Blocked gutter or box gutter: what to do?
By the Toiture Wash team · Updated on 20 October 2026 · 3 min read
Short answer. A box gutter or gutter that overflows is most often blocked at the entrance to the downpipe, by leaves, moss or debris. Do not climb up in the rain: note where the water overflows, and if the gutter can be reached from a stable ladder at ground-floor level, remove by hand whatever blocks the entrance to the downpipe. Above the ground floor, or if the downpipe stays blocked, call a professional.
Finding where it is blocked
Look from the ground, during or just after a shower:
- Water runs over the edge along the whole length: the gutter is full, or its slope towards the downpipe has reversed.
- Water overflows near the downpipe: the entrance to the downpipe is blocked.
- The downpipe overflows at its foot or seeps at a joint: the blockage is in the downpipe, often in a bend.
- Water runs down the facade with no visible overflow: a gutter with a hole, an open joint or a leaking box gutter.
What you can do yourself
Only from a stable ladder, standing on level ground, tied off or held by a second person, and only at ground-floor level:
- Remove by hand, wearing gloves, the leaves and moss that have built up, starting near the downpipe.
- Do not push the debris into the downpipe: take it out.
- Run a garden hose to check that the water flows.
- Fit a downpipe strainer (a small domed grille) at the entrance to the downpipe so that it does not happen again.
To avoid: chemical products poured into the downpipe, a high-pressure jet aimed upwards under the tiles, and any work on a wet roof.
When to call a professional
- the gutter or box gutter is above ground-floor level;
- the downpipe stays blocked after you have cleared the entrance;
- water runs down the facade or comes into the house;
- the box gutter is built in, wide, made of zinc, and you cannot see where the water escapes;
- you want to take the opportunity to clean the roof.
Toiture Wash cleans gutters and box gutters and fits downpipe strainers or gutter mesh. While we are there, our team flushes the downpipes with pressure, but we cannot promise to unblock them. See Gutter and box gutter cleaning.
The risks of a blocked box gutter
- Water on the facade: stains, moss, joints that deteriorate over time.
- Damp in the walls, under the box gutter and at the foot of the house.
- Frost: standing water freezes in winter in the gutter and the downpipe.
- Weight: a hanging gutter full of water and soil can warp or come off.
Stopping it from happening again
- Clean them once a year, after the leaves have fallen: October is when we receive the most requests for gutters.
- Downpipe strainers at the entrance to every downpipe, and a mesh if the house is under trees.
- A roof moss removal when the roof turns green: the moss that comes loose ends up in the gutters.
- Trim back branches that overhang the roof, regularly.
Frequently asked questions
Who pays for gutter cleaning, the tenant or the landlord?
The tenant, for routine maintenance and within the limits of what is accessible: without professional equipment in Brussels, with a reasonably sized ladder in Flanders; in Wallonia, regular cleaning falls to the tenant, unless the parties agree otherwise. Repairs and replacement remain the landlord's. See also Roof moss removal: does the tenant or the landlord pay?
Can a blocked gutter fill my tank with dirty water?
Yes: leaves, moss and sludge go down the downpipe when its entrance is not protected. A downpipe strainer and a filter before the tank limit what gets in. Roof moss removal and your rainwater tank
How much does gutter cleaning cost?
Gutters on their own are priced per metre: €10 per metre excl. VAT; for gutters only, there is no minimum. For work under €1,000 excl. VAT, travel and set-up costs are added: the quote states them. With a roof moss removal, gutter cleaning is included in the price.