Aticle 4 of the Essential Maintenance Series

Cleaning and Caring for Siding

By: John Riha

Published: August 31, 2009

Cleaning and repairing your home's siding once every year will pay off in the form of a long life and increased value for your home.

Cleaning wood, vinyl, metal, stucco, brick, fiber-cement siding

All types of siding benefit from a good cleaning once every year to remove grit, grime, and mildew. The best way—whether you have wood, vinyl, metal, stucco, brick, or fiber-cement—is with a bucket of warm, soapy water (1/2 cup trisodium phosphate—TSP, available at grocery stores, hardware stores, and home improvement centers—dissolved in 1 gallon of water) and a soft-bristled brush attached to a long handle. Divide your house into 20-foot sections, clean each from top to bottom, and rinse. For two-story homes, you'll be using a ladder, so keep safety foremost.

Cleaning an average-sized house may take you and a friend every bit of a weekend. If you don't have the time—or the inclination—you can have your house professionally cleaned for $300-$500. A professional team will use a power washer and take less than a day.

You can rent a power washer to do the job yourself for about $75 per day, but beware if you don't have experience with the tool. Power washers force water through a nozzle at high pressure, resulting in water blasts that can strip paint, gouge softwoods, loosen caulk, and eat through mortar. Also, the tool can force water under horizontal lap joints, resulting in moisture accumulating behind the siding. A siding professional has the expertise to prevent water penetration at joints, seams around windows and doors, and electrical fixtures. 

Inspect for damage

Right before you clean is the ideal time to inspect your house for signs of damage or wear and tear. A house exterior 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. For all types of siding, 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 for maximum adhesion.

Other defects include wood siding with chipped or peeling paint, and cracked boards and trim. If you have a stucco exterior, be on the lookout for cracks and chips. For brick, look for crumbling mortar joints. Repair defects before cleaning. The sooner you make repairs, the better you protect your house from moisture infiltration that can lead to dry rot and mold forming inside your walls.

Repair wood, vinyl, and fiber-cement siding 

Damage to wood, vinyl, and fiber-cement horizontal lap siding often occurs because of everyday accidents—being struck by sticks and stones thrown from a lawn mower, or from objects like baseballs. Repairing horizontal lap siding requires 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 or pieces of wood clapboard.

Repaint wood, fiber-cement 

Houses with wood siding should be repainted every five years, or as soon as the paint finish begins to deteriorate. A professional crew will paint a two-story, 2,300 square foot house for $3,000-$5,000. If you've cleaned your house exterior yourself, you've done much of the prep work and will save the added cost that a painting contractor would charge to clean the siding before painting.

Fiber-cement siding, whether it comes with a factory-applied color finish or is conventionally painted, requires repainting far less often (every 8-10 years) than wood siding. That's because fiber-cement is dimensionally stable and, unlike wood, doesn't expand and contract with changes in humidity. 

It's a good idea to specify top-quality paint. Because only 15% to 20% of the total cost of repainting your house is for materials, using a top-quality paint will add only a nominal amount—about $200—to the job. However, the best paints will outperform "ordinary" paints by several years, saving you money.

Repair brick mortar, stop efflorescence

Crumbling and loose mortar should be removed with a cold chisel and repaired with fresh mortar—a process called repointing. An experienced do-it-yourselfer can repoint mortar joints between bricks, but the process is time-consuming. Depending on the size of the mortar joints (thinner joints are more difficult), a masonry professional will repoint brick siding for $5-$20 per square foot.

Efflorescence—the powdery white residue that sometimes appears on brick and stone surfaces—is the result of soluble salts in the masonry or grout being leached out by moisture, probably indicating the masonry and grout was never sealed correctly. Remove efflorescence by scrubbing it with water and white vinegar mixed in a 50/50 solution and a stiff bristle brush. As soon as the surface is clear and dry, seal it with a quality masonry sealer to prevent further leaching.

Persistent efflorescence may indicate a moisture problem behind the masonry. Consult a professional building or masonry contractor.

Remove mildew from all types of siding

Stubborn black spotty stains are probably mildew. Dab the area with a little diluted bleach—if the black disappears, it's mildew. 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. 

Repair cracked stucco

Seal cracks and small holes with color-matched exterior acrylic caulk. Try pressing sand into the surface of wet caulk to match the texture of the surrounding stucco. Paint the repair to match.

Take time to inspect and clean your house siding, and you'll be rewarded with a trouble-free exterior.