Soft washing vs pressure washing: which one your siding actually needs
Green streaks on vinyl are algae, not dirt, and blasting them with high pressure drives water behind the siding. What we use on a house, what we use on concrete, and why the two are not the same job.
The photo above is a house in Wasaga Beach we cleaned this week. Same wall, an hour apart.
The green running down the panels was not dirt. It was algae, and that is the single most useful thing to know before anyone points a wand at your house, because dirt and algae come off in completely different ways.
The difference in one paragraph
Pressure washing uses force. High-pressure water blasts material off a hard surface. It is the right tool for concrete, pavers, and stone.
Soft washing uses chemistry. Low pressure, roughly what comes out of a garden hose, plus a cleaning solution that kills the algae and mildew at the root. The wall is then rinsed. It is the right tool for anything with a seam in it, which means siding, soffit, fascia and stucco.
The mistake is treating the second job as the first.
Why high pressure is wrong for siding
Vinyl siding is not a sealed surface. It is overlapping panels with gaps behind them by design, because the material expands and contracts through a Simcoe County winter and needs somewhere to go.
Point a 3,000 psi wand at that and water goes behind the panels. It gets into the sheathing, the housewrap and sometimes the insulation, and it does not come back out in a hurry. What you notice months later is a musty smell, a soft patch of drywall on an inside wall, or paint lifting under a window. None of it looks like it came from a pressure washer, which is why the connection usually gets missed.
The other problem is that pressure does not kill algae. It knocks the surface growth off, so the wall looks clean for a few weeks, and then it comes back darker because the roots were never touched. If your siding was washed last summer and looked bad again by autumn, that is what happened.
Where pressure washing is right
Concrete driveways, walkways, patios, retaining walls and stone. Solid, sealed, no seams for water to get behind. On those a proper surface cleaner takes off years of grey without leaving the wand marks you get from waving a straight jet around.
We do not do driveway washing as a standalone service. It comes up as an add-on when we are already at a house doing windows or siding, and that is worth knowing before you call us about a driveway on its own.
What the algae is actually telling you
Green and black streaking is not spread evenly around a house. It concentrates where the wall stays damp longest, which is almost always:
- The north elevation, which never gets enough sun to dry out
- Under a soffit or overhang where wind cannot reach
- Anywhere trees hang close enough to hold moisture against the wall
- The lower third of the wall, where splash-back off the ground keeps it wet
If your streaking follows that pattern, it is biological. If it is even across the whole house, it is more likely road grime or pollen, and it comes off easily.
What a soft wash costs around here
Most Simcoe County homes run $300 to $600 for the full exterior, depending on size and how much of it is reachable from the ground. A single elevation, which is often all that needs doing, is less. Bundled with a window clean on the same visit it comes down again, because most of the cost of any exterior job is getting a crew and a truck to your house.
How to tell if someone is doing it right
Ask what pressure they are running on your siding. If the answer is a number in the thousands, or if they cannot answer, that is your signal.
A proper soft wash looks slow and slightly boring. Solution goes on, it sits for a few minutes and does the work, then it gets rinsed off at low pressure. Nobody is leaning into a wand. The dramatic-looking version, where a jet strips a stripe of wall in one pass, is the version that pushes water behind your panels.
Also ask what happens to the beds underneath. The solution that kills algae will burn plants if it is left to sit on them. We wet down the beds first and rinse them after, which takes an extra ten minutes and is the difference between a clean wall and a dead hosta.
We soft wash siding, soffit and fascia across Simcoe County and Muskoka, and pressure wash hard surfaces on the same visit. Soft wash and pressure washing, or get a price in about thirty seconds.
Call or text (705) 718-1856.
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