If your siding looks worse after a pressure wash, the damage has a cause you can trace. This guide shows what pressure damage looks like on each material, how a jet does it, how to check for water behind the wall and what to do next, then explains why low-pressure soft washing is the safer method and where it has limits.
In This Article
The damage you might be seeing
- Vinyl: cracked, bowed or unlocked panels, gouged surfaces and dirty water trails from behind the laps.
- Painted wood and cedar: a fuzzy, raised grain where fibres were torn, stripes where the spray passed, stripped paint and splintered edges.
- Fibre cement: a dulled or washed-out paint film and open joints.
- Stucco: a pitted finish and cracks that are wider than they were.
- Brick: eroded mortar joints and sandy grit at the base of the wall.
- Asphalt shingles: bare patches where granules were blasted off, and lifted tabs.
- Everything else: torn screens, stripped caulk and water in light fixtures or outlets.
How a jet does this
A pressure washer squeezes a flow of water through a small opening, which concentrates its force into a narrow jet. Three things multiply the damage: a narrow spray angle, a short distance from the wall and an upward angle. A tight nozzle held close is closer to a cutting tool than a rinse.
The upward angle is the sneaky one. Siding is built to shed water that falls from above. A jet aimed up under a lap or a trim edge pushes water in the direction the wall is designed to keep it out, past the outer layer and into the cavity behind. From the ground you cannot see that happening.
A wide tip and a lower setting reduce the risk, but they do not remove it. Older vinyl turns brittle in the sun and cold, and wood, stucco and old mortar tolerate far less force than a driveway does. The same machine that is right for concrete is wrong for a wall.
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Check for water behind the wall
Damage on the surface is only half the picture. Over the following days and weeks, look for:
- Stains, bubbling paint or a musty smell on interior walls below the affected siding, particularly around windows.
- Damp or darkened trim and sills that stay dark long after the outside has dried.
- Streaks running down from the bottom edge of laps, or paint peeling on the exterior soon after the job.
- Soft spots in trim or sheathing when you press gently with a screwdriver tip.
Some signs appear within days, such as streaks and interior stains. Others take a season, such as peeling paint, a musty smell or soft trim. Check again after the next heavy rain and again after the first freeze-thaw stretch, because trapped water expands when it freezes.
If it already happened: a seven-step plan
- Document it. Take dated photos in daylight, wide and close, and write down the date and who did the work and how.
- Look inside. Check the interior walls, window frames and ceilings under the eaves, and repeat after a few days.
- Stop cleaning. Do not use the same method to fix what it broke.
- Tell the contractor in writing, with your photos. Ask how they handle problems and who their insurer is.
- Get an independent look. A siding contractor or building inspector can check for water inside the wall.
- Dry before you close. Damp walls should be dried out before panels are replaced or paint goes on.
- Repair the surface. Replace cracked panels, reseal joints and repaint where paint has been stripped.
If the work was your own, ask your insurance broker what your policy covers.
Why soft washing is safer, and where it has limits
Soft washing keeps force off the wall. The cleaning mix does the work, and low-pressure water only rinses. Nothing is aimed at a lap, joint or grain, so nothing is driven into the wall. See soft washing versus pressure washing for the wider comparison.
It is not risk-free. The risk moves from force to chemistry, so plants, metal and finishes need protecting, and a wash cannot repair damage that has already happened. Once a wall is clean, worn spots can show up more clearly. For upkeep after repairs, see how to maintain vinyl siding.
Next time, take dated photos of every wall before any work starts, since before-and-after pictures are the simplest way to separate new damage from old. D&D quotes soft washing free and in writing before work begins.
Key Takeaways
- Pressure damage shows up as cracked vinyl, furred wood grain, pitted stucco, eroded mortar, bare shingles and stripped caulk.
- A tight nozzle held close and angled upward drives water behind laps, into the cavity where you cannot see it.
- Check inside for stains, damp trim and soft spots over the following weeks, then document, tell the contractor in writing and get an independent inspection.
- Soft washing keeps force off the wall, but it moves the risk to chemistry and cannot repair damage already done.
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