Soft Washing vs. Power Washing: Which One Your Surface Needs

The difference between soft washing and power washing is pressure and chemistry. Power washing uses high-pressure water to physically strip dirt off hard surfaces like concrete, stone and brick. Soft washing uses low pressure plus a cleaning solution that kills mildew, algae and moss, and it is the right method for vinyl siding, painted wood, decks and asphalt shingle roofs. Use high pressure on the wrong surface and you can crack siding, gouge wood, or strip the granules off a roof.

Most houses need both: power washing for the driveway and walks, soft washing for the walls and roof. Here's how to tell which is which.

What is power washing?

Power washing (people use "pressure washing" for the same thing) sends a narrow, high-pressure stream of water at a surface. The force does the cleaning. It is very good at pulling ground-in dirt, tire marks, and growth out of the pores of concrete, and at clearing the joints between pavers and stones.

That same force is the problem on softer materials. A narrow stream held too close can etch concrete, blow sand out of paver joints, and cut into wood.

What is soft washing?

Soft washing uses about the pressure of a garden hose. The cleaning comes from a solution applied to the surface that kills the organic growth (mildew, algae, moss, lichen) and loosens dirt. After it has had time to work, the surface gets a gentle rinse.

Because it kills the growth at the root rather than knocking the top layer off, a soft wash usually stays clean longer. It also doesn't force water into places it shouldn't go. Our soft washing page walks through the process we use.

Soft washing vs. power washing by surface

Why high pressure damages vinyl siding

Vinyl siding is built to shed water running down it, like rain. It isn't built to stop water fired upward at the seams. A pressure washer aimed at an angle can push water behind the panels, where it sits against the sheathing. High pressure can also crack older, brittle panels, especially on a cold day, and knock panels loose.

If you have your siding manufacturer's care instructions, read them. Some manufacturers set pressure limits or advise against pressure washers entirely. Soft washing avoids the question.

Why high pressure damages wood

Wood is soft compared with concrete. A pressure washer tears the softer wood fibers away between the harder growth rings, which leaves the surface rough and fuzzy. Hold the wand still for a second and you get a visible line or gouge. On painted wood, high pressure lifts the paint along with the dirt.

Decks can be cleaned with low pressure and the right technique, but most of the cleaning should come from the solution, not the force.

Why you should never pressure wash a shingle roof

This one isn't our opinion. The Asphalt Roofing Manufacturers Association says high-pressure washing systems are likely to damage asphalt roofing and should not be used to remove algae, and it warns against scrubbing because friction can loosen and remove the granules (ARMA, "Algae Discoloration of Roofs").

Those granules protect the shingle from the sun. Strip them and the roof ages faster. The black streaks on a lot of Vermont roofs are algae, and a soft wash is how you treat them.

When power washing is the right call

Hard, durable, horizontal surfaces are what power washing is for:

• Concrete driveways with tire marks and winter grime
• Walkways and steps that have gone slick with growth in the shade
• Dumpster pads with grease and spilled food
• Patios before summer
• Gas station aprons and storefront sidewalks

Even then, technique matters. The tip, the distance, and the angle all change what the water does. See our power washing service page for what we handle, or our local guide to pressure washing in Rutland, VT.

Doing both on one property: the order matters

When a house needs a roof treatment, a siding wash and a driveway cleaning, the sequence makes a difference. Water runs downhill, and dirty water lands on whatever is underneath it.

1. Roof first, with a soft wash, so the runoff comes down before anything below is cleaned.
2. Siding next, working the solution on and rinsing from the top down.
3. Decks, porches and railings after the walls above them are done.
4. Walkways, patios and the driveway last, with power washing, so they aren't dirtied again by water coming off the house.

Plants get wet down before the cleaning solution goes on and rinsed again at the end.

Signs a surface got too much pressure

If a previous cleaning was done with too much force, you can usually see it:

• Light-colored lines or "zebra stripes" across a concrete driveway.
• Wood deck boards that feel fuzzy or splintered, with visible lines where the wand passed.
• Empty joints between pavers where the sand washed out.
• Bare spots or granules collecting in the gutters below an asphalt roof.
• Paint peeling in strips on siding or trim soon after a wash.
• Recessed, sandy mortar between bricks.

Some of this can be repaired, some can't. All of it is easier to avoid than fix.

How to tell what your house needs

Walk around the outside and sort what you see into two piles:

1. On the ground and made of concrete, stone or brick: power washing.
2. On the walls or roof, or made of vinyl or wood: soft washing.

Green or black streaks on the shady side of the house, dark stripes down the roof, and gray, slippery deck boards are all growth, and all soft wash jobs. Ground-in dirt and stains on the driveway are pressure jobs.

If you're in the Burlington area, our Burlington hiring guide covers what to ask any contractor before they start.

Get the right method for each surface

We do both, and we'll tell you which part of your property needs which. Request a free quote on the contact page or book through the booking page. You can also call (802) 558-3533, Monday through Saturday, 7am to 5pm.