Finish, protect wood siding

Wood must be properly finished with a paint, stain, or clear sealer. Left unprotected, it’s susceptible to rot and decay caused by moisture. Of special concern is the fact that wood expands and contracts with normal changes in humidity and temperature. These fluctuations may cause paint finishes to chip and crack, and over time puts stress on caulked seams around windows, doors, and at corners. If the caulk separates and fails to keep out moisture, wood rot may develop. Even species of wood that have a natural resistance to rot, such as redwood, cypress, and cedar, may decay if not properly protected from the elements.

Paint comes in unlimited colors and can be changed at any time. A house with wood siding must be repainted at least every five years, or as soon as the paint finish begins to deteriorate. A DIY paint job requires about 60 hours of labor. A professional crew will paint a two-story, 2,300 sq. ft. house for $3,000-$5,000.

Stain is a good choice for wood because it allows the beauty of the grain to show through. Stain penetrates wood fibers and helps seal them against moisture; it’s also resistant to the cracking and chipping that affects paint. Because stain is a penetrating sealer—not a coating, like paint—it’s difficult to change the color of previously stained wood. Staining a house is less labor-intensive than painting because prep work is minimal. Expect to pay $2,000-$4,000 for a pro crew to stain a two-story, 2,300-sq. ft. house. Using a rented paint sprayer, a two-person DIY team can re-stain a two-story house in 4-5 days for about $500, including the stain.

Clear sealers prevent moisture damage and allow wood to retain its natural color, but they must be reapplied at least every two years. Clear sealers are formulated to help slow the process that allows ultraviolet light to turn wood silvery gray. However, all natural wood, regardless of species, eventually turns gray when exposed to years of sunlight. Using a rented paint sprayer, a two-person DIY team can refinish a two-story, 2,300 sq. ft. house in a 3-day weekend for about $500, including the finish.

Clean stains on wood siding

Dirt is the most common cause of discoloration on wood siding. Clean annually using warm, soapy water and a soft-bristled brush. Divide your house into 20-foot sections, clean each section from top to bottom and rinse before moving on.

Mildew appears as black spotty stains. Clean the area with a solution of one part bleach to four parts water. Wear eye protection and protect plants from splashes. Rinse thoroughly with clean water.

Rust stains often appear as dark black splotches and vertical streaks. They’re usually caused by a metal fastener, such as a nail or screw, that wasn’t galvanized. Contact with moisture causes the fastener to oxidize, leaving streaks. To remove the stain, dissolve 4 oz. oxalic acid (available at hardware stores and home improvement centers) in 1 cup warm water. 

Wear eye protection and acid-proof gloves; avoid splashing the mixture onto adjacent surfaces. Apply the mixture to the stain and gently scrub with a soft bristle brush. Rinse thoroughly with water. Refinish the spot if necessary. Problem nails must be replaced with a galvanized or stainless steel fasteners.

Restore the color of natural wood siding

Siding that has discolored with age can be restored to its original color by applying a wood cleaner or brightener. These products often are intended for use on wood decks, but they work well on natural wood siding. They’re available at hardware stores and home improvement centers. Follow the manufacturer’s instructions.

Replace wood siding

Replace wood siding that show signs of damage. The most common damage comes from accidentally hitting the siding with sticks and stones thrown from a lawn mower, or from objects, like baseballs. Occasionally, wood siding may crack due to changes in atmospheric moisture. Repairs to wood siding require the expertise to remove the damaged siding while leaving surrounding siding intact. Unless you have the skills, hire a professional carpenter or siding contractor. Expect to pay $200-$300 to replace one or two damaged siding panels.

Prevent damage to wood siding

A house with wood siding is most vulnerable to water infiltration where siding butts against windows, doors, and corner moldings, says Frank Lesh, a professional house inspector in Chicago and past president of the American Society of Home Inspectors. Look for caulk that has cracked due to age, or has pulled away from adjacent surfaces, leaving gaps. Reapply a color-matched exterior caulk during dry days with temperatures in excess of 65 degrees F.

Lesh also stresses that no bush, tree branches, or shrubbery be allowed to touch the house siding. Foliage conducts moisture that can find its way into cracks and tiny openings in siding. “You should have enough room to comfortably walk between your house and any plant materials,” he says.