Replace a polycarbonate conservatory roof with a solid insulated one

Is your polycarbonate finished?

Tick off what you see:

• The sheets have gone yellow, grey or green, and cleaning does not bring them back.
• Black lines run down inside the channels where dirt and algae have got in.
• Rain on the roof is loud enough to stop a conversation or drown the television.
• Water drips from the ceiling on cold mornings, even when it is not raining.
• One or more sheets have crept down the slope and sit proud of the gutter.
• The room needs a heater on from October to April and a fan from June to August.

Two or three ticks is normal for a roof over 15 years old. It does not mean the conservatory is finished. It means the roof is.

What solid means here

"Solid roof" gets used for two different jobs, so it is worth being clear. We do not build a new roof frame or add a plastered ceiling. We take out the polycarbonate sheets and fit made to measure insulated panels into your existing roof frame. Each panel is two aluminium skins with a 75 mm solid foam core, coloured outside and white inside.

That is why the job takes days rather than weeks, and why the price starts at £3,000 rather than several times that. The price page sets panels against the other ways to go solid.

Your thickness, in numbers

Polycarbonate comes in three common thicknesses. Look at the edge of a sheet at the gutter end to see which you have. The table compares each with our panel for a 12 m² roof, on a cold evening with 20 degrees between the room and outside, and across a typical English heating season of about 2,150 degree days.

Savings assume electric heating at 26.32p a unit, the Ofgem cap rate for the last quarter of 2026. Heating with gas at 7.97p through a 90% boiler? Divide by about three. Whatever the thickness, the panel cuts roof heat loss by at least 69%, and by about 81% against 16 mm.

New polycarbonate or panels: an honest comparison

You could have the sheets replaced like for like. Published UK cost guides put a 3 m by 3 m polycarbonate roof at roughly £2,000 to £3,500 fitted, so it can be the lower price on the day. But you get the same U-value back, the same noise, and the same slow fade to yellow over the next decade or so.

If you mainly want light and use the room a few months a year, new polycarbonate is a fair choice. For a room you mean to sit in through January, panels are the better spend. Our guide to the cheapest way to replace a conservatory roof runs through every option.

The swap, step by step

1. Survey: we measure every bay, check the bars, the wall plate, the gutter and the base, and give you a fixed written price.
2. Building control: the spec is talked through with the council, and the application goes in under our name.
3. Making: your panels are made to size, which takes 3 to 5 weeks.
4. Stripping: the bar caps come off and the polycarbonate sheets are lifted out. They are light, so this part is quick.
5. Checking: with the roof open, we look at every bar and seal before anything goes back.
6. Fitting: panels go in bay by bay, sealed along each bar, then capped.
7. Finishing: new flashing at the house wall, trims, gutters cleared.
8. Clearing: old sheets and caps go on our van for recycling.

Plan on 1 day for a small roof, 1 to 2 for a medium one and 2 to 3 for a large one. Most single storey conservatories need no scaffold.

A worked example

A 3 m by 3.6 m Edwardian with 25 mm sheets, about 12 m² of roof, heated by a 2 kW oil filled radiator. On a cold evening the roof loses about 384 watts, so a fifth of the heater's output goes straight up. With panels it loses about 103 watts. Across the year, about 724 kWh less, which is roughly £191 on that electric radiator.

The price for that roof would be about £3,500 to £4,100 fitted, before any roof lights. The price page covers every size.

Keeping some light

Going from clear sheets to a solid roof is a big change in light. Most people add at least one glazed roof light at £395, placed near the house wall where the room is darkest. See roof lights and spotlights.

Building control and planning

Clear polycarbonate keeps your conservatory exempt from building regulations. Panels end that, because the exemption only holds while three quarters or more of the roof lets light through. Expect building control to be involved. Approved Document L 2021 sets 0.15 for a new roof element, and a 0.43 panel will not hit that by itself. That is exactly why the spec gets agreed with your council before anything is made. Planning, by contrast, rarely comes into it, because nothing grows. Only listed homes, national parks, conservation areas, National Landscapes and properties stripped of permitted development rights need a closer look. Every roof shape is on the insulated conservatory roof page.