There is no universal chart of correct pressures. What exists is a set of pressures and nozzle angles that manufacturers commonly specify for a given material, plus a much shorter list of things that are widely warned against. Both are worth knowing, and neither is a guarantee. Every surface has a history: a deck that has been sealed twice behaves differently from bare cedar, and thirty year old siding is not the same material as siding installed last year. The manual supplied with the machine governs, and where it names a setting for a material, that instruction takes precedence over any general guidance.
Vinyl and painted siding
Siding is the surface where the damage is least visible and most expensive. The hazard is not the panel. It is water driven behind the panel, into the sheathing and the wall cavity, where it does not dry.
Manufacturers commonly specify wide angle tips for siding, in the 25 to 40 degree range, and a working distance measured in feet rather than inches. The direction of the spray matters as much as the pressure. Lap siding overlaps downward, so a jet aimed upward drives water under the laps. Spraying across and slightly downward keeps water on the outside of the wall.
Machines in the lower part of the corded range suit this work. The RYOBI RY141820VNM, listed at 1,800 PSI and 1.2 GPM, and the Westinghouse WPX2300e are typical of that band. Note that the WPX2300e listing is internally inconsistent: the title states 2,300 max PSI and 1.76 max GPM, while the description on the same listing states max 3,000 PSI. Both figures come from the manufacturer, and the higher one is a reason to start further back rather than closer.
Painted wood siding adds a second problem. If the paint predates 1978 it may be lead based, and disturbing it with a pressure washer disperses the debris across the yard. That is a case for professional assessment rather than a nozzle choice.
Wood decks
Wood is soft, and softwood decking is very soft. Too much pressure raises the grain, leaves visible fan marks in the boards, and gouges anywhere the tip lingered. The damage often does not show while the deck is wet and appears clearly once it dries.
Manufacturers commonly specify the wide angle tips for wood and a moving wand that never stops in one place. Working with the grain rather than across it reduces visible striping. The turbo nozzles included with machines such as the CRAFTSMAN CMEPW2100 are not the tip for a deck surface, even though they are the fastest way to clear a stubborn deposit on concrete.
Composite decking is a separate case. Composite boards have a manufactured surface layer, and many composite manufacturers publish a maximum pressure in their own care documentation that is lower than what a mid range washer produces. That document, not the pressure washer manual, is the one that governs a composite deck.
Concrete, driveways and masonry
Concrete tolerates far more than wood, which is why it is where the higher output machines earn their keep. Flow matters more than pressure here because the job is large and flat, and gallons per minute is what moves the loosened material off the slab. The gas powered listings publish flow figures between roughly 2.4 and 4.0 GPM against 1.1 to 2.3 GPM across the corded electric listings, and that gap is the reason a gas machine finishes a driveway faster.
A surface cleaner attachment is the difference between an even result and a striped one, because it holds two spinning nozzles at a fixed height and spreads the work across a wide path. The Karcher 15 inch surface cleaner is listed as compatible with machines rated 2,600 to 3,200 PSI up to 2.7 GPM, and the LidoDola 14 inch surface cleaner suggests a machine of 2,500 PSI or above. Those figures describe what the accessory needs and can withstand, not what it produces.
Brick and mortar are less forgiving than they look. Old lime mortar erodes under a narrow tip, and the damage is structural rather than cosmetic. Wide tips and distance apply here even though the substrate is masonry.
Cars and vehicles
Automotive paint is a thin clear coat over a base coat. A narrow tip held close will cut it, lift edges of existing chips, and force water past door and window seals. Decals, pinstriping and plastic trim come off before the paint does.
Manufacturers commonly specify the widest available tip for vehicles, generous distance, and a machine at the low end of the range. The battery powered units in this catalog exist largely for this work: the DEWALT DCPW550B at a listed 550 PSI and 1.0 GPM, the WORX WG644 Hydroshot at 450 PSI and 0.90 GPM, and the RYOBI RY120350 at 320 PSI and 0.8 GPM all sit far below the corded machines by design.
Wheel arches and undercarriages are the exception, and this catalog carries dedicated attachments for them, including the Ridge Washer 24 inch undercarriage cleaner, whose listing states a working pressure range of 1,500 to 4,000 PSI. Attachments of that kind put the jet under the vehicle and keep the operator clear of the spray.
Patios, furniture and fences
Patio slabs behave like driveway concrete, and a smaller surface cleaner keeps the finish even in a confined space. The Westinghouse PWSC12 12 inch attachment is listed as rated up to 2,500 PSI on a quarter inch quick connect fitting, which is a size that fits between furniture legs and along edges where a 15 inch unit will not reach.
Plastic and resin furniture, painted metal, and fence pickets all sit closer to the deck end of the scale than the concrete end. Wide tips, distance and a moving wand apply, and fasteners in older fencing are worth checking before rather than after, because a jet will find a loose board.
Surfaces to leave alone
Roof shingles are the clearest example. Pressure lifts granules off asphalt shingles and drives water up under the courses. Roof cleaning is a low pressure chemical process, not a pressure washing job, and it is also work performed at height where jet recoil makes a ladder genuinely dangerous.
Windows, screens, electrical meters, exterior outlets, air conditioning coils, soffit vents and anything with a seal around it are all on the same list. So is old exterior paint that is already failing, because the washer will remove far more of it than intended.
Safety that applies on every surface
No surface justifies aiming the jet at a person or an animal. A pressure washer stream can drive water, grit and bacteria through skin and produce an injection injury, which can look like a minor puncture while causing severe damage in the tissue underneath. Any suspected injection injury is a medical emergency and needs assessment immediately rather than first aid. Eye protection and closed footwear are standard manufacturer instructions, because the jet throws back whatever it removes. Where a gas engine drives the pump, that engine emits carbon monoxide and must never be run indoors or in a garage, including with the door open.
