What decides how quickly moss comes back
Moss needs moisture and shade. Anything that keeps your roof damp for longer will bring it back sooner. In Tyrone and Fermanagh we have plenty of rain and mild, damp weather for much of the year, so growth is faster here than in drier parts of the UK.
- ✓Which way the roof faces: north-facing slopes stay damp longest
- ✓Trees and hedges nearby: shade plus leaf litter and spores
- ✓Exposure: open, windy sites dry out quicker than sheltered ones
- ✓Tile type: rough concrete tiles give moss more grip than smooth tiles
- ✓Whether a biocide treatment was applied after the last clean
Signs it is time for a roof clean
Rather than going by the calendar, go by what you can see. Raised green cushions of moss, especially along the lower courses and around chimneys, are the clearest sign. Moss clumps lying on paths or patios after windy weather, gutters filling up quickly, or water overflowing from the gutters in heavy rain all suggest the roof needs attention. Black streaks and widespread lichen are also worth getting looked at.
A sensible approach
It also helps to look at the roof at the same time each year, ideally in late winter or early spring when moss is at its most visible. Taking a photo from the same spot each year makes it easy to see whether growth is speeding up. If you notice moss appearing faster than before, it may be worth trimming nearby trees or asking for a biocide treatment at your next clean.
For many homes, an annual look at the roof from the ground is enough to decide. If moss is just starting to appear, it can wait. If it is building up on the lower edges and around features like chimneys and valleys, it is worth booking a clean before it gets thick, because a lighter clean is quicker and leaves less debris. Some customers prefer to book a check every few years so the roof never gets bad.
How to stretch the time between cleans
A biocide treatment after cleaning helps slow regrowth by dealing with the spores left behind. Cutting back overhanging branches allows sunlight and wind to dry the roof out after rain. Keeping gutters clear prevents moss gaining a foothold along the bottom edge. None of these stop moss entirely in our climate, but together they make a noticeable difference.
Selling or improving your home?
Many people time a roof clean around other work, such as before putting a house on the market, before or after painting the outside, or after having windows or fascias replaced. A clean roof and clean walls make a big difference to how a property looks in photos and from the road.
Frequently asked questions
Is there a standard number of years between roof cleans?
No. It depends on orientation, tree cover, exposure, tile type and whether a treatment was applied.
Should I wait until the moss is really bad?
It is usually better not to. A lighter clean is quicker and leaves less debris in your gutters.
Why does one side of my roof have more moss?
The shaded side, usually north-facing, stays damp longer, which moss prefers.
Can you tell me if my roof needs cleaning yet?
Yes. Send us photos and we will give you an honest view.