Moss from roof tiles
As roof moss loosens, rain carries clumps into the gutter. It can form a dense, wet mass that is much harder to shift than loose leaves.
CLEAN IT CAMBRIDGE · GUTTER CLEANING ADVICE
Why do gutters get blocked? And why does it matter?
A handful of leaves might seem harmless. But when moss, roots and debris prevent rainwater escaping, the consequences can reach well beyond the gutter.
From recurring blockages to overflowing gullies and damp walls, here’s what we’ve learned from cleaning gutters around Cambridge.
Most gutter problems develop quietly. A few pieces of moss fall from the roof. Leaves collect around an outlet. Rain washes grit into the channel. Months later, water starts spilling over the edge — sometimes even though the rest of the gutter looks relatively clear.
This guide explains the causes, the warning signs and what a thorough professional clean involves, drawing on the problems we regularly encounter around Cambridge.
01 / Understanding the causes
It's rarely just fallen leaves.
Leaves are only one part of the story. Gutters also collect material from the roof itself — and some of the most persistent obstructions are hidden at the outlet.
Leaves and twigs
Nearby trees can deposit large amounts of debris in a short period. Twigs can lodge across narrow outlets and trap further material.
Grit and roof mortar
Silt and sand settle at the bottom of the channel. Loose mortar from ridges, valleys or pointing can create surprisingly heavy obstructions.
Plants and grass
When organic debris stays damp, seeds can germinate. Visible plants are often a sign that the gutter has been holding material for some time.
Downpipes and diverters
Rainwater diverters and tight bends can catch debris inside a downpipe. The blockage may be invisible from the ground and from the gutter above.
Falls, joints and fittings
A gutter that slopes the wrong way can hold standing water and sediment. A leaking joint can cause dripping even when the gutter itself is clean.
Real examples · Clean It Cambridge photographs
Six different ways gutters become blocked.
These are actual blockages we have encountered. Notice how different the material looks — and how easily a small outlet or downpipe can become the critical restriction.
The blocked downpipe is particularly important: clearing the visible gutter alone may not restore drainage if water cannot pass through the outlet or pipe.
A gutter can become a garden
When debris becomes soil.
Wet leaves and moss break down into a growing medium. Seeds arrive on the wind or from birds, then take root. By the time grass or weeds are visible above the gutter, the drainage channel may already be substantially obstructed.
We've also found unexpected objects in gutters — including Nerf darts, firework sticks and even a Barbie doll. Almost anything that lodges near an outlet can begin a blockage.
02 / Recurring problems
Why do some gutters keep blocking?
Repeated blockages are often a symptom of the surrounding conditions, not just how recently the gutter was cleaned. A mossy roof continually sheds material. Trees can refill a channel each autumn. Poor falls leave sediment behind.
We also encounter rainwater diverters that catch debris part-way down a downpipe. The gutter above may be empty, yet water still cannot escape freely.
A gutter can be clear along most of its length and still overflow at one blocked outlet.
That is why inspecting the outlet and checking for underlying defects matters. Cleaning removes debris; it does not automatically repair an incorrectly sloped gutter or a worn joint.
03 / What can happen
When rainwater goes the wrong way, the consequences can be costly.
A blocked gutter is not simply an untidy roofline. During heavy rain, large amounts of water can be directed onto parts of a building or garden that were never designed to receive it.
Damp walls and internal moisture
Repeated overflow can saturate brickwork or render. Depending on the building, its condition and the source of the moisture, this can contribute to penetrating damp, damaged plaster and mould indoors. Damp should be properly investigated rather than automatically blamed on gutters.
Rotting timber and damaged finishes
Water running behind or over the gutter can repeatedly wet fascias, soffits, window frames and painted timber. Over time, paint may fail and vulnerable wood may decay.
Staining and deterioration
Persistent streams down walls can leave staining, encourage algae growth and worsen existing defects in pointing, render or masonry. In freezing weather, trapped water can add to deterioration in susceptible areas.
Washed-away soil and paving problems
When a blocked gully or overflowing downpipe discharges water at ground level, concentrated flow can scour soil, wash away gravel or bedding material and undermine the edges of paths or paving. Persistent pooling near a building also deserves investigation.
Water collecting near the building
Gutters and downpipes are intended to direct rainwater towards suitable drainage. Overflow can instead concentrate it beside external walls, entrances and foundations, increasing the risk of local flooding or moisture problems.
Leaks that cleaning won't cure
Not every drip is caused by a blockage. Split fittings, worn seals, leaking joints and gutters with an incorrect fall can continue to leak after debris has been removed.
The important question isn't only whether the gutter is clear — it's where the rainwater goes next.
Warning signs worth checking
- Water spilling over a gutter edge or corner during rain
- Persistent wet patches or green staining on exterior walls
- Overflowing ground-level gullies or water backing up around a downpipe
- Soil or gravel being washed away, or water pooling beside paving
- Dripping joints or standing water even after the gutter has been cleared
04 / Professional cleaning explained
What actually happens during a thorough clean?
The aim is not simply to remove what can be seen from the ground. It's to establish where the debris is, clear the drainage route and check the result.
- Inspect with a cameraWe inspect the gutters to see the debris, identify problem areas and assess the outlets.
- Remove debris with a ground-based vacuumMoss, leaves, silt and other loose material are removed from inside the guttering.
- Clear the downpipe outletsParticular attention is paid to the places where material can lodge and restrict the flow.
- Check the cleaned guttersWe use the camera to check the result and test water flow where practical.
- Explain any findingsWe can provide a report highlighting issues such as leaking joints, roof mortar falling into gutters or sections that may need monitoring or repair.
A view from inside the gutter
1 min 34 sec · Camera attached to the gutter-vacuum nozzle, showing the cleaning process from the point of work.
A wider view of the work
25 sec · Drone footage of gutter cleaning at a large country house.
05 / Knowing the limits
Where gutter cleaning ends and drainage work begins.
We can usually remove debris from the roof gutters, clear the outlets and empty accessible downpipes down to ground level. We use camera inspection to check the guttering and can test water flow where practical.
But the drainage system doesn't necessarily end at the bottom of the downpipe. Water may pass into a ground-level gully, buried pipe or underground soakaway. A blockage or break below ground can cause water to back up even when the gutters above are completely clear.
What we can usually help with
- Removing moss, leaves and debris from roof gutters
- Clearing accessible outlets and downpipes to ground level
- Camera checks before and after cleaning
- Identifying visible problems and reporting our findings
- Minor leaking gutter-joint repairs where appropriate
What needs a drainage specialist
We don't excavate, repair or replace broken underground drainage pipes, or diagnose and repair buried soakaways. If water still backs up at ground level after the accessible guttering and downpipe are clear, the underground drainage may need a specialist investigation, such as a drain CCTV survey.
06 / A closer look
Before and after clearing a gutter.
The visible difference is satisfying, but the more important result is a clear route for rainwater to reach the outlet.
DebrisCleared07 / Prevention
Are gutter guards worth fitting?
Gutter guards sound like a permanent solution, but in our experience they often create more problems than they solve. They can stop larger leaves while allowing smaller material through. Debris can also collect on or become caught in the guard, making the gutter harder to empty when maintenance is needed.
Downpipe baskets can be useful in certain situations. The trade-off is where debris accumulates: the basket may stop material entering the pipe, but it can itself become blocked at the outlet.
There is no universal answer. Roof moss, nearby trees, gutter design and ease of future access all matter. A system that can be inspected and cleaned is often preferable to one that promises to need no maintenance.
A guard may change where the blockage happens rather than eliminate the need for cleaning.
The most reliable prevention is to understand what is entering the gutter, check the drainage points and maintain the system at intervals suited to the property.
08 / Seasonal guide
When should gutters be cleaned?
For most homes, once a year after the autumn leaves have fallen is a sensible starting point. Properties beneath trees, or with roofs that shed significant moss, may need attention more often.
Select a season to see what to watch for throughout the year.
November – December
Late autumn · The main maintenance window
Once the leaves have finished falling, clear accumulated debris once the main leaf fall has finished. The exact timing depends on the trees around your property.
09 / Understanding the terminology
Gutter emptying isn't the same as cleaning the outside.
These are two different kinds of maintenance, and it's useful to know which one you need.
Gutter Care
Removing debris from inside the gutters and clearing outlets to restore drainage. This addresses the functional problem of rainwater being unable to flow away.
Gutter Restore
Gutter emptying plus cleaning the visible exterior guttering, fascias and soffits. This deals with drainage and the appearance of the roofline.
Minor leaking-joint repairs may be possible where appropriate. Cleaning does not correct every defect or guarantee that worn components will stop leaking.
10 / Practical questions
Questions homeowners often ask.
How can I tell if the gutters are blocked?
Look for overflow during rainfall, visible debris or plants, or persistent damp patches below a section. Some obstructions — especially at outlets and diverters — are only evident during inspection.
Will clearing a gutter fix a leak?
It may solve overflowing caused by a blockage, but a leaking joint, damaged fitting or incorrect fall is a separate issue that may need repair.
Can I clean gutters myself?
Some low, safely accessible gutters may be manageable, but working at height brings significant risks. Avoid leaning from ladders or attempting to reach difficult sections; professional ground-based equipment can often reduce the need to work at height.
How often should I arrange a clean?
Annually after leaf fall is a good general starting point. Heavy tree cover, roof moss and known problem outlets can justify more frequent checks.
Why does a gutter overflow even when it looks empty?
The downpipe outlet, a bend or a rainwater diverter may be blocked, or the gutter may not have the correct fall. An inspection can help identify the cause.