Green Algae on Siding: Why It Grows and How to Remove It

Green algae on siding grows because lake humidity, tree shade and shaded north-facing walls keep siding damp for long stretches. The safe way to remove it is a low pressure soft wash with a cleaning solution that kills the growth, since pressure washing can force water behind the panels.

Why do west side homes get green algae on siding every year?

Homes in Rocky River, Bay Village, Westlake and the rest of Cleveland's west side deal with green algae and black mildew almost every season. A few local conditions work together to keep siding damp, and damp siding is where growth takes hold.

The growth usually shows up first on the shady side of the house, then spreads. Once it starts, it tends to come back every year unless it is properly killed.

• Lake Erie keeps humidity high through the warmer months
• Heavy tree cover shades siding so it cannot dry out between rains
• North and east-facing walls get the least sun and stay wet longest
• Spring rain, summer humidity and freeze-thaw cycles keep moisture around most of the year

Is algae on siding just a cosmetic problem?

No. Green algae and black mildew make a house look neglected, but left alone for several seasons, organic growth can also wear on the siding itself.

Long-term growth can void siding warranties and lead to costly replacement. Cleaning it off regularly is far easier than replacing panels.

Cleaning also makes it easier to spot real problems early. Once the green film is gone, loose panels, damaged trim or peeling paint are much easier to see and fix.

Can you pressure wash algae off siding?

You should not. Pressure washing siding is one of the most damaging mistakes a homeowner can make.

High pressure water can force moisture behind the siding and cause mold growth inside the walls. It can also etch and permanently mark vinyl and strip paint from wood.

Pressure also only knocks the growth off the surface. Whatever survives can grow back, so a pressure washed wall can turn green again in a short time while you are left with the damage.

How does soft washing remove green algae on siding?

Soft washing applies a cleaning solution at low pressure that kills algae and mildew at the root, then rinses it away. Since the growth is killed instead of just knocked loose, the siding stays clean longer.

Before we start, we soak the landscaping, and we rinse it again when we finish. It is the same process we use on vinyl, aluminum, wood and stucco.

If your roof or gutters show the same green or black streaks, they can be soft washed on the same visit. Bundling services on one visit saves money, and window cleaning with purified water is a common add-on once the siding is clean.

Getting algae off your siding with Purified Wash

Purified Wash removes green algae, black mildew and organic staining from siding in Rocky River, Bay Village, Westlake, Avon Lake, North Olmsted, Fairview Park, Lakewood and nearby towns. The company carries $1 million in general liability coverage, and we can send a certificate on request.

What to look for in a company: ask how they clean siding, whether they protect the landscaping, and whether they carry insurance. A clear answer to all three tells you a lot.

There is no deposit, and you pay after the job is done. Book a free in-person quote online or text (440) 865-8993, and we will give you an exact price, often with time to do the work on the same visit.

Next steps

• House Washing (Soft Wash)