If your siding has green or dark streaks — especially on the north side of your home — it’s almost certainly algae. It’s extremely common in Greater Cleveland and the rest of Northeast Ohio, and it’s not just an appearance problem.
## What Causes Green Algae on Siding?
Algae (and the dark staining you often see alongside it, which is usually mold or mildew) thrive in three conditions:
– **Moisture** — Lake Erie and Ohio’s humid climate provide this in abundance
– **Shade** — North-facing walls and tree-shaded surfaces stay damp longer
– **Organic material** — Dust, pollen, and dirt on siding provide nutrients
This combination exists in virtually every Northeast Ohio neighborhood, which is why algae on siding is so common here.
## Why DIY Solutions Rarely Last
**Garden hose and scrubbing:** Removes visible algae but leaves root structures in the surface — regrowth in weeks.
**Consumer pressure washers (1,500–2,000 PSI from the hardware store):** Often too aggressive for siding (risk of damage) but not effective enough with the cleaning agents needed. Also miss areas behind trim and in hard-to-reach spots.
**Bleach mixtures from the internet:** Can work temporarily but straight bleach applied improperly damages landscaping, strips paint, and can void vinyl siding warranties. Without a surfactant to make it cling to vertical surfaces, it runs off before it has time to work.
## How Professional Soft Washing Removes Algae Long-Term
Professional soft washing uses:
1. **Sodium hypochlorite (properly diluted)** — kills algae, mold, and mildew at the cellular level
2. **Surfactants** — allow the cleaning solution to cling to vertical surfaces and penetrate the algae layer
3. **Low pressure** — safe for all siding types, won’t force water behind panels
4. **Thorough rinsing** — removes dead organic material and cleaning solution completely
The result: algae killed at the root, results that typically last 12–18 months rather than a few weeks.
## What About Algae on Brick?
Brick is porous and algae penetrates deeper than it does on vinyl. Professional cleaning still works well — it just may require a stronger solution and a second pass on heavily affected brick. The north side of brick homes in older Cleveland neighborhoods (Rocky River, Lakewood, Fairview Park) often has years of accumulated algae that needs a thorough professional treatment.
## Mr. PowerWash House Washing Service
We use professional soft wash systems across Greater Cleveland. Free estimates, same-week scheduling in most cases.
**[Get a Free Estimate](https://mrpowerwash.co/contact/)** | [(440) 477-6275](tel:+14404776275)
Serving Parma, Avon, Avon Lake, Berea, Brunswick, Strongsville, Medina, North Olmsted, Lakewood, Rocky River, Westlake, Bay Village, Fairview Park, and all of Greater Cleveland.