Polycarbonate conservatory roofs usually last about 10 to 20 years before they yellow, turn brittle and start to leak, and sealed glass units often mist up after 15 to 25 years. If yours shows two or more of the signs below, such as repeat leaks, heavy condensation or a room you cannot use for half the year, replacement usually beats another repair.
How long conservatory roofs last
Most conservatories built in the 1990s and 2000s have a polycarbonate roof, usually 16 mm or 25 mm thick. Sunlight slowly breaks down the plastic, so the sheets go cloudy, then yellow, then brittle. In most homes that takes somewhere between 10 and 20 years, with south facing roofs ageing fastest.
Glass roofs last longer as a material, but each sealed unit relies on a seal round its edge. When the seal fails, moisture gets between the panes and the unit mists up from the inside. That tends to start after 15 to 25 years. Older glass roofs fitted before 2002 are also poor insulators, with a U-value of about 2.8.
Age alone is not a reason to replace a roof. The signs below tell you more about whether yours is near the end.
The nine signs
1. Yellow, cloudy or brittle polycarbonate
Discolouration means the sheet has started to break down. Brittle sheets crack when a branch or a hailstone lands on them, and cracked sheets let water into the flutes. Once the plastic has yellowed, cleaning will not bring it back.
2. Green or black growth inside the flutes
Polycarbonate is made of hollow channels. If the tape or end caps at the bottom edge have failed, water and dirt get in and algae grows where you cannot reach it. It is a sign the seals are gone, not just a cleaning job.
3. Leaks that come back after each repair
A single leak at one joint is often a simple fix. Leaks that return, or move from one spot to another, usually mean the gaskets and seals along the roof bars have aged together. Our guide to a leaking conservatory roof covers how to find the source.
4. Condensation dripping on cold mornings
Polycarbonate and older glass are cold on the inside surface, so warm moist air from the room condenses on them and drips. Some condensation is normal on a single cold night. Water running down the walls most mornings from October to March means the roof is losing a lot of heat.
5. Misted glass units
Fog or droplets between the two panes of a glass roof unit mean the seal has failed. The unit can be replaced on its own, but if several are going at once, the others are usually not far behind.
6. Sheets slipping towards the gutter
Polycarbonate sheets that have slid down leave a gap at the ridge where rain gets in. They can be pushed back and fixed, but slipping often comes back on older roofs where the bar caps and fixings have loosened.
7. A room that is too hot or too cold to use
Conservatories regularly pass 35 to 40°C in summer because direct sun comes straight through the roof. In winter the same roof lets heat straight out. If the room is closed off for more than half the year, the roof is the main reason.
8. Rain so loud you cannot hear the television
Thin polycarbonate drums under heavy rain. It does not mean the roof is failing, but it is one of the most common reasons people replace a roof that is otherwise sound.
9. Sagging bars or a dropped gutter
Roof bars that dip in the middle, or a box gutter that has pulled away from the house wall, point to a structural issue. That needs checking before any new roof goes on. Our guide on whether your frame can take a solid roof explains what to look for.
Quick checklist: repair or replace?
| What you see | Likely cause | Usually the better choice |
|---|---|---|
| One leak at one joint, roof under 10 years old | Failed gasket or blocked gutter | Repair |
| One or two misted glass units | Failed edge seals | Replace those units |
| Yellow or brittle polycarbonate | Sunlight damage to the sheets | Replace the roof |
| Leaks in several places, or leaks that return | Seals ageing across the whole roof | Replace the roof |
| Heavy condensation most winter mornings | Cold inside surface, high heat loss | Replace with an insulated roof |
| Room unused in summer and winter | Roof lets heat in and out too easily | Replace with an insulated roof |
| Sagging bars or a cracked base | Structural movement | Get the structure checked first |
What replacing with like for like gets you
You can put a new polycarbonate roof back on. For a 3 m by 3 m roof that costs around £2,000 to £3,500. New sheets will look clear again, but 25 mm polycarbonate still has a U-value of about 1.6, so the room stays cold in winter and hot in summer, and you are likely to face the same decision again in 10 to 20 years.
Replacing with modern low-e glass costs about £350 to £550 per m², or £3,300 to £5,200 for a 3 m by 3 m roof. Glass with a U-value of 1.0 to 1.2 is much better than old units, but it still lets direct summer sun in.
What an insulated panel roof changes
Our panels have a 75 mm foam core and a U-value of about 0.43. Against 16 mm polycarbonate at 2.3, that cuts heat loss through the roof by about 80%. On a 12 m² roof with 20°C inside and 0°C outside, the roof loses about 552 W through 16 mm polycarbonate and about 103 W through panels.
Because the inner skin stays close to room temperature, condensation largely stops. The opaque roof blocks direct summer sun on the roof, and the foam core damps rain noise. If you are worried about light, glazed roof lights can be set into the panel roof, and most people choose one or two. Our page on replacing a polycarbonate conservatory roof shows how the swap works.
Honest trade-offs
An insulated roof costs more than new polycarbonate. Small roofs start from £3,000 and most homes pay £3,000 to £7,500, against £2,000 to £3,500 for new sheets on a small roof. The room will also be darker than under a clear roof, which roof lights and LED spotlights help with but do not fully replace.
A simple test: put a cheap thermometer in the conservatory and one in the next room on a cold evening. A gap of more than 8 to 10°C with the heating on means the roof is losing heat faster than you can put it in.
When to act
If you see one sign, keep an eye on it and fix it cheaply. If you see three or more, especially discoloured sheets with leaks and condensation, the roof is near the end of its useful life. Lead time is typically 3 to 5 weeks from survey, so it pays to book before the colder months rather than after the first bad storm.
Next steps
Get a price range in a minute with the conservatory roof cost calculator, then book a free survey. We will look at the roof, the frame and the gutters, and tell you honestly whether a repair would do for now.
Questions people ask
How long does a polycarbonate conservatory roof last?
Usually about 10 to 20 years. South facing roofs tend to yellow and turn brittle sooner because they get the most sun.
Can I replace just a few polycarbonate sheets?
Yes, single sheets can be swapped. On an older roof the new sheets will look clearer than the rest, and the seals on the other sheets are often of the same age.
Is heavy condensation a sign the roof is failing?
Not always failing, but it shows the roof is cold on the inside and losing a lot of heat. An insulated panel roof keeps the inner surface close to room temperature, so condensation largely stops.
What is the best time of year to replace a conservatory roof?
Any dry spell works, and we fit all year. Booking in late summer means the new roof is on before the heating season, with a typical lead time of 3 to 5 weeks.
