local_context // san_jose_roofs
WHY SAN JOSE
ROOFS GROW MOSS.
San Jose is a tile town. Drive through Almaden Valley, Blossom Valley, Berryessa, or Evergreen and most of what you see is concrete tile — curved S-tile on the Mediterranean-style tracts, flat tile on the ranch homes, with asphalt shingle mixed into older neighborhoods like Willow Glen and Cambrian Park. Concrete tile is porous. It soaks up winter rain and marine-layer moisture, then holds it long after the street has dried. That trapped moisture is what Gloeocapsa magma — the black streaking algae — plus moss and lichen live on.
By year five or six without treatment, north- and east-facing planes start showing dark streaks. By year ten, moss is rooted in the tile overlaps and lichen is anchored to the face of the tile. At that point rain does not rinse it off — the growth is physically attached and feeding on the surface. Left alone, moss holds moisture against the tile through summer, lichen etches the finish, and the roof starts failing home-insurance inspections. That insurance letter is the single most common reason San Jose homeowners call us.
> Soft wash under 500 PSI — the only method we use
A pressure washer running at driveway pressure will blast growth off a tile roof — along with the tile's cured surface layer, and often pieces of the tile itself. Cracked tiles, blown-out ridge mortar, stripped color coat. On shingle, high pressure strips the granules that protect the asphalt from UV and voids the manufacturer warranty. Our process is chemical, not mechanical: a biodegradable algaecide applied at under 500 PSI, given time to penetrate and kill the organism at the root, then rinsed gently. The roof comes out clean because the growth is dead — not because we sanded it off with water.
> Tile-specific process, not one nozzle for everything
An S-tile roof and a flat tile roof fail in different ways. S-tile hides moss down in the curved channels and under the overlaps, so it needs longer dwell time and rinse angles that follow the barrel of the tile. Flat tile grows lichen across the open face, which calls for a stronger surfactant and a slow, even rinse that lifts the dead material without streaking. Shingle takes the lightest touch of the three. We set solution strength, dwell time, and rinse technique to the roof in front of us — the two documented San Jose jobs further down this page show that difference on real houses.
> Zinc treatment for a longer clean
After the wash, we offer zinc treatment as an add-on: zinc sulfate solution sprayed across the tile, or zinc strips fastened along the ridge. Either way, each rain releases zinc ions that wash down the roof and stop algae, moss, and lichen from re-establishing. A soft wash alone keeps most San Jose roofs clean for 3 to 5 years; zinc solution pushes that to 5 to 7, and ridge strips keep working for the life of the strip.
> Based in San Jose — this is home turf
Bull Run Exterior Wash operates out of San Jose. No dispatch center, no crew driving in from another county, no travel fees. When you call, you reach the people doing the work, and same-day estimates are the norm because we are already here. We serve the South Bay, San Mateo County and lower Alameda County — and San Jose roofs are the ones we clean most.
Want a free San Jose roof estimate? We scope every roof in person — tile profile, pitch, and growth density set the plan, and the number we quote is the number you pay.
