different porosities. This means that when the wall is painted, the seams look darker and have a slightly glossier finish. The condition is worse when there’s raking light and when walls are painted with dark or glossy paints. Known as joint telegraphing, it’s a problem I’ve seen a lot in the 20 years I’ve been a painter. One common way to prevent telegraphing is to go the extra step to what the National Gypsum Association calls a Level 5 finish, which has traditionally been done by skim coating the entire drywall surface with compound. However, by using a modern drywall primer/surfacer, a crew of three or four painters can prep and spray the walls and ceilings of an entire average-size house to a Level 5 finish in one day for less cost.
Choose the right product
You may have learned that PVA primer is the right primer for new drywall. Primer/surfacers are similar and include the same vinyl acrylic base that seals the drywall paper and compound. But primer/surfacers cover better because they have a greater percentage of solid particles than PVA primer. These solids create a uniform surface that reflects light evenly. There are two basic types of primer/surfacers: standard and high-build. The difference is in how thick they go on.
For less-demanding applications, such as under flat or nearly flat paint and on surfaces that won’t get raking light, I use standard products that apply in a coat of about 4 or 5 mils. These primer/surfacers have fewer solids (more than 40% by weight) than high-build products but still more than a run-of-the-mill PVA primer, which can contain as little as 30% solids by weight. My favorites in this class include PPG Speedhide Interior Max Prime and Sherwin-Williams Builders Solution Interior Primer/Surfacer. These products won’t produce a Level 5 finish, but they do a good job when applied over Level 4 finished drywall, and they can prevent joint telegraphing in many cases. Besides being less expensive than high-build versions (6¢ per sq. ft. vs. 13¢ per sq. ft.), these less-viscous primer/surfacers can be sprayed with less-powerful sprayers because they require a smaller tip (0.015 in. dia. to 0.021 in. dia.). Sprayers this size are lighter and less expensive than the spray rigs needed for high-build primer/surfacers, which require larger tips (0.023 in. dia. to 0.031 in. dia.). you also can roll on standard primer/surfacers with a 3⁄8-in. to 3⁄4-in. nap roller, but rollers only make sense for small jobs because spraying is much faster.
High-build primer/surfacers can contain 66% solids by weight, and they go on thick, around 20 or 25 mils wet, which is equivalent to four or five coats of regular paint. These products can fill sanding scratches, smooth drywall fuzz, and hide other small surface imperfections. For high-build primer/surfacers, I like PPG Speedhide MaxBuild and Sherwin-Williams High Build Interior Latex Primer. When applied over Level 4 drywall, these high-build products provide a Level 5 finish, which I prefer under dark or glossy paint and in harsh lighting conditions.