Water that appears inside a conservatory seldom comes through the spot where you see it. It runs along a glazing bar, tracks down the back of a wall flashing or creeps through the flutes of a polycarbonate sheet before it finally drips onto the floor, so the stain on the ceiling or the puddle by the French doors only tells you roughly where to start looking. Finding the true entry point is most of the work. This guide covers the faults we meet on glazed, polycarbonate and solid conservatory roofs, how to separate a leak from condensation, and how we decide whether a roof is worth repairing.
Trace the water before you touch the sealant
The first mistake people make is squeezing silicone into the nearest gap. Sealant applied to the wrong place can trap water inside a joint and make a slow leak worse, and it makes the next repair harder because the old joint has to be cleaned out first. Start instead by watching the leak. Look at the roof on a dry day, then again while rain is falling, and note which part of the room drips first and how quickly. A leak that starts within minutes of rain beginning is usually a direct opening in the roof. One that appears an hour into a downpour, or only after a long wet spell, is more likely water working through a junction or soaking along a timber.
Check the pattern too. Drips along one glazing bar point to that bar's seal or cap. Staining that follows the wall of the house points to the junction between conservatory and main building. Water at the eaves, beside the gutter, suggests the lower edge of the roof or the gutter itself. A drip in the middle of a large pane of glass or a sheet of polycarbonate, well away from any bar or wall, is more unusual and often means the sheet has cracked or a fixing has gone through it.
From outside, a safe look from the ground or a ladder at the eaves shows a lot: slipped sheets, a gutter full of moss, a ridge cap that has shifted, lead flashing lifted from the wall. Do not walk on a conservatory roof. Glass, polycarbonate and even many solid roofs are not designed to carry a person, and the fall through the roof is a serious one. If the roof needs to be reached, that is a job for a roofer with crawling boards and, on the higher conservatories, scaffold or a tower.
Is it a leak, or is it condensation?
A conservatory is a big sheet of cool surface wrapped around a warm, humid room, so condensation is common and often mistaken for a leak. Cooking, drying washing, houseplants and simply being in the room all add moisture to the air. When that air meets a cold roof it turns to water, which runs down the inside of the glazing and drips from the bars. The giveaway is timing and weather. Condensation forms on cold mornings and cold evenings, whether or not it has rained, and it shows as a film or beads across the whole roof rather than a single path. A leak follows rain and has a clear starting point.
Two other look-alikes catch people out. Misting between the two panes of a sealed glass unit means the edge seal has failed and moist air has got in; the unit is not leaking into the room and the cure is a new unit, not new sealant. Algae and dirt inside the flutes of polycarbonate can also look like water ingress when the sheet is simply dirty from within. Always ask first whether water is coming in, or whether moisture is forming inside, because the two have entirely different cures.
| What you see | Likely cause | Usual remedy |
|---|---|---|
| Drips along one glazing bar in rain | Perished gasket or lifted cap on that bar | Reseal or replace the bar cap and gasket |
| Streaks down the house wall | Failed or poorly set flashing at the abutment | Re-form the flashing and a proper cover strip |
| Wet patch near the gutter | Slipped sheet, blocked gutter or open eaves closure | Refit the sheet, clear and realign the gutter |
| Misting between glass panes | Failed edge seal on a sealed unit | Replace that unit |
| Beads of water across the whole roof on cold mornings | Condensation, not a leak | Ventilate, reduce moisture, consider insulation |
Glazing bars, gaskets and caps
On a glass conservatory roof, panes sit between aluminium or uPVC glazing bars. Inside the bar there is a rubber or synthetic gasket pressed against each pane, and over the top runs a cap that is screwed or clipped down to hold the glass. The cap shields the gasket from sun and weather, but over the years the rubber hardens, shrinks and splits. Once a gasket stops pressing evenly against the glass, water finds the gap and runs down inside the bar to the eaves, or drips out through any hole along its length.
Caps cause their own trouble. Screws work loose as the bar expands and contracts through the seasons, a cap warps in strong sun and no longer sits flat, or a capping end at the ridge or the eaves comes away entirely. Silicone smeared along an old cap seldom lasts, because the surface underneath is dirty and moving. The sound fix is to lift the cap, replace the gasket along the whole run rather than patching one corner, refit a cap that sits properly and use fresh fixings. A conservatory built around the 1990s or early 2000s often has the same age of rubber on every bar, so a leak on one is a warning for the others.
Cracked panes are simpler. A pane that has taken a stone or has stress-cracked from heat is replaced as a unit. Fitting the new one is quick, but the bars either side must be in good order, or you will be back with the same drip in a different place.
Polycarbonate sheets: slipped, split or worn out
Polycarbonate roofs are built from long multi-wall sheets, with parallel channels called flutes running down the slope. The sheets are held by bars or clips, with closure strips at the ridge and eaves, and a coating on the outer face to resist ultraviolet light. A sheet sits in its bars loosely on purpose, because plastic expands and contracts far more than glass or aluminium. Over many summers a sheet can creep downhill, leave its seat and expose a gap at the top. Then rain runs straight in under the cap.
The other common faults are the closure strips and the sheet ends. An open end lets dust, insects and water into the flutes, and the water that settles there grows algae, which turns sheets green and milky. Repeated heating and cooling makes old polycarbonate brittle, and the outer coating wears off, so the plastic yellows, crazes and eventually cracks, often around a fixing. A sheet that is cracked or that has lost its protective face is nearing the end of its life, and we say so rather than recommending another patch. Our page on how long a polycarbonate conservatory roof lasts goes into the ageing in detail.
A slipped sheet that is still sound can be eased back, the closure strips replaced and the caps refixed with correct clips. A brittle roof is a different matter. Taking out a cap on twenty-year-old sheets frequently cracks them as soon as they are disturbed, and then a small repair becomes a large one.
Where the conservatory meets the house
The joint between a conservatory roof and the wall of the house is the single most frequent source of trouble on lean-to roofs and on the back edge of other styles. The roof ends against brickwork, and something has to bridge the gap: lead flashing, a folded aluminium section or a sealed uPVC trim. The covering is meant to turn up the wall (the upstand), and a flashing then laps over that upstand and is tucked into a mortar joint, with the other edge dressed over the roof.
On many older conservatories the flashing was fixed by smearing a bead of mastic along the wall and nothing more. Mastic cracks as the wall and roof move apart in different weather. Where lead was used, it can be lifted by wind, split by repeated movement or left unprotected where the mortar behind it has crumbled. Water then runs behind the flashing and down the back of the frame. A cavity tray or a proper damp-proof detail should catch water inside the house wall, and when it is missing or damaged the stain may appear well below the actual opening.
Repair means re-forming the junction. We cut a new chase into sound mortar, fit fresh lead or an equivalent flashing, dress it over the upstand and point it up, then cover or seal the roof side properly. We have a separate page on a conservatory leaking where it meets the house if that is where your water appears.
Gutters, eaves and the lower edge
Conservatory gutters are small and sit close to the roof. Leaves, moss and roof debris block them quickly, and when the gutter overflows, water spills back into the eaves beam or over the front of the frame, which can look exactly like a roof leak from inside. A gutter that has dropped out of line holds water in the lower stretch and spills at the joints. Sagging brackets, split joints and cracked downpipe connections all turn up here.
The eaves beam itself deserves a look. It is the structural piece at the bottom of the roof that carries the glazing bars, and if water has been getting at it for years the timber or the cladding around it may be wet or soft. Rot in that beam changes the answer from a seal to a rebuild, because the roof depends on it.
Gutter faults are cheap to put right when caught early. Ignoring them for a few winters is how a ten-minute clearance becomes a rotten fascia or beam.
Repair or replace: how we decide
Most of the repairs above are worth doing when the roof beneath them is sound. A good frame with cracked caps, perished gaskets or a failed flashing is a repair job, and it makes sense to spend a modest sum and keep the roof for many more seasons. We tell you so on the survey, with photographs of what we found, and we do not push a new roof on a roof that has years left in it. Our guide to repairing a conservatory roof rather than replacing it sets out the cases in more detail.
Replacement comes into view when several things stack up: brittle, crazed sheets; bars whose gaskets have failed along their whole length; a rotten eaves beam; or a roof that is also too hot in summer and too cold in winter. Swapping glass or plastic for a solid tiled roof is notifiable work under the Building Regulations, since the existing frame and base have to be shown capable of carrying the added load. The typical UK range reported for a solid tiled conservatory roof is £6,100 to £15,000 overall, with the rate put at £650 to £1,200 for each square metre, and the written quote comes after the survey, not before it. Our overview of conservatory roof replacement in Basingstoke covers the options.
What our survey checks on a leaking conservatory
When we visit, we look at the roof from outside with the right access, and from inside with the room in front of us. We check each bar cap and gasket run, the sheet seats and closures, the abutment flashing, the gutter and the eaves beam, and we photograph every fault so you can see it on your own roof. A hose test, working from the bottom of the roof upwards, finds an entry point that rain has not shown us.
You then get a written report and a fixed quote for the repair that works, or an honest recommendation to replace if the roof is spent. Repair and replacement work carries a written 10-year guarantee on our workmanship, and the site is left clear when we finish. A leaking conservatory is worth looking at before the next wet week: ring 01256 213956, or drop us a line on WhatsApp.
