How Do I Care for My Home's Exterior Siding?

Siding is the home's raincoat, and like a raincoat it fails at the seams before it fails in the middle. Most siding problems show up where sections meet: at corners, around windows and doors, at the roofline, and where the bottom edge meets the foundation. Water that gets behind the siding travels down the wall, and by the time it shows indoors as a stain, the wall below has been wet for a long time. Care is simple: keep the siding clean, inspect the joints, and fix small damage before it becomes a wall repair.

Cheap maintenance beats expensive remediation in every siding type. Vinyl siding is low maintenance but cracks in cold weather if struck; aluminum dents and needs gentle handling; fiber cement performs well but needs proper painting at joints; and wood siding, common on older homes throughout the Main Line and Bucks, needs a repainting or staining cycle on a schedule or the boards rot from the ends and edges.

Clean the siding once a year, usually in late spring, when the worst of the pollen and winter grime are done. Start from the bottom and work up with a garden hose, sprayer, and a soft brush or long-handled scrubber, using a mild detergent if there is visible grime, mildew, or green growth near the foundation or on the north side, which stays damp longest. Rinse from the top down so dirty water runs off clean siding rather than streaking it.

Resist pressure washing on high settings. A consumer pressure washer on full blast can blast water behind siding, under window flashing, and up under the bottom edge, exactly where you do not want it, and it can shred soft wood, foam, and caulk joints. A gentle setting, held at an angle and at a distance, is fine if you use one at all, and many homes never need it. The scrub and rinse approach removes mildew without the risk.

Match the cleaning method to the siding material so the yearly wash does not become the yearly damage. Vinyl scrubs clean easily and tolerates moderate pressure, but it can crack in cold weather, so save heavy work for warm days. Aluminum cleans like vinyl but dents where hit, so keep ladders and tools away from the skin of the house. Fiber cement scrubs like masonry and holds its factory paint well when the edges are properly sealed. Wood needs the gentlest touch of all: wash with a soft brush in the direction of the grain, rinse promptly so water does not wick into the joints, and let it dry fully before any painting or caulking. Whatever the material, work in sections, top to bottom, so streaking runs over already dried areas rather than into clean ones. Siding cleaned the way its material prefers stays bright, dry, and problem-free for the whole year between washes.

Once a year, walk the perimeter and look at the seams first. Check that caulking around windows, doors, and corners is intact and flexible; reapply exterior caulk at any gap where water can enter. Look for cracked or missing pieces of vinyl, dented aluminum, chips in fiber cement, and any board of wood siding that is soft, cupped, or shows dark rot at the end grain. Pop a loose nail back in with a siding nail and carpenter's glue where needed.

Check trim, the painted boards at corners and rooflines, because rotted trim lets water behind the siding, and check the bottom row of siding against the foundation, keeping plants and mulch pulled back a few inches so moist soil does not sit against the siding all season, a slow trick that rots the bottom edges in older homes. Replace damaged pieces promptly: a cracked vinyl panel leaks once a storm drives water laterally, and a soft wood board spreads rot to its neighbors.

Our climate gives siding a full stress test every year.

• ✓ Spring: Clean the siding, check for winter impact damage, and scrape and spot-paint any nicks before summer sun bakes them.
• ✓ Summer: Trim branches and vines away from walls; vines and siding are a slow-motion disaster that traps moisture.
• ✓ Fall: Recaulk gaps and window joints before winter, and confirm downspouts move water away from the siding line.
• ✓ Winter: Clear snow piled against the siding, which melts and refreezes inside the wall when it sits high against the bottom row.

If you are selling, fresh siding was one of the first things buyers notice from the street; if you are buying, siding condition tells you a great deal about how the roof and windows above it have been treated.