Swapping Polycarbonate for Glass or a Solid Roof
Three jobs get quoted under one heading and they are not the same job. Like for like restores the roof. Glass keeps the light and improves the numbers a little. Going opaque changes the room and turns the work into replacing the whole roof. What each word means is on conservatory roof coverings.
Polycarbonate, like for like · existing 3m × 3m conservatory · installed, inc VAT
£1,900 to £3,500 glass costs £500 to £1,000 more
Reasonably evidenced2 sources · floor agrees within 1.32× · a UK price guide 27 July 2026 and Homebuilding 18 April 2024 · checked 20 August 2026
What does it cost to replace a polycarbonate conservatory roof?
Like for like on a 3m by 3m conservatory costs £1,900 to £3,500 installed including VAT. Two independent publishers price it and their floors sit within 1.32×, which is good agreement for this niche given one is a lead-generation marketplace and the other is neutral editorial. Upgrading the same roof to glass costs £500 to £1,000 more. Checked 20 August 2026.
Two supporting rows: a Victorian 4m by 4m polycarbonate roof runs £3,500 to £4,800 (Homebuilding, 18 April 2024, Thin evidence), and the installed rate is £175 to £350 per square metre (a UK price guide, 27 July 2026, Thin evidence). Both checked 20 August 2026.
The figure you will have seen elsewhere, and why we do not use it
One large national directory publishes a polycarbonate band of £6,300 to £12,150 (March 2026), roughly 2.5× above both publishers above. It is one of the most widely repeated figures in the niche because other sites quote it. Our reading, stated as a reading rather than a fact, is that it carries whole-conservatory figures under a roof label. We exclude it from our polycarbonate rows and publish it here, named, rather than dropping it quietly, because you have probably already seen it.
use the Conservatory Cost Calculator to put your own size band against these rows.
Your three options, priced
Everything quoted for a tired polycarbonate roof is one of these three. They differ by about 6× from end to end, and they differ far more than that in what they do to the room.
| Option | Low | Typical | High | Evidence | What it changes |
|---|---|---|---|---|---|
| Like for like polycarbonate | £1,900 | not published | £3,500 | Reasonably | Watertight and clean again. Temperature unchanged |
| Upgrade to glass | £2,000 | £4,000 | £7,000 | Reasonably | Quieter in rain, better glazing U-value, same daylight |
| Go solid or tiled | £6,000 | £8,075 | £11,000 | Well | Usable all year. Costs you daylight, becomes regulated work |
Polycarbonate: a UK price guide 27 July 2026 and Homebuilding 18 April 2024. Glass: four publishers, and the typical of £4,000 is one of their own point estimates rather than a midpoint. Solid or tiled: four publishers, and the typical of £8,075 is the median of five sourced point estimates. At 4m by 4m the glass band is £4,000 to £7,500, typically £5,850, across three publishers. Checked 20 August 2026.
The cleanest published number on this page is the one that compares two of those rows directly: like for like, glass costs £500 to £1,000 more than polycarbonate (one UK cost publisher, 15 August 2024, Thin evidence). Nobody else in the niche states the premium as a number at all. Treat it as the shape of the decision rather than as a quotation, and price glass as a total using the row above. The full glass specification, coatings included, sits on replacing a conservatory roof with glass, and the solid route is priced at how much a solid conservatory roof costs.
Why polycarbonate fails
Multiwall polycarbonate is a plastic sheet with hollow flutes running through it. It is light, cheap and easy to cut, and none of that helps it on a south-facing roof after twenty years. Four things go wrong, in much the same order on almost every conservatory.
- Summer heat. A thin translucent skin lets solar gain straight in. Tinting helps: at 25mm, solar transmission runs from 63 per cent for clear down to 8 per cent for a heat-reflective grade, on Ultraframe's published figures. Most conservatories were glazed clear or opal.
- Winter heat loss. The roof is the worst-performing surface on the house, and the section below puts a number on it.
- Rain noise. A drumming skin over a hard room. Nothing fixes it except mass, which is why glass is quieter and a solid roof is quieter still.
- Discolouration and algae. Once the sealing tapes at the sheet ends degrade, moisture and dirt get into the flutes and green streaks appear inside the sheet where no cleaning can reach.
None of that is a defect. It is what the material does over time, and it is the reason the three options above exist rather than a repair.
How long does polycarbonate last? We do not have a sourced figure
No publisher in our register gives a lifespan for a polycarbonate conservatory roof, and we will not invent one, because that number would be doing real work in your decision. What would close it: a manufacturer's published service-life statement, or a warranty term in years on a UK distributor's technical sheet. Until then, judge yours on the four failure modes above rather than on its age. how long a conservatory lasts covers the frames and the base as well as the roof.
Polycarbonate U-values go by wall count, not thickness
This is the single most repeated error in the niche. A sheet's U-value depends on how many internal walls the extrusion has, not on how thick it is. Two 16mm sheets differ by 0.6 W/m²K, from 2.4 for triplewall down to 1.78 for sevenwall. If a quote gives you a single U-value against a thickness alone, it has not been checked.
| Sheet | U-value, W/m²K | What the spread is |
|---|---|---|
| 10mm | 2.2 to 3.2 | Twinwall 3.2, fourwall 2.5, sixwall 2.4 |
| 16mm | 1.78 to 2.4 | Triplewall 2.4, X-wall 2.0, fivewall 1.9, sevenwall 1.78 |
| 25mm | 1.4 to 1.7 | Fivewall 1.6, 7X-wall 1.4, Ultraframe standard 1.7 |
| 35mm | 1.08 to 1.5 | Sevenwall 1.2, tenwall 1.08, Ultraframe standard 1.3 |
| 55mm | 0.83 | Tenwall. The best figure available on the UK market |
Brett Martin Marlon ST brochure p.29, with Palram, Arla Plast and the Ultraframe polycarbonate leaflet v5 of October 2023. Verified 20 August 2026.
Now the comparison that decides most of these jobs. A replacement roof in an existing dwelling has to reach 0.15 W/m²K under Approved Document L Table 4.2. Even the best polycarbonate on the market, a 55mm tenwall sheet at 0.83, is more than five times that limiting value. A conservatory glazed in 25mm is roughly ten times it. That is the whole argument for a solid roof, and it is also why a like-for-like polycarbonate replacement stays outside the building control regime while a solid one does not.
Removal, disposal, and what is in the price
Taking the old polycarbonate roof off and getting rid of it runs £200 to £400 (a UK price guide, 2026, one publisher, Thin evidence, checked 20 August 2026). On a like-for-like job it is usually inside the quoted price. On an upgrade, ask about it explicitly: the old roof is scrapped, not credited.
One honesty line about what you are actually buying. Polycarbonate sheet as a material costs £35 to £50 per square metre supply only (one publisher, undated, Thin evidence). Installed, the same roof is £175 to £350 per square metre. The material is roughly one sixth of the job. The other five sixths are access, removal, glazing bars, sealing, labour and VAT, which is why a supply-only price you find online is not a comparison against an installer's quote.
Normally included
- Removal and disposal of the old sheets
- New multiwall sheet, cut to the existing bars
- New end tapes and sealing
- Replacement glazing bar caps where needed
- VAT at 20 per cent
Normally not
- Scaffolding, if the roof cannot be reached safely
- A new glazing bar system rather than reglazing the old one
- Guttering and downpipes
- Any repair to the ridge, box gutter or wall abutment
- Making good to the frames
Inclusions are the common scope across the two publishers pricing this job; where a line is not stated by either, we have marked it as normally excluded rather than assuming it in. Checked 20 August 2026. If yours is leaking rather than tired, a repair may be the better buy, and that is set out at leaking conservatory roof repairs.
Price your job in six questions
The first question is what your roof is made of now, because that is what decides which of the three jobs above you are actually buying.
What would yours cost?
Six questions, about sixty seconds.
Rather skip the questions? You can get roof replacement quotes directly, or find conservatory roofers near you.
If the sheets are coming off anyway, should you do the whole roof?
The price gap makes this unavoidable. A like-for-like job is £1,900 to £3,500 at 3m by 3m, Reasonably evidenced from two publishers. A solid or tiled roof on the same conservatory is £6,000 to £11,000, typically £8,075, Well evidenced across four publishers whose floors agree within 5 per cent. Both checked 20 August 2026. The upgrade is roughly three times the money, and it is the only one of the three that makes the room usable in January and July.
What tips it, in our reading, is scaffolding and access. Both jobs need the roof opened up and both need the old covering taken away, so a chunk of the cost of the cheap job is spent again if you upgrade in three years. Set against that: a solid roof takes daylight out of the room, adds weight your existing mullions may or may not be reinforced for, and turns an exempt conservatory into notifiable building work at 0.15 W/m²K.
None of that is a reason to be talked into the bigger job on the doorstep. It is a reason to price both before you decide. The full money table, size band by size band, with the per square metre reconciliation and the itemised exclusions, is on replacing the whole roof.
If you do go solid, the sign-off route is the part installers are vaguest about. It goes to Local Authority Building Control or a Registered Building Control Approver, and no competent person scheme covers it: FENSA says in its own words that conservatories fall outside its scheme, and CERTASS lists conservatories under what cannot be registered. That is set out at the building control route for a roof replacement.
Or just clean it
Worth ruling out before you spend anything. If the sheets are sound and the complaint is that the roof looks green and tired, cleaning the outer surface and the glazing bars costs a fraction of any of the three options above. What it cannot fix is algae inside the flutes, which arrives once the end tapes have gone and which no cleaning reaches. Method and cost are at how to clean a conservatory roof.
Questions people ask first
How much does it cost to replace a polycarbonate conservatory roof?
Is it worth replacing polycarbonate with glass?
Can I replace polycarbonate with glass in the existing bars?
Do I need building regulations approval to replace it like for like?
What thickness of polycarbonate should I ask for?
Why is the polycarbonate price online so much lower than my quote?
Every figure on this page was last checked 20 August 2026, next check due 20 November 2026. Where one publisher prices a row alone we grade it Thin and say so; where a widely repeated figure sits outside the rest of the market we name it and give the reason rather than dropping it. See what a conservatory costs for the same method across the whole job.
Find out what yours costs
Six questions, about sixty seconds, and an estimate built from published UK figures with every source shown. Then up to four local installers can quote you, if you want them to.