Can I Apply Latex Primer Without Removing Old Paint?

Surface Prep

• In most cases, you can apply a latex primer to a previous coat of latex or oil paint without struggling through any additional surface prep, although there are some important exceptions. If the old paint is peeling, if there are rust stains, if the previous coating is a high-gloss enamel, or if the previous coat contains lead, some additional surface prep may be appropriate.

Priming Over Peeling Paint

• Peeling paint is a sign of coatings failure, but it usually won't require removal. Instead, begin by gently scraping over the affected area with a wire brush to remove any loose chunks before applying a special peel-stopping latex primer. This type of undercoat has a high level of adhesive and will penetrate through the old, failing layer of paint and bond it back to the substrate. If the resulting surface is noticeably uneven, apply spackling compound or wood putty to the void areas and smooth with a putty knife. Follow up by spot priming the affected area.

Priming Over Glossy Paint

• Latex finish coats may not bond effectively to high gloss surfaces, especially if the previous coating was an oil or alkyd paint. Wash the old surface with a TSP or TSP substitute, rinse with water, and allow to dry before applying a low-VOC bonding primer. This type of latex primer will adhere firmly to the old paint, allowing you to follow up easily with your latex finish coat.

Priming Over Stained Walls

• At one time, alkyd primers were the preferred product for covering stains caused by tobacco smoke, grease, water spotting and smoke damage, but prodded by environmental regulations, a number of manufacturers now supply acrylic latex stain-killing primers. These low-odor alternatives cover and seal the stains, eliminating the risk of bleed-through on the finish coat.

Priming Over Corrosion

• When rusty nail heads bleed through indoors, or outdoor metal surfaces show some corrosive discoloration, the best approach is often as simple as using a stain-killing latex primer/sealer. But if the damage is more severe, a rust-inhibiting primer may be appropriate. The latex varieties are typically high-solid formulas with a high level of acrylic or urethane content, and they are suitable for spot application over the affected areas. Scrape off any corrosive buildup before applying the primer.

Test Older Surfaces for Lead Paint

• If your home was built before 1980, you should check for the presence of lead paint before you begin repainting. Pro-Lab lead testing kits are available at Home Depot, Lowe's, Menards and Ace Hardware stores. Their pro-grade kit lets you send them paint chips from your home for laboratory analysis. If lead paint is detected, you can choose between removing the old paint entirely or encapsulating it with a water-based barrier coat that will serve as a high-tech elastomeric primer.