Thorough surface preparation can add years to the life of the paint job. Here’s what you need to do (or insist that the contractor do) before brush hits siding:

Protect the perimeter

Tie back shrubs and tree limbs. Cover plantings, air conditioners, and exhaust vents with drop cloths.

Scrub and wash

Dirt, mildew, and chalky old paint will prevent fresh paint or stain from adhering properly. Scrub the surface using a wire brush and a detergent such as Red Devil TSP Free to eliminate dirt. Use a chlorine bleach solution (one part bleach to three parts water) or a commercial cleaner for mildew.

A power washer rented from the hardware store or home center makes the job go much faster. Be sure to give the siding several days to dry thoroughly after power washing; if you don’t, the new paint may not adhere properly. Moisture migrating from behind the siding can cause the paint to blister.

Caulk and prime

Scrape away dried and cracked caulk around windows, doors, and trim. Apply fresh caulk where needed. If you’re painting the house, prime any bare wood exposed during scrubbing and scraping; use the brand of primer recommended by the paint manufacturer.

Scrape, sand

Use a hand scraper, a power sander, or a power washer to remove all traces of peeling and cracked paint. Scrape out rotted areas on windowsills and other trim, then fill with a wood filler and sand the wood smooth to hide the patch.

Read our complete Ratings report and related information on exterior paints & stains.