Conservatory Roof Leaking? Causes and Repairs

Start inside and work outwards. Look for the highest point where you can see water or a stain, because a drip low down on the glass has usually run down from higher up. Note where it appears, and whether it only shows in a particular wind direction. Rain driven by a south-westerly into one side of the roof and none into the other tells you a great deal, so write the wind direction down next to the date.

How do you test a conservatory roof safely?

The sensible method needs two people. One stays inside with a torch; the other runs a hose over the roof, starting low and working upwards, a section at a time, with a pause between each so the water has time to show. When the drip starts, the section just wetted is the suspect. Do not do this on a roof you have to climb onto to reach. Never walk on a glass or polycarbonate roof, because it will not take your weight and a fall through it can be serious.

• Stains in a straight line down from a bar point to the bar or its seals.
• Dampness along the house wall points to the flashing.
• Water at the eaves, or marks on the frame outside, point to the gutter.
• A wet patch beneath the ridge points to the ridge joint.

Could it be condensation instead?

Perhaps. If the water appears on dry days across a wide area of glass, it is condensation, and a sealant gun will not fix it. The condensation guide on this site tells the two apart, and it is worth reading before anything is resealed.

Think of the ridge as the roof's spine, the high line at which two slopes come together, and on a lean-to conservatory the highest point is instead the junction with the house wall. A hipped or Victorian shape has ridges and hips, the sloping lines at the corners, and every point where slopes join is a seam that must stay sealed.

Why does the ridge leak?

In a glazed roof the ridge often has a cap or cresting that covers the top edge of the glazing and carries a seal under it. These seals shrink and crack with age and sun, and the fixings that hold the cap can loosen as the frame moves through the seasons. Once the seal has failed, rain gets under the cap and runs down inside the bars. The first sign indoors is often a stain at the top of a rafter or a drip at the apex.

In a roof with a tiled ridge, the failure is different. Bedded ridge tiles can lose their mortar, and Marley explains that tiles bedded along a ridge or hip need mechanical fixings, because mortar on its own is not trusted to hold them in a gale. Ridge tiles on a conservatory with a solid roof are a job for a roofer, not a sealant tube.

Resealing a ridge works where the cap is sound and only the seal has failed. If the cap is bent, corroded or no longer sits flat, the honest answer is that it needs replacing, and a bead of silicone will hold for a few weeks at most. We photograph the ridge from the ladder so you see what we see.

This is the commonest source. The panels of a glazed or polycarbonate roof sit between bars, and the join between a bar and a panel is sealed by a rubber gasket, a tape or a compression cap. Each of those is a material that ages.

What goes wrong with the bars?

The gasket dries and shrinks away from the glass. Caps lift where screws have worked loose. On timber bars, wet rot starts at the end grain and the seal loses its grip on soft wood. Aluminium bars have a built-in channel that carries water down the bar and out at the eaves, and if that channel blocks with dirt or moss, water backs up and spills over into the room. Cleaning the channel is a first, cheap job, and it solves a surprising number of drips.

What about polycarbonate sheets?

A polycarbonate sheet is held by bars, and its ends are closed with tape or a profile. Sheets that have moved can leave a gap at the bar, and sheets that have gone brittle can crack. Published typical lifespans run from about 10 years (HomeBuilding, for polycarbonate) to 10 to 15 years (The Eco Experts, for glass or polycarbonate), so an older sheet may be near the end. A single cracked sheet can still be replaced alone, and replacing one panel is a smaller job than replacing the roof.

Repair means new gaskets, new caps and sealant used sparingly in the right places, and sealant is only one of the tools. Thick sealant smeared over every bar is a sign the roof has been patched many times, and it often traps water behind it.

The roof of a conservatory ends against the house, and that line is weatherproofed by flashing, a strip of metal, almost always lead, tucked into the brickwork above and laid over the roof below. Where the roof is glazed, a flashing lap or a gasket runs along the glass. The detail is hard to get right, and it is a frequent culprit in older conservatories.

What makes a flashing fail?

Two things, mostly. The first is the cover mortar. Lead is often tucked into a groove cut in a mortar joint and pointed in, and the mortar cracks and falls out, leaving a gap. The second is movement. A conservatory frame and a house wall move differently as the seasons change, and an inflexible fillet of cement or sealant along the joint cracks within a year or two.

Each grade of lead sheet is named by a code number. In Royston Lead's brochure, code 4 (1.80mm) is listed for soakers and flashings, for dormers and for pitched valley gutters, while code 5 (2.24mm) is listed for flashings and heavier details. A soaker is a little lead sheet slipped in beneath the tiles. MyJobQuote says lead can last for over 80 years, so a lead flashing that has failed early has usually lost its fixing or its pointing, rather than worn out.

The repair is to rake out the joint, dress the lead in properly, and point or seal it with the right material. If the old lead has been replaced with self-adhesive tape, that is a stopgap. Our page on conservatory roof wall flashing goes into the detail.

A gutter that overflows will make the conservatory look as though the roof is leaking, because the water runs behind the gutter, down the frame, and in through the wall plate. A gutter that has dropped, or been fixed with the wrong fall, will hold water instead of passing it on.

How much fall should a conservatory gutter have?

Brett Martin's guidance for rainwater guttering is a fall of 1mm for every 600mm along the run towards the outlet. A small amount of fall, but it is the difference between a gutter that drains and one that stands. Conservatory gutters are short, which makes a slight sag easy to miss and easy to correct.

• Look for rust, moss or green growth at the low end of the gutter.
• Check whether the downpipe takes water away freely or backs up.
• Look for staining on the wall behind the gutter after rain.

Blocked gutters are the simplest leak to put right, and the roof gets blamed for it every autumn. Clearing leaves, moss and sediment from the gutter and the outlet costs little. If the gutter is cracked at its joints, it can be re-sealed or replaced as a short run.

Is the eaves detail part of it?

Yes. Where the roof meets the frame at the eaves, there is usually a drip or a trim that throws water into the gutter. If it is bent or missing, water creeps back under the roof and into the room. That is a small repair, but it only shows when someone looks for it with a ladder and a torch.

A conservatory roof with one failed seal, one cracked sheet or a blocked gutter is a repair job, and it should be priced as one. A roof with failing seals across most of its bars, sheets that are stained inside, a frame that is rotting, or a history of repairs that have each held for less than a year has reached the point where repairing it again costs more than it saves.

What decides the price of a repair?

How many joints are involved, the access for a ladder or a platform, whether lead or timber needs replacing, whether the frame is sound, and whether the leak has already damaged anything beneath it. The survey tells us which. MyJobQuote gives the average roof repair as around £650 in 2026, a general figure for roofs of every sort, and your own conservatory may be higher or lower.

When is a new roof the better buy?

When the repairs list is longer than the roof's remaining life. Our guide to repairing or replacing a conservatory roof sets out the signs, and our page on conservatory roof replacement cost shows typical UK ranges for a new one.

Where a storm caused the damage, the insurer hears about it first, and photos and receipts are kept for the claim. Our page on conservatory roof insurance has the steps. On our side, the first job is making the roof safe.

For a leak you can see, the quickest route is a survey. The visit finds the source, puts photos of it in front of you, and ends with a single written figure for the repair that lasts.