Home / How to Clean Painted Exterior Surfaces on a Pasadena Home

Cleaning Painted Walls and Trim Without Damaging the Finish

Paint lasts longer when it is kept clean. Dirt, pollen, bird droppings, cobwebs and the fine dust that blows through Pasadena during dry months all build up on exterior walls. Some of it is merely unsightly. Some of it holds moisture against the surface, feeds mildew, or slowly breaks down the finish. Regular, gentle cleaning keeps the paint looking fresh, extends the time between repaints, and lets you spot problems early, since a clean wall shows cracks, peeling and stains far more clearly than a dirty one.

How often to clean

Most homes benefit from a full exterior wash once a year, with spot cleaning in between as needed. In Pasadena, a good time for the annual wash is late spring, after the rainy season has ended and before summer heat sets in, when surfaces dry at a reasonable pace. A second, lighter rinse in the fall, before the rains, clears away summer dust and any residue left by wind events. Areas that attract more dirt, such as walls near driveways, the undersides of eaves where spiders gather, and walls under trees, may need attention more often.

Cleaning belongs to the regular upkeep described on pasadena house painting journal, and done gently it can put off a repaint by a season or more.

What you will need

A garden hose with an adjustable spray nozzle.
A soft-bristle brush on an extension pole, for walls and trim out of reach.
A bucket and a mild detergent, such as a gentle dish soap or a cleaner labeled safe for painted surfaces.
Soft sponges or cloths for trim, doors and details.
Safety glasses and gloves.
Plastic sheeting or tarps to protect sensitive plants if you are using any cleaning solution beyond plain water.

A basic washing routine

Walk the house first. Close windows, cover electrical outlets and fixtures, move furniture and potted plants away from walls, and note any loose paint or open joints. Aggressive washing of an area with failing paint can strip it further, so take care there.
Pre-wet plants and the wall. Soaking nearby plants with plain water first helps protect them from any detergent runoff. Wetting the wall loosens surface dirt.
Wash from the bottom up. When applying soapy water, work from the base of the wall upward. This prevents dirty solution from running down over dry, dirty areas and leaving streaks that are hard to remove.
Scrub gently. Use the soft brush with light pressure. The goal is to lift dirt, not scour the paint. On textured stucco, work the brush in small circles to reach into the texture.
Rinse from the top down. Once a section is scrubbed, rinse it thoroughly from the top, letting clean water carry the soap and dirt downward. Do not let detergent dry on the wall.
Work in manageable sections. Wash and rinse one area at a time so the cleaner does not dry before you rinse it off, especially on warm days.

Pick a mild, overcast morning or a shaded side of the house. In direct sun, water and detergent dry too fast and leave spots.

Dealing with mildew

Mildew grows in shade and moisture, so on Pasadena homes it is most common on north-facing walls, under dense trees such as oaks, behind shrubs planted close to the house, and in spots that stay damp from irrigation. It shows as gray, green or black speckling. A quick test is to dab a small spot with diluted household bleach. If it lightens within a minute or two, it is mildew. If not, it is probably dirt.

To clean mildew, use a solution made for the purpose, or a diluted bleach solution mixed according to label directions, applied with a soft brush and allowed to sit briefly before a thorough rinse. Never mix bleach with ammonia or with cleaners that contain ammonia, since the combination releases toxic fumes. Protect plants by wetting them before and rinsing them after, and cover delicate ones. Wear eye protection and gloves.

Cleaning removes the growth, but mildew will return unless the conditions change. Trim back shrubs so air can circulate against the wall, thin tree canopies where practical, and adjust sprinklers that wet the siding. When the wall is eventually repainted, a paint formulated with mildewcide may help in chronically shaded spots.

Common stains and how to treat them

Bird droppings. Remove them promptly, since they can be acidic and may etch or discolor paint if left for a long time. Soften with water, then wipe gently.
Cobwebs and insect residue. A soft broom or brush clears webs under eaves. Wash away the residue left behind with mild soapy water.
Tree sap. Fresh sap can often be lifted with warm soapy water. Test any stronger cleaner on a hidden spot first, since solvents can soften latex paint.
Rust streaks. Rust below fasteners or metal fixtures can sometimes be lightened with a cleaner made for rust stains, tested first. The long-term fix is dealing with the corroding metal.
Chalk runoff. White streaks running from a chalking wall onto a lower surface wash off with detergent and a soft brush. The wall itself will keep chalking, which is a sign it is aging toward a repaint.

What to avoid

Harsh abrasives, scouring pads and wire brushes will scratch and dull paint. Strong solvents can soften or remove latex finishes. Very hot water is unnecessary and can stress some coatings. High-pressure spray can drive water behind siding and into joints, gouge soft wood, and strip paint, so it needs far more care than a garden hose. Keep cleaning gentle, and escalate only as far as the stain requires.

After cleaning

Let everything dry completely, then walk the house once more. A clean wall reveals the true condition of the paint. Look for fading, hairline cracks, peeling edges and failed caulk that dirt was hiding. Make a note of anything that needs repair. If you are planning to repaint soon, a thorough cleaning is the essential first step anyway, since new paint needs a clean, dry, sound surface to bond to.

Give washed wood at least a couple of dry days before any touch-up, longer in cool or shaded spots, because wood holds rinse water well after the surface looks dry. Stucco also absorbs water and needs time to release it. Write down the date of the wash and anything you found, so next year's cleaning starts with a list of spots to watch rather than a fresh search.