Not everything green, grey or black growing on a Hanham roof is the same thing, and knowing the difference matters because moss, lichen and algae behave differently and can call for slightly different treatment. It is common for homeowners to describe any roof growth simply as moss, when in fact a roof might be dealing with one of these, or more often, a combination of all three.
Moss is the most familiar culprit, appearing as a thick, cushion-like green growth that tends to cluster in shaded, damp areas such as north-facing slopes, valleys and around chimneys. It has a distinct three-dimensional, almost furry texture and holds moisture against the tile surface, which is part of why it is the growth most closely linked to longer-term roof problems if left unaddressed.
Algae shows up differently, typically as a black or dark green staining that sits flat against the roof surface rather than forming raised clumps. It is often mistaken for general dirt or soot, but it is a living growth that thrives in damp, humid conditions and can spread across large areas of tile relatively quickly, particularly on roofs that do not get much direct sun.
Lichen is the least common of the three but often the toughest to deal with. It appears as flat, crusty patches, sometimes grey, yellow or pale green, and bonds itself very firmly to the tile surface. Because lichen grows so slowly and attaches so tightly, it can be more resistant to gentle cleaning methods and sometimes takes longer to fully clear than moss or algae.
On many Hanham roofs, particularly older properties or those with mature trees nearby, it is common to see two or even all three of these growing together in different areas of the same roof. A shaded valley might carry thick moss, while a more exposed slope shows algae staining, and a ridge line has patches of lichen that have been slowly establishing for years.
Correctly identifying what is actually growing on a roof, rather than treating everything as the same problem, allows the right approach to be used, and a proper assessment before cleaning starts is the best way to make sure the treatment matches what is actually there.
Getting the identification right also affects expectations around how quickly results will show and how long they are likely to last. Algae staining often lifts relatively quickly once treated, giving a fairly immediate visual improvement, whereas established lichen can take longer to fully clear given how firmly it bonds to the tile surface. Knowing which of the three is present, or which combination, helps set a realistic sense of what a Hanham roof clean will achieve and over what kind of timescale.
A close visual inspection, ideally from a safe vantage point rather than climbing onto the roof itself, is usually enough for an experienced roofer to distinguish between the three, though a hands-on assessment during a site visit gives the most reliable picture of what a particular Hanham roof is actually dealing with.
If you are unsure what is growing on your roof in Hanham or how best to deal with it, Brunel Roofing Bristol can take a look and advise on the most suitable way to clean and treat it properly.
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