How to Prep Wood Siding for Repainting
Whether you have cedar clapboard, pine T1-11, or HardiePlank that mimics wood, the prep you put in determines whether the new paint job lasts 5 years or 15. This guide covers the sequence every US professional painter follows before the first brush hits the wall.
Wash with a mildewcide solution
Mix a 3:1 water-to-bleach solution with a cup of Jomax per gallon, or use a pre-mixed exterior house wash. Scrub siding with a soft brush on an extension pole, rinse with a garden hose (not pressure washer on old paint), and let dry 48-72 hours until the moisture meter reads under 15%.
Scrape and feather-sand loose paint
Use a carbide scraper to remove all loose or peeling paint. Feather the edges with 80-grit sandpaper so the transition between bare wood and remaining paint film is smooth - otherwise the repaint will telegraph the scraped outline. Wear a NIOSH-approved respirator on homes built before 1978 until a lead test has cleared the substrate.
Set nails and caulk gaps
Walk every elevation with a nail set and hammer - protruding nails will rust through paint within a season. Caulk all vertical trim-to-siding joints with a 50-year acrylic-urethane sealant. Skip horizontal laps (they need to breathe) unless they are caulked already.
Spot-prime bare wood
Every bare spot must be primed before the topcoat. Oil-based stain-blocking primer (Zinsser Cover Stain) is the gold standard on cedar and redwood to lock down tannin bleed-through. Acrylic primer is fine on pine and engineered wood. Do not rely on 'self-priming' topcoats for bare wood.
Mask and protect landscaping
Cover shrubs with breathable drop cloths - plastic will cook plants in US summer heat. Tape windows with 3M 2090 (14-day) blue tape and skirt the foundation with canvas runners. A tidy masking pass saves hours of cleanup and signals a professional job to HOA inspectors.
Put it into practice!
Use our simulator to apply these tips directly on your project photos.