Damage from too much pressure

What goes wrong, surface by surface

Concrete: stripes and etching

Concrete can take a lot, but a zero-degree or 15-degree tip held a few inches away cuts into the cream on top and leaves wavy lines that are permanent. Using a surface cleaner prevents most of it. So does keeping the wand moving.

Wood decks and fences: furring and gouges

Pine and cedar are soft. Too much pressure lifts the fibers into a fuzzy, splintery surface and carves grooves that catch dirt and show through stain. The fix is sanding, which costs more than the wash.

Siding: water where it shouldn't be

Spray aimed upward under vinyl laps pushes water into the wall. It can also tear siding off its nailing strip, chip paint off wood siding, and gouge stucco.

Windows and seals

High pressure on double-pane windows can break the seal, which shows up later as fog between the panes. Screens tear. Caulk gets blown out.

Roofs

Shingle granules wash off, and many manufacturers say pressure washing voids the warranty.

Quick rules if you're doing it yourself

1. Start with the widest tip, usually 40 degrees, and move in only as needed.
2. Keep at least a foot or two of distance on anything that isn't concrete.
3. Keep moving; never hold in one spot.
4. Spray down and across, never up under laps or flashing.
5. Use a surface cleaner on flatwork.
6. Leave roofs and second-story siding to someone with a soft wash setup and ladders.

Want it done for you? See driveway washing or house washing.

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