The difference in one paragraph
Pressure washing uses high-powered water to blast grime off hard, durable materials like concrete and stone. Soft washing uses low-pressure water - about the strength of a garden hose - combined with specialized, eco-friendly cleaning solutions that neutralize algae, mold, and mildew at the root. One removes dirt with force; the other removes growth with chemistry.
Which surfaces get which method
Pressure washing is for driveways, concrete pool decks, stone walkways, and other hard surfaces that shrug off force. Soft washing is for everything that cannot: vinyl, brick, and stucco (EIFS) siding, asphalt shingle roofs, painted surfaces, soffits and fascia, and wood decks and fences.
The reason is what high pressure does to those surfaces. It can crack vinyl panels, etch the face of brick and mortar, and force water into wall cavities where it causes hidden moisture problems. On a roof, high pressure strips the protective granules off the shingles and can void the manufacturer warranty - which is why the Asphalt Roofing Manufacturers Association endorses low-pressure cleaning only.
Why soft washing results last longer on siding
That green or streaked look on siding is a living colony of algae, mold, and mildew - not just dirt. Blasting it with water knocks off the visible layer but leaves the roots, so the growth returns quickly. Soft-wash solutions neutralize the organism itself, which is why a soft-washed home stays clean noticeably longer than one that was power washed.
What a professional actually does
A good exterior cleaner does not choose one method for the whole property - they match the method to each material. At PowerShine, a typical London home might get full pressure on the concrete driveway, a wood-safe low-PSI wash on the deck, and a soft wash on the siding and roofline, all in one visit, with plants pre-soaked and protected before any solution is applied.
