A leaking conservatory roof is easy to notice and hard to pin down. Water gets in at one spot, travels along a bar or a sheet, and falls somewhere else. Painting sealant over the nearest stain often moves the problem a metre along. A proper repair starts with finding where the water goes in, which means working through the roof one junction at a time.
The roof of a conservatory is made of a few parts that each leak in their own way. The ridge is the top edge, where one slope meets another. The box gutter is a hidden channel, often at the eaves or between roof sections. Glazing bars hold the panes or sheets and carry gaskets. The wall abutment is where the roof meets the house. This guide goes through each, then covers when a repair stops making sense. For the quick-fix question, see whether sealant stops conservatory roof leaks. The overall service is on the conservatory roof replacement page.
Tracing the drip back to its source
Water follows the easiest path, and in a conservatory roof that path is usually along the underside of a glazing bar or the face of a rafter. The wet patch on the floor tells you where it landed, not where it came in. The first job is to work back up from the stain.
Dry weather checks
We start from the inside, looking for staining, green or black marks, and tide lines on the bars. These show the route. A line of dirt that stops at a joint is a strong hint. Outside, we look at the ridge, the cappings, the gaskets and the flashing, and at anything that has shifted or split. Leaves and moss in a gutter or a valley hold water against a joint it was never meant to meet.
Wet weather checks
A hosepipe test, working from the bottom of the roof upwards, is the usual way to prove a suspected source. Starting low matters. Water applied at the top runs down over every lower joint and muddies the result. We wet a section for several minutes, wait, then move up. It is slow but it stops guesswork. A leak that appears only in a hard, wind-driven shower, and not in steady rain, points to a gap that opens under pressure, such as a lifted flashing or a poorly seated capping.
We photograph each finding so you can see the fault for yourself, so the pictures show your own roof and not a stock image.
Ridge leaks: cappings, seals and the high joint
The ridge is where the two slopes meet and is the part of the roof most exposed to movement. In a glass or polycarbonate roof the ridge is normally capped with an aluminium or uPVC section that runs the full length, and the cap is sealed to the glazing with gaskets or sealant. In a tiled or solid roof the ridge is finished with ridge tiles, bedded in mortar or held with a dry-fix system.
Glazed roofs
Over time the capping seals shrink and crack, and the cap itself can lift if its fixings loosen. Sunlight makes the plastic gaskets stiff, so they stop following the small seasonal movements of the roof. Water then runs under the cap and drips from the head of a bar. The repair is usually to remove the cap, clean the surfaces, replace the gaskets or fit new seals, and refix the cap. Resealing over a dirty, cracked joint rarely lasts.
Tiled and slate roofs
Ridge tiles are held in place by their bedding and, under the 2014 revision of BS 5534, by mechanical fixings as well, because bedding mortar by itself can no longer be counted on. If bedding has crumbled or tiles have shifted, rain gets underneath. MyBuilder's 2026 guides give typical figures of £300 to £600 for rebuilding the ridge bedding or swapping tiles on a house roof, and £500 to £1,000 for a typical dry ridge job. They are general UK figures for house roofs, not conservatory-specific ones, and not a Supreme Roofing price.
On a solid conservatory roof, the ridge should also be checked from inside the roof structure for any sign that water has got past the tiles and soaked the insulation or the timbers beneath.
Box gutter and valley leaks: the channel you cannot see
A box gutter is a channel built into the roof, often along the junction between a conservatory and the house, or between two roof sections. It handles a large share of the rain that lands on the roof, and it is out of sight from the garden, so faults go unnoticed until water appears indoors. A valley is the V-shaped trough formed where two slopes join in an inward corner. Both can leak, in similar ways.
Blockage and overflow
Leaf litter and moss narrow a box gutter or fill a valley. Water then banks up and finds its way under the edge of the roof covering or over the lip of the lining. A cleaned channel often stops the leak by itself. We clear the debris, check that the outlet runs freely, and flush with water to confirm the flow reaches the downpipe.
Failed linings
Box gutters are lined with lead, a single-ply membrane such as EPDM, or GRP. Each ages differently. Lead can crack at folds where it has been bent repeatedly; MyJobQuote's guide gives correctly installed lead flashing over 80 years, and over 100 for the higher codes, so cracking in lead suggests poor detail or movement rather than age alone. Rubber membranes can pull away at laps and corners. A box gutter laid to poor falls holds pools, and a pool will find every pinhole. Where the lining is torn or the falls are wrong, a patch is a short-term fix. A relined channel, with proper falls and an outlet that is not undersized, is the lasting repair.
Repairing a box gutter often means lifting part of the roof covering beside it. That is why we agree the scope in writing and make sure the access, the relining and the making good are all covered.
Glazing bars, gaskets and polycarbonate sheets
Glazing bars are the aluminium or uPVC sections that run down each slope and carry the glass or sheet. Their cappings hold the glazing down, and the gaskets between bars and glazing form the seal. A leak at a glazing bar normally means a seal has failed, a capping has moved, or the bar's internal drain has clogged.
Why the seals fail
Rubber and plastic gaskets harden and shrink with age and sunlight. Conservatory roofs flex through the day as they heat and cool, and a hard gasket cannot keep up with the movement. The gap that opens is small but enough to let water travel along the bar. Dirt and algae collect in the gap and hold moisture there.
Polycarbonate
With twin-wall sheet, water can also enter through the open ends of the flutes if the end closures have failed, and it then appears as condensation or green growth inside the sheet. Sheets that have cracked or yellowed are near the end of their useful life. The Eco Experts quote about 10 to 15 years for glass or polycarbonate roofs, and HomeBuilding puts a typical polycarbonate roof at 10 years. Our guide to polycarbonate lifespan covers when to stop patching.
Repair routes
Where the glazing is sound, replacing gaskets, refitting cappings and clearing the bar drains often cures it. A single cracked sheet can be swapped. If many seals have failed across the roof, the repair becomes a series of patches, and the price of repeated visits starts to approach the cost of a new roof.
The wall abutment: flashing, cover and movement
The junction at the house wall is a frequent entry point for water, and one of the first places we check. The roof has to be sealed to a wall that does not move at the same rate as the frame.
How the junction is built
The classic detail is a lead flashing, a strip of lead let into a slot (a chase) cut in the wall and shaped down over the top edge of the roof. Lead is soft and can be shaped into the joint. Leadworx names Code 4 as the usual choice where general flashing is needed. Some conservatories use an aluminium or uPVC wall flashing instead, sealed with sealant. Behind either, a cavity tray or damp-proof course should direct any water that gets behind the wall surface out and away.
What goes wrong
Flashings lift where the fixings have loosened. Sealant at the top edge dries, shrinks and pulls from the stone or brick. Pointing around the chase breaks up, especially on soft stone walls. Sometimes the problem is above the junction: a leaking house gutter or downpipe that runs water down the wall and behind the flashing. We check those before blaming the roof.
Checkatrade's repair guide shows Code 5 lead flashing repairs at £50 to £70 per metre, and stepped flashing at £80 to £120 per metre, excluding VAT. Access and condition move the real price. A listed house, or one in a conservation area, calls for a check with the planning team before altering how the roof meets the building.
Repair, reseal or replace?
Not every leak is worth repairing. We look at three things: where the water is coming in, how old and worn the roof is, and what a repair is likely to buy you.
When repair makes sense
A single failed seal, a lifted flashing, a blocked box gutter or one cracked sheet on an otherwise sound roof is a good repair candidate. The work is local, the cost is modest, and the roof has years left. The MyBuilder 2026 guide gives roof repair costs of £150 to £1,500 for roofs generally, with minor repairs running £100 to £300.
When it does not
If seals are failing across the whole roof, the sheets are brittle and discoloured, and the frame is moving, repairs become a rolling bill. A new roof deals with the cause, not each symptom. Polycarbonate replacement is typically £2,000 to £5,000, glass £3,000 to £8,000 and solid £5,000 to £10,000, according to the same MyBuilder guide. That decision is explored in our guide to lightweight tiled roof systems, which are a common answer when the old roof has gone beyond economic repair, and in the roof insulation guide, since a leaking roof is often a cold and noisy one as well.
Whatever route you take, the quote is written after the survey, and a repair carries our 10-year workmanship guarantee, in writing. Send photographs of the stained area and the roof from outside to 01453 933613 or by WhatsApp, and we will say where we would start looking.