Pressure Wash Vinyl Siding: Reduce Water Intrusion Risks

To pressure wash vinyl siding without forcing water behind it, only go ahead if the instructions for your siding and your pressure washer both allow it. Hold the spray level and never aim it upward. Keep the stream out of panel laps, seams and openings.

These steps lower the risk, but they can't promise that no water gets behind the siding. If you see water getting behind the panels, or the siding is loose or damaged, stop. Switch to a gentler method that your siding maker allows.

How to Keep Water From Getting Behind Vinyl Siding

Safe vinyl siding pressure washing depends on two things: getting permission from the right instructions, then controlling the spray. Vinyl siding panels overlap. A spray aimed up under those overlaps can push water into the gaps.

A homeowner positions a Fanttik NB8 Nano spray gun level toward a vinyl siding panel before washing.

Find out who made your siding and which washer you have. The Polymeric Exterior Products Association (PEPA) says to read both manufacturers' instructions before you start. Some siding makers don't recommend pressure washing at all. Others set limits on pressure (PSI) and on which cleaners you can use.
Go ahead only if both sets of instructions allow it. Use the pressure, nozzle and cleaner limits they give. Don't borrow settings from a different washer or siding brand.
Keep the spray level. PEPA recommends holding the washer straight at eye level. Its guidance on level, non-upward spray says that aiming the stream upward can force water behind the siding panels.
Keep the stream out of laps and openings. PEPA advises care around windows, doors, electrical wiring and plumbing. Don't point the stream straight into panel laps or gaps, either. That's a practical precaution, not a rule with a set distance.
Use cleaner-specific directions only with that cleaner. Simple Green's vinyl siding instructions call for low pressure, a 25 to 40 degree nozzle tip, a downward angle, and at least 18 inches from the surface. Those settings belong to its own cleaner procedure. They don't replace your siding or washer instructions.

Flowchart showing the instruction check, safe spray direction, and conditions for stopping when pressure washing vinyl siding.

If you plan to add soap, first check that your washer and the cleaner label agree. Our guide to choosing electric pressure washer detergent covers how to match the two.

What the Siding and Washer Instructions Change

CertainTeed is one clear example of how much manufacturer rules differ. CertainTeed's siding instructions say it does not recommend power washing its vinyl or polymer siding, because doing so can cause moisture intrusion, damage or discoloration. That rule covers CertainTeed siding only. It doesn't apply to every brand, but it shows why general advice can't give you permission for your own house.

Your washer manual matters for a different reason. It tells you what your machine can safely do, such as its nozzles and pressure settings. A high PSI rating is a maximum, not the right setting for siding. For the difference between pressure and flow, our guide to balancing PSI and GPM explains how each one affects a surface.

When to Stop and What to Use Instead

Stop if:

Water runs out from under laps, or shows up around windows, doors or other openings
Panels are loose, cracked or pulled away from the wall
Your siding maker doesn't recommend pressure washing

Use this method instead, if your siding maker allows it. PEPA's hose-and-brush cleaning steps say a garden hose rinse is often enough for routine dirt. For a deeper clean, use mild soap with a soft cloth or a long-handled, soft-bristle brush. Work from the bottom of the wall up to prevent streaks. Rinse the solution off completely before it dries. CertainTeed recommends the same kind of hand cleaning and hose rinse for its own siding.

FAQs

Should I start at the top or the bottom of the wall?

When washing with soap, PEPA's steps say to start at the bottom and work up, which helps prevent streaks. Simple Green's procedure also applies its cleaner from bottom to top, then rinses with clean water from top to bottom.

How do I protect brick, stone, and plants nearby?

PEPA suggests covering brick or stone accents so cleaning runoff doesn't reach them. CertainTeed says a small amount of soapy water shouldn't harm plants. If you're worried, pick a soap without added perfumes, dyes or moisturizers, and test it on one plant first.

What if regular soap won't remove a stain like algae?

CertainTeed suggests asking your siding contractor for a cleaner made for your siding. Test any new cleaner on a small spot that's hard to see before you use it on the whole wall.