Preparing Siding

This story covers cleaning siding and soffits, removing old paint and fixing cracks in wood siding.


No matter what kind of siding you have on your house, perform a general inspection before you prepare it for painting. Look for mold, mildew, damaged siding, and wet or dry rot.

Once you've inspected the siding, preparation follows the same general order -- remove mold and mildew, wash away dirt and chalking, repair or replace damaged siding, remove loose paint, and spot-prime the affected area.

To get the best finish on glossy surfaces, scuff sand them using a sanding block, pole sander, or sanding pads and 120- to 150-grit sandpaper. Do not oversand; just scuff the surface lightly to provide a roughened tooth for the new paint.

Water is the chief enemy of both wood and paint, so caulking gaps is important. Apply a top-quality all-acrylic or siliconized acrylic caulk to inside and outside corners, joints, seams, and other gaps where water could penetrate the wood's exterior. These caulks will adhere to a wide range of materials, even when they are wet.

Preparing wood siding: Step 1

Starting at the eaves and soffits, wash the surface with water only. Use a pressure washer equipped with a fan nozzle and adjust the pressure for cleaning wood surfaces. Do not hold the tip too close to the wood. A power washer can poke holes in wood and break windows.

Preparing wood siding: Step 2

Working from the top of the wall to the bottom, direct the water downward. Spraying head-on can damage the siding, and aiming the spray upward can drive water behind the siding and lift it from the wall. Turn the water off to release pressure before disconnecting the hoses.

Preparing wood siding: Step 3

Using a 5-in-1 tool or scraper held almost flat against the surface, scrape away loose paint down to the bare wood. To avoid gouging the surface, work parallel to the grain of the wood as much as possible. On carved millwork, use contoured scrapers available at your home center or paint store.

Preparing wood siding: Step 4

Using a 5-in-1 tool or stiff scraper, widen cracks to just under 1/4 inch. This will remove debris in the crack and create a recess for patching compound. Remove loose paint with 80-grit sandpaper and take up any dust with a brush and water-dampened rag.

Preparing wood siding: Step 5

Apply a thin layer of exterior patching compound to all scraped and cracked areas, feathering the compound to create a level surface. Allow the compound to dry thoroughly. If the compound shrinks, sand it lightly and apply another thin layer.

Preparing wood siding: Step 6

Sand patched areas with 100-grit sandpaper to make the compound level with the existing paint. This leveling process will help hide the repair when you apply the primer. Remove dust with a wide brush or damp cloth.

Preparing wood siding: Step 7

Apply an exterior stain-blocking primer on all repaired areas and all bare wood. This prevents wood tannins from discoloring the paint. On cedar, redwood, and mahogany, use an oil-base primer and apply it in dry weather at the recommended spread rate. Finish-coat the surface within a week.

Removing mildew: Step 1

Mask, cover, or otherwise protect plants, surfaces, or objects that could be damaged by the cleaning solution. Dampen grass, plants, and other vegetation with water. Wet the mildewed area with water using a pump sprayer, a garden hose, or a pressure washer.

Removing mildew: Step 2

Mix a cleaning solution of three parts water and one part household bleach in a pump sprayer and apply it liberally. Scrub the mildewed area with a stiff brush, reapplying the solution to keep the area wet for 20 minutes.

Removing mildew: Step 3

Using a pressure washer or hard spray from a garden hose, rinse the area thoroughly with water. Take up any protective coverings from adjacent surfaces and rinse vegetation with a light spray from the hose. Let the surface dry thoroughly.

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