The short answer
Concrete and brick pavers take 3,000–4,000 PSI. Wood decks need 500–1,200 with a wide fan tip. Vinyl siding, stucco and screens should stay under 500 PSI, and asphalt shingle roofs should never be pressure washed at any setting. Professionals size the water volume (GPM) as carefully as the pressure — flow does the rinsing, pressure does the breaking.
The Number Everyone Asks About Is Half the Story
PSI — pounds per square inch — measures how hard the water hits. GPM — gallons per minute — measures how much water is doing the hitting. Homeowners shop by PSI because that is the number printed largest on the box; professionals buy by GPM, because once you have enough pressure to break a bond, it is flow that carries the dirt away.
A 3,000 PSI machine at 1.8 GPM (typical consumer unit) cleans a driveway noticeably slower — and stripier — than a 2,500 PSI machine at 5.5 GPM. Keep that in mind as you read the chart: the PSI column is a ceiling for safety, not a target for quality.
PSI by Surface
| Surface | Safe working pressure | Notes |
|---|---|---|
| Concrete driveway / sidewalk | 3,000–4,000 PSI | Use a surface cleaner, not a wand, or you will stripe it |
| Brick pavers | 1,500–2,500 PSI | Angle away from joints; re-sand after cleaning |
| Mortared brick walls | 500–1,500 PSI | Old lime mortar erodes fast — test low, stay low |
| Wood deck / fence | 500–1,200 PSI | Wide fan tip, with the grain; higher pressure furs the wood |
| Composite decking | Under ~1,500 PSI per most manufacturers | Check your brand — pressure damage voids most warranties |
| Vinyl siding | Under 500 PSI | Soft wash only; the cleaning solution does the work |
| Stucco / Dryvit | Under 500 PSI | Pressure cracks the finish coat |
| Windows / screens | Rinse pressure only | Direct pressure can break double-pane seals |
| Asphalt shingle roof | Never | Any pressure strips granules; soft wash is the only safe method |
| Vehicles | 1,200–1,900 PSI | 25–40° tip, never a zero-degree point |
The tip matters as much as the dial. A zero-degree red tip at 1,500 PSI concentrates more force on one spot than a 40° white tip at 3,000. Most consumer damage we see was done with the wrong tip, not the wrong machine.
Why Distance Changes Everything
Pressure at the surface falls off fast with distance. A wand held 6 inches from siding delivers several times the force of the same wand at 24 inches. This is why "I used a low setting" still cracks vinyl — the setting was low, the wand was close. Professionals control effective pressure with tip choice and standoff distance, not by trusting the dial.
Where the Chart Stops Mattering
Organic growth — the green film on siding, the black streaks on a roof — is alive, and pressure does not kill it. You can blast algae off a wall at any PSI and it regrows within months because the root structure survives. Those surfaces need soft washing: a cleaning solution at garden-hose pressure that kills the organism, covered in detail in our soft washing vs. power washing guide.
So the honest version of the chart is: hard mineral surfaces get pressure, everything that grows gets chemistry, and the roof gets chemistry only.
What We Actually Run
Our trucks carry commercial units in the 5.5–8 GPM range with heat, and we spend most of the day nowhere near their maximum pressure. A typical driveway cleaning runs a surface cleaner around 3,000 PSI; a house wash runs under 300 PSI at the surface. The machine's job is capacity, not violence.
The Bottom Line
Match pressure to the surface, choose the tip before you touch the dial, and remember that anything alive needs chemistry rather than force. If a surface is not in the chart above, start at the lowest setting from several feet away — you can always add pressure, but you cannot un-etch concrete or un-fur a deck board.
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