The black streaks running down asphalt shingle roofs all over southern Indiana aren't dirt — they're Gloeocapsa magma, an algae that feeds on the limestone filler in shingles. Left alone, it spreads across the roof, holds moisture against the shingle surface, and shortens the roof's life while making the whole house look tired from the street. Moss and lichen, common on shaded roof planes around here, are worse: they physically pry shingle granules loose.
The fix is not a pressure washer. Pressure washing an asphalt roof strips granules — the protective layer your shingles depend on — and voids most manufacturer warranties. The correct method, and the only one we use on roofs, is soft washing: a low-pressure application of the same style of cleaning solution roofing manufacturers recommend, allowed to dwell and kill the growth, followed by a gentle rinse or natural rain-rinse. The algae dies, the streaks release, and the shingles keep every granule they had.
What Roof Soft Washing Includes
- Full roof treatment — every plane, ridge to gutter line
- Moss and lichen treatment — killed in place; heavy growth releases over following weeks rather than being torn off (tearing removes granules)
- Gutter flush — runoff and debris rinsed through so it doesn't sit in your gutters
- Landscaping protection — everything below the roofline pre-soaked and rinsed
Is It Worth It vs. Replacing Shingles?
A soft wash costs a small fraction of a re-roof. If your shingles are structurally sound and just streaked, cleaning restores the appearance and removes the growth that's degrading them — that's years of additional service life for a few hundred dollars. If we get on site and see shingles that are actually failing, we'll tell you washing isn't the right spend. We'd rather lose a job than wash a roof that needs a roofer.
Pricing
Most single-story ranch roofs run $350–$600 to soft wash; larger and steeper roofs are quoted individually based on size, pitch, and growth. It pairs naturally with a house wash and gutter brightening for a full top-to-bottom refresh. Ranges and the reasoning behind them are in the cost guide.
Want ballpark numbers before you call? Read our pressure washing cost guide, the window cleaning cost guide, or learn why method matters in soft wash vs. pressure wash. Or skip the reading — back on the homepage you can see everything we do, and (812) 329-4733 gets you a straight answer fastest.