The short answer
A polycarbonate conservatory roof typically lasts about ten years according to HomeBuilding, and ten to fifteen according to The Eco Experts. These are typical figures, not promises. A sunny aspect, thin cheap sheets, poor sealing and neglect shorten the life, while good sheets, sound seals and regular cleaning stretch it. Clouding, brittleness, leaks and cracks all show that replacement is due.
What the published figures say
Polycarbonate is the plastic glazing used on many conservatory roofs, usually as multiwall sheet: two thin skins held apart by internal ribs, which trap air and give some insulation. It is light, cheap and easy to fit, and its life is shorter than that of the other main roof options.
HomeBuilding, in its April 2024 guide to conservatory roof replacement costs, puts a polycarbonate roof at about ten years. The Eco Experts, in a guide updated in the same month, give ten to fifteen. Those two sources are close enough to give a working range, and we would treat it as a typical span rather than a guarantee. Neither says that a roof will fail on a given day, and plenty of installations fall either side.
The same sources show how polycarbonate compares. HomeBuilding reports a glass conservatory roof at over thirty years and a tiled one at over fifty, while a solid roof comes out near fifty years or longer in The Eco Experts. If you are weighing a replacement, that gap in lifespan is a large part of why people move up from polycarbonate when they renew.
What shortens the life of a sheet
Several things set where a given roof falls in that range.
- Sun exposure. A south-facing roof takes the most ultraviolet light and heat. Sheets weather faster where they bake all summer.
- Sheet quality. Cheaper, thinner sheet with a weaker protective coating on the outer face breaks down sooner than a better-specified one.
- The seals. Sheets sit in glazing bars and rely on gaskets, closure strips and end sealing. When those fail, water gets into the channels and the roof starts to leak and stain from the inside.
- Thermal movement. Plastic expands and contracts more than the frame around it. A poor fit leaves the sheet squeezed or rattling, and fixings loosen with years of that movement.
- Cleaning habits. Harsh scrubbing or a pressure jet damages the surface. A jet wash scores the outer face, and plastic glazing is softer than tile.
- Trees and debris. Overhanging branches, leaf litter in the bars and green growth along the edges all keep the roof damp and hasten wear.
Signs the sheets are failing
Polycarbonate gives plenty of warning. The common signs are these.
- Yellowing or cloudiness. Clear sheets go milky or dull and let less light through.
- Green or black marks inside the cells. Algae or dirt that gets into the ribs of a multiwall sheet cannot be reached from outside. Once it is in, cleaning does little.
- Brittleness and cracks. If a sheet cracks when touched, or you find hairline splits near the fixings, the plastic has aged out.
- Sagging or bowing. Sheets pushed out of line can no longer seal against their bars.
- Drips at the joints. New leaks at several joints together are a better indicator of general failure than one drip in one corner.
- A room that has become harder to use. Heat and cold are both worse as the sheets and seals age.
A single cracked sheet in a young roof is a repair. Several of these signs together are a different matter, and our guide to repairing or replacing a conservatory roof helps you weigh up the call.
Can you extend the life of the sheets
Yes, within limits. Maintenance cannot reverse the ageing of the plastic, but it can keep a sound roof going for longer and spot problems while they are cheap.
Clean the roof gently with warm water, mild washing-up liquid and a soft brush. Work from the ridge down and rinse well. Keep gutters and the gaps along the edges clear so water drains instead of standing. Check the end caps and sealing strips at the eaves, where water most often finds its way into multiwall sheets. Trim overhanging branches. After a storm, look for lifted sheets, loose fixings and displaced ridge or flashing details.
When a leak does appear, trace it before filling it. Resealing the wrong joint hides the symptom and the water carries on.
Maintenance has a ceiling. Brittle, yellowed and cracked sheet cannot be restored, and thick sealant smeared over a tired roof only adds to the mess. When the plastic itself has gone, it is a replacement job.
What to do when the roof is due
You have two basic routes. The first is to fit new polycarbonate in the existing frame, which is the quickest and cheapest option when the glazing bars and frame are sound. Our guide to replacing polycarbonate sheets covers that job.
The second is to change the roof type altogether, to glass, to a solid roof with insulation, or to a tiled roof. This changes the weight on the frame, may call for structural work, and brings in more regulation. Going solid triggers a Building Regulations application, which the page on conservatory roof regulations walks through.
Either way, the timing and the sequence of the work matter, and the page on how long a conservatory roof replacement takes explains what affects them.
Sorting out what you actually have
Plenty of owners do not know what their roof is made of. Polycarbonate looks like a stiff, slightly flexible plastic with a ribbed cross-section at the cut edge. Glass is heavier, clearer and noisier to tap. Anything in between may be a laminated or coated unit. If you are unsure, a photograph of the inside, the outside and a cut or exposed edge will answer it.
The survey itself is free, and the photographs we take show your conservatory rather than a stock example. A written fixed price follows for the route you pick. If you are leaning towards new sheets, ask what thickness is proposed and whether the outer face carries UV protection. The first page to read for the whole picture is conservatory roof replacement.
