Quick answer
How often should gutters be cleaned?
Clean gutters once a year as standard, ideally in late autumn after the leaves have fallen. Increase to twice a year if you have overhanging trees, an older concrete tile roof that sheds moss, three or more storeys, or a history of overflowing.
Clean twice a year if you have…
Overhanging trees
Oak, sycamore and conifer are the worst offenders.
Ageing concrete roof tiles
Very common on Coventry 1930s, 1960s stock; moss sheds constantly.
Three or more storeys
Longer runs, more silt, harder to spot problems from the ground.
A flat-roof extension draining across
Debris concentrates at one outlet.
Signs it needs doing now
Water spilling over the front edge during rain. Plants growing out of the gutter. Green streaks down the wall below an outlet. Dripping at the top of a downpipe. Damp patches inside that line up with a gutter joint.
If any of those are present, don't wait for the annual slot, see what a clean costs for your property type.