How to Seal Chalky Exterior Paint

Chalking refers to oxidization and breakdown of an exterior painted surface. It is more common with poor-quality latex paint and alkyd or oil-based paint, and you'll see it primarily on the sunny side of the house. Aluminum siding finish commonly chalks. Run your hand over the siding; if powdery white residue comes off, this needs to be completely removed prior to painting because water-based paint won't adhere to a chalky surface. If removing chalking is impractical, you must use a solvent-based primer to seal the chalking before painting.

Scrub brush
Power washer
Hose
Oil-based primer
Exterior acrylic paint

Instructions

- 1
  Scrub or power-wash as much chalk as possible from the siding. Rinse the siding thoroughly, and allow it to dry for at least two days.
- 2
  Seal the chalky surface with a coat of alkyd or oil-based exterior primer. Choose primer suitable for the type of surface -- an alkyd primer designed for painting chalky exterior paint on redwood siding is not necessarily the best choice for aluminum siding.
- 3
  Allow the primer to dry for between eight and 24 hours or as indicated by the product label. Drying time is affected by temperature and humidity, so it may take even longer in cool, damp conditions.
- 4
  Paint the surface with two coats of 100 percent acrylic exterior paint.

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