Possible causes
- Leaves or silt blocking the run
- Blocked outlet or downpipe
- Gutter sagging between brackets
- Incorrect or lost fall
- Too few or undersized outlets
- Roof valleys concentrating flow
- Damaged or distorted guttering
Observe where it starts
Overflow at one point may show the nearest restriction, a low spot or a concentrated roof-water entry point. Photos during rain can help, provided they are taken safely from ground level.
Do not rely on a bigger gutter alone
Capacity involves gutter profile, fall, outlets and downpipes together. Changing one component without checking the whole path can move the problem elsewhere.