The short answer
Century homes are washed by protocol, not pressure: test the mortar (pre-1930 lime mortar dissolves under blasting), assume lead-era paint and work wet at low pressure, protect original glass and glazing putty, and let chemistry with long dwell times do what force must not. Done right, no home rewards washing more.
A Century House Is an Archive. Wash It Like One.
The county seat has the county's oldest housing stock, and the streets around downtown Mount Clemens hold homes from the 1890s through the 1920s that have outlasted every trend since. Washing them is genuinely different work — not harder, but governed by rules that don't apply to a 1995 colonial. Break the rules and you don't just mark the house; you erase original material nobody can reorder.
Rule One: The Mortar Is Softer Than You Think
Masonry laid before roughly 1930 used lime mortar — a softer, breathing binder that Portland-cement thinking destroys. Pressure that modern brick shrugs off carves lime joints visibly in seconds, and repointing a century wall costs more than a decade of washing. Old masonry gets tested first, then cleaned with chemistry and rinse pressure only. (The full masonry logic is in our brick guide — the pre-1930 section is the one that matters here.)
Rule Two: Respect the Paint History
A century of coats sits on that clapboard, and layers below 1978 should be presumed lead-bearing. That's not a reason to avoid washing — it's a reason to wash correctly: low pressure that cleans the surface without chipping or pulverizing old layers, everything kept wet, no dry blasting ever. (Any sanding or scraping project belongs under EPA lead-safe practices — washing done right stays upstream of all that.) The same gentleness protects the wood itself: old-growth siding is irreplaceable-grade lumber wearing many thin coats, and it cleans beautifully under patient chemistry.
Rule Three: The Glass and Putty Are Originals Too
Wavy cylinder glass and hand-tooled glazing putty survive on many of these homes. Direct pressure streams crack century glass and blow out dried putty lines wholesale. Windows get perimeter respect — solution applied gently, rinsed from above at an angle, never jetted at the glazing. The reward for care: original glass, professionally detailed, has a depth no replacement unit matches.
The dividend on doing it right: no housing stock transforms like this one. A century of architecture emerging from decades of gray film — porch turnings, cornice brackets, brick patterning sharp again — is the most dramatic before-and-after in the trade.
The Bottom Line
Pre-1930 homes wash on protocol: mortar tested, pressure near zero, chemistry patient, originals protected. It's the difference between cleaning an archive and sandblasting one — and it's exactly the work our soft-wash process was built for.
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