The north wall has gone green. The roof has black streaks down the side under the pines. Someone on the street says to rent a pressure washer for the weekend.
Please don’t point it at the house. Most of what grows on a home around here is algae and mildew, and both come off with chemistry, not force. That is what a soft wash is. We use it on roofs and on walls, and we keep the pressure washer for concrete.
What a soft wash is
A soft wash has three parts. A cleaning solution goes on at low pressure, about what a garden hose puts out. It sits for a few minutes and does the work. Then everything gets a gentle rinse from the top down. Nothing scrubs and nothing blasts.
What goes in the sprayer depends on the surface and how heavy the growth is. Ask Chris what he’s using on your house and he’ll tell you.
The shingle makers back this up. The Asphalt Roofing Manufacturers Association says in its bulletin on algae discoloration not to use a power washer, a brush or a broom on asphalt shingles. Friction and pressure loosen granules, and granules do not grow back. The same bulletin says the roof gets slippery during cleaning and points homeowners to a professional. We agree with both.
Soft wash or pressure wash, surface by surface
People often ask which surfaces can take pressure. Here is the short version.
| Surface | What we use | Why |
|---|---|---|
| Asphalt shingle roof | Soft wash only | Pressure strips granules. See our roof cleaning page for the streaks. |
| Painted siding and trim | Soft wash | Pressure lifts paint and forces water behind the boards. |
| Brick and mortar | Soft wash | Older mortar in Spring crumbles under a pressure tip. |
| Stucco | Soft wash | Pressure pits the finish and opens hairline cracks. |
| Soffits, fascia and gutter faces | Soft wash | Thin aluminum dents, and spray goes up into the attic vents. |
| Driveways, walks and patios | Pressure wash | Concrete can take it. That job lives on our driveway and concrete page. |
The walls of the house are covered in more detail on the house washing page. This page is about the method itself, and the method is the same whichever wall it is on.
Why the shady side goes first
Shade and damp. The pines keep the north wall and the north slope from drying out after rain. The algae that ARMA names, Gloeocapsa magma, travels on the air and settles wherever a surface stays wet. Its dark pigment is what streaks a light roof.
Expect it to come back. ARMA is honest about that too: cleaning lightens the stain and the stain can return. On a shaded wall it comes back sooner than on a sunny one. That’s the nature of algae, not a sign the wash failed.
In The Woodlands the Township’s residential standards list removing exterior algae and mildew from the dwelling as the owner’s job, so a green wall can also bring a letter. A soft wash is the fix that does not cost you paint.
What happens on the day
- We walk the house with you and note what is growing where. If the driveway is on the list, the cars come out first.
- Patio cushions, the grill cover and anything on the porch get moved. We wet down the flower beds near the walls.
- The solution goes on from the ground or from a ladder, one wall or one slope at a time, and sits while it works.
- Everything gets rinsed at low pressure, top to bottom, and the beds get rinsed again.
- You get before and after photos of every side we touched.
Keep pets inside while the solution is on the walls, and give the plants a drink afterward. Most houses take a morning.
Roof first, then the treatment
On a shingle roof the soft wash is step one of a rejuvenation, and it is the same wash whether you book the treatment or not. If the roof is on your list, the free roof inspection comes first, with photos of every slope, so you know what you are cleaning and whether it is worth treating.
Needles in the gutters come out on the same visit if you want them to. That is our gutter cleaning, and the two jobs share a ladder.
What it costs and what to do next
Chris prices a soft wash after he has seen the surfaces, by the size of the house and how heavy the growth is. You get the number before anyone starts, and it does not change on the day.
Call or text (281) 466-7436, or book the free assessment and tell us which walls have gone green. Everything else we do outside is on the pressure washing page.
Common questions
Will a soft wash damage my shingles?
No. The pressure is close to a garden hose and nothing touches the surface. The cleaning solution does the work and the rinse carries it off. What damages shingles is a pressure tip or a brush, which strip the granules that protect the asphalt. That is why the shingle makers' own guidance says not to power wash a roof, and why we never do.
How long does a soft wash last?
It depends on how much shade and damp the surface gets. A sunny wall stays clean longer. A north wall under pines greens up again sooner, because the algae lands wherever it stays wet. Treat a repeat on the shady side as normal rather than a failed wash.
Do I need to be home for a soft wash?
Not for the whole job, but the first ten minutes help. We walk the house with you, agree on what gets cleaned, and note what to move. After that, keep pets inside while the solution is on the walls and leave the cars out of the driveway if concrete is on the list. You get photos of every side when we are done.