At a glance
A leaking gutter is one of those small problems that becomes a significant one if ignored. Water running down a wall rather than through the downpipe causes damp patches internally, staining and erosion externally, and over time softens fascia boards and causes rot that is far more expensive to repair than the original gutter fault. The majority of leaking gutters in UK homes are caused by blockages, failed joint sealant or sagging sections – all of which can be repaired in a morning by any competent homeowner with a ladder and a few pounds worth of materials.
UPVC guttering – the white or black plastic system fitted to most UK homes built after the 1970s – is particularly easy to work on. The sections clip together, joints are accessible without specialist tools, and replacement parts are widely available from all builders’ merchants. Older cast iron guttering requires a different approach and is worth consulting a professional about if the system is extensive or the joints are difficult to access. The same systematic diagnosis approach applies to other water-related repairs around the home – persistent damp on an internal wall as described in our guide to fixing damp walls often traces back to an external gutter fault as its source.
Diagnosing where it is leaking
The best time to diagnose a leaking gutter is during or immediately after rain, when the leak is active. Use binoculars from ground level first – in many cases you can see water dripping from a specific joint or running down the fascia from a clear point before committing to ladder work. Note where the drip originates relative to the nearest joint, bracket or end cap.
If rain is not imminent, use a garden hose to run water into the gutter from the high end and watch for drips from ground level. This replicates rainfall well enough to identify active leak points and is much safer than inspecting from a ladder during actual rainfall.
Clearing blockages
Clear gutters at least once a year – twice if there are trees overhanging the roof. In autumn, leaves accumulate rapidly and a single tree can block gutters in a matter of weeks. Use a trowel or purpose-made gutter scoop to remove accumulated debris, working towards the downpipe. Bag the material and dispose of it – do not push debris into the downpipe. Finish by running a hose through the full length of gutter to check flow and flush small particles through the downpipe.
If the downpipe is blocked, a drain rod pushed down from the top or up from the bottom with a twisting motion dislodges most blockages. A blocked gutter outlet – the point where the gutter drains into the downpipe – is a common fault and can be cleared with a gloved hand or trowel. Fit leaf guards to the downpipe opening to prevent future blockages without impeding water flow.
Check the gutter fall before blaming a joint for pooling water. Gutters must slope slightly toward the downpipe – approximately 3mm of fall per metre run. If a section of gutter holds standing water after rain, the fall is incorrect and needs correcting by adjusting the brackets rather than adding sealant. A gutter with incorrect fall never drains properly regardless of how well the joints are sealed.
Resealing leaking joints
UPVC gutter joints use either a rubber seal within a union piece, or a socket and spigot joint sealed with gutter sealant. To reseal a union joint, unclip the gutter section from the union, clean the rubber seal and the gutter ends thoroughly with a cloth and white spirit, inspect the seal – if it is cracked, brittle or distorted, replace it with a new seal of the matching profile. Reassemble and test.
For a permanently sealed joint that has failed, cut away the old sealant with a craft knife, clean the surfaces with white spirit and apply fresh waterproof gutter sealant. Use sealant specifically formulated for gutters rather than general silicone – gutter sealant remains flexible as the guttering expands and contracts with temperature changes, while standard silicone cracks. Allow to cure fully – typically 24 hours – before testing with water.
Sagging gutters and brackets
A gutter that has pulled away from the fascia board causes water to run behind it onto the timber rather than into the gutter. This is caused by a failed or loose bracket. To fix, remove the gutter section, replace the bracket – screwing into sound timber with stainless steel screws rather than reusing the old holes which may be stripped – and rehang the gutter. If the fascia board itself is soft or rotten, it must be replaced before any gutter work will hold permanently. Rotten fascia boards are also a route for moisture into the roof structure and should not be deferred.
Replacing a damaged section
UPVC gutter sections are sold by profile and size – the most common UK profiles are half-round and square. Measure the damaged section and take a piece of the old gutter to a builders’ merchant to match the profile exactly before buying replacement sections. To remove a damaged section, unclip it from the union joints at each end and unscrew any brackets along its length. Fit the replacement in reverse order, applying fresh sealant to joints and checking the fall with a spirit level before final fixing.
Downpipe problems
A cracked downpipe section or a failed joint between sections is repaired in the same way as gutter joints – clean, apply appropriate sealant and allow to cure. A downpipe that has pulled away from the wall needs the fixing bracket replacing – the fixing should go into masonry with a suitable wall plug and screw rather than into the render alone. Underground drainage connections at the base of the downpipe can become blocked with silt over time; if the downpipe empties correctly but the surrounding ground floods during heavy rain, the underground drain may need rodding or jetting.
When to call a professional
DIY gutter repair is appropriate for all single-storey work and for accessible first-floor guttering from a domestic ladder. Call a professional for guttering above first floor level, for cast iron guttering on older properties where joints are lead-caulked, for any work that requires working from a roof rather than a ladder, or where the fascia and soffit boards need replacing. Scaffold or tower scaffold is required for safe access above first floor level and the cost of hiring it often makes professional replacement the more economical option at that height.
Never lean a ladder directly against UPVC guttering. Even a brief contact point from a ladder can crack or deform UPVC guttering. Always use a ladder stand-off (ladder stay) that positions the top of the ladder against the wall rather than the gutter, or use a ladder with a specialist gutter hook that clips to the gutter rim to spread the load properly. This is the most common cause of gutter damage during routine maintenance.
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