A Simple Power Washing Routine That Protects Your Paint

Washing is maintenance, not just cleanup. Dirt, pollen, and mildew hold moisture against a surface, and growth that sits long enough works its way into the finish instead of resting on top of it. A good routine handles three groups differently: siding and painted surfaces get a soft wash with a cleaning solution, concrete takes real pressure plus the right cleaner for oil and rust, and wood gets the gentlest treatment of all. Pressure is a dial that gets matched to the surface. Used wrong, the same machine that cleans a driveway will ruin a deck in one pass.

Wash Before Growth Digs In, Not After It Stains

Green and black streaking is living growth, and the longer it stays, the deeper it roots into the surface. Shaded walls, north sides, anything under a tree, and surfaces near sprinkler spray go first, so those are the places to check. Catching it early means a cleaning solution and a gentle rinse. Waiting means heavier work and sometimes a mark that never fully leaves. Walking the perimeter of the house a couple of times a year and looking at the shaded walls is the whole inspection.

Match the Pressure to the Surface, Every Time

Siding is built from overlapping pieces, and a hard stream aimed upward pushes water under the laps and into the wall. Soft washing does the job instead: a cleaner that kills the growth, time to work, then a gentle rinse from the top down. Concrete can take far more force, though a tight nozzle held close will still etch it and leave permanent wand stripes. Stucco, old mortar joints, and soft brick sit in the middle and give up quickly under a narrow tip. See power washing for how each surface is approached.

Decks and Fences Get Cleaned, Then Sealed

Cleaning wood without refinishing it is half a job, because a clean, unprotected board starts drinking water the next time it rains. Wood also needs the lowest pressure of anything on the property: a wide fan, real distance, steady movement, and passes that follow the grain. Damaged fibers drink stain unevenly later and show as dark streaks in the finish. Once the wood is clean and fully dry, it is ready for wood staining and sealing, and that order matters more than the products do.

Concrete Stains Need Chemistry, Not Force

Oil soaks into concrete, so the stain lives below the surface where water never reaches. Attacking it with a turbo nozzle usually leaves a clean ring around a stain that is still there, plus an etched circle you cannot undo. A degreaser that sits and pulls the oil up does the actual work. Rust has its own cleaners, and fertilizer rust, irrigation staining, and battery acid each respond to different products. Rinse the whole slab evenly afterward, or the clean spots become their own kind of stain.

Wash Before Paint, Then Let It Dry

Washing for looks removes dirt. Washing before a repaint has to remove chalk, mildew, webbing, and loose material, because primer and paint bond to whatever is left behind. Rub a dry hand on a sunny wall, and if it comes back dusty, that chalk has to go before any coating. Then the surface has to dry all the way through, not just on the face. Wood and stucco hold water much longer than they look like they do. Our post on what drives the price of an exterior paint job explains why this step shows up as its own line.

Keep the Wand Off This List

Never put a pressure wand on asphalt shingles, because it strips the granules that protect the roof and voids many shingle warranties. Roof streaking is handled with low pressure methods made for roofs. Also keep pressure away from window seals, screens, dryer vents, air conditioner fins, light fixtures, and soft mortar. Cover plants, rinse them well after cleaning solutions, and close up windows and doors before starting. RCAG Professional House Painting Brother offers power washing across the cities we serve near Austin.

Written by the RCAG Professional House Painting Brother team. Updated 2026-09-23.