The short answer
Every two to three years suits most Michigan homes, because a proper soft wash kills growth at the root rather than rinsing it off. Heavy shade, lakeside humidity and north-facing walls shorten the cycle toward annual. The real trigger is visual: green film, black streaks or a chalky hand-swipe means it is time regardless of the calendar.
The Short Answer, Then the Honest One
Two to three years between washes keeps most Southeast Michigan homes clean, protected and photogenic. That interval assumes the previous wash was done correctly — a soft wash that killed the algae and mildew rather than a pressure rinse that shaved the visible growth and left the roots. Pressure-only cleaning resets the clock to months, which is where the "I wash every year and it never lasts" frustration comes from.
What Shortens the Cycle
| Condition | Why it accelerates growth | Realistic cycle |
|---|---|---|
| Heavy tree cover / deep shade | Walls never fully dry; spores rain down constantly | 12–24 months |
| Lakeside and canal homes | Persistent humidity plus insect residue | 12–24 months |
| North-facing walls | Least sun, longest damp — first to green | Often yearly on that wall alone |
| Sprinklers hitting siding | Regular wetting plus mineral feed | Fix the head, then normal cycle |
| Full sun, open lot | Fast drying starves growth | 3+ years is common |
Around Harrison Township and St. Clair Shores, the lake effect is real: waterfront homes green faster than the same vinyl two miles inland, and the annual fish fly cleanup often becomes the natural wash cadence.
Read the House, Not the Calendar
- Green film on any wall — algae established and spreading
- Black streaks on the roof — Gloeocapsa magma, eating limestone filler, worth treating before lichen follows
- Chalky residue on your palm after touching siding — oxidation ready to shed onto the next rain
- Spider webs and insect buildup at eaves and corners — the food chain that follows organic film
- Gray, dull concrete that used to be light — embedded grime plus the start of surface wear
Any one of these says the interval is over, whatever the receipt says.
Frequency is not the risk — intensity is. A correct soft wash is non-destructive, so washing "too often" costs money without harming anything. One careless high-pressure wash does more damage than twenty years of proper ones. If you enjoy an annually spotless house, there is no penalty for it.
The Whole-Exterior Schedule
House siding: 2–3 years. Roof treatment: 3–5 years after a proper soft wash. Concrete: cleaned every 1–2 years, resealed every 5–10 with a penetrating product. Gutters: cleaned twice yearly regardless — that one is about water management, not appearance. Decks and fences: every 1–2 years depending on exposure. Bundling whichever items come due into a single visit is the cheapest way to run the whole rotation.
The Bottom Line
Two to three years for most homes, annual for the shaded and the lakeside, and immediately when the house tells you — because the growth you can see is farther along than it looks. A proper soft wash makes the interval real; a pressure rinse makes it a subscription.
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