5 Signs Your Hampshire Roof Needs a Clean

Most Hampshire roofs we’re called to clean have been showing signs for 2–3 years before the call. Here’s what to watch for — in order of severity.

1. Visible Black Streaks

The classic early warning. Streaks of dark grey or black running vertically down concrete tiles, particularly on north-facing slopes. The cause is a specific algae (Gloeocapsa magma) that feeds on limestone filler in concrete tiles. Cosmetic at first — but every year it’s left, the algae locks more deeply into the tile surface.

2. Green Patches Visible from the Road

Once you can see green from ground level, you’re looking at established moss colonies. Light coverage doesn’t damage tiles in the short term, but moss holds water against the tile, accelerating freeze-thaw damage in winter. Heavy moss visible from across the street usually means 5+ years of build-up — time to act.

3. Moss in the Gutters

If you’re finding moss debris in the gutters during routine cleaning, the roof itself has significantly more. The pieces that fall into the gutters are the loose, dying outer growth — the bulk of the colony is still on the tiles. This is a 12-month warning sign.

4. Stained Walls Below the Gutters

Dark streaks running down the walls below the gutter line aren’t just rain marks — they’re algae spores washed off the roof. If the wall is stained, the roof is the source. Cleaning the wall without cleaning the roof is a temporary fix.

5. Tile Edge Damage

The serious one. Once moss has been on tiles for 7–10 years, you start to see tile edge chipping, lifted ridge mortar, and the occasional cracked tile. This is the point where roof cleaning becomes urgent maintenance rather than cosmetic. Beyond a certain damage threshold, you’re looking at partial tile replacement instead of a clean.

What to Do Next

If you’re seeing 1 or 2 of these signs, you have time — book for next spring/summer. If you’re seeing 3 or more, particularly tile edge damage, we’d recommend an inspection within the next 6 months. Send us a few photos for a free assessment.

Related Reading

When to clean your roof · Pricing guide · Moss removal in detail