Installed uPVC prices, size by size, from sourced 2026 guides: a 3m x 3m lean-to from £5,000, mid-size builds £7,000 to £17,500 depending on style, and orangeries £20,000 to £50,000 and up. Every figure below carries its source and date, the differences between the guides included; no installer behind this page and no lead selling.
| Size | Lean-to (uPVC) | Victorian | Edwardian |
|---|---|---|---|
| 3m x 3m (9 m²) | £5,000 to £9,000 | £8,000 to £12,500 | £8,500 to £13,500 |
| 3m x 4m / 4m x 3m (12 m²) | £6,000 to £10,500 | £9,000 to £14,000 | £9,500 to £15,000 |
| 5m x 3m (15 m²) | £7,000 to £12,000 | £10,000 to £16,000 | £10,500 to £17,000 |
| 4m x 4m (16 m²) | £7,500 to £12,500 | £10,500 to £16,500 | £11,000 to £17,500 |
| 5m x 4m (20 m²) | £8,500 to £14,500 | £12,000 to £19,000 | £12,500 to £20,000 |
| 6m x 4m (24 m²) | £10,000 to £17,000 | £14,000 to £22,500 | £15,000 to £24,000 |
Installed, including frames, glazing, a standard base and VAT (BestBuilders, August 2026, regional cost model with quarterly review). The second benchmark sits higher: RenovationCosts' trade data puts a typical full project at £18,360 to £24,840, largely because real jobs add groundworks (£1,800 to £4,800) and extras on top. Read both as the honest spread, not as a contradiction to pick a side in.
Planning follows the same permitted development rules as any extension; the free planning permission check walks your situation question by question. The building regulations exemption is the quiet reason a conservatory prices below an extension, and it has exact conditions (Planning Portal): ground level and single storey, under 30 square metres, separated from the house by external quality walls, doors or windows, an independent heating system with its own controls, and compliant glazing and electrics. Remove the dividing doors or break a condition, and the room legally becomes an extension.
A mid-range single-storey rear extension runs £48,000 to £72,000 in our validated price data, the same source as the calculator. The conservatory buys light and floor space for less; the extension buys an unrestricted, fully insulated room. The full comparison lives in the extension guide and extend or move; and when quotes arrive, the quote check reads them line by line, because both sources measure spreads of tens of percents between firms for identical specs.
Sources, all opened 30 August 2026: BestBuilders, Conservatory Cost by Size & Type (updated 21 August 2026, regional cost model, quarterly review); RenovationCosts.co.uk, Conservatory Cost UK (trade benchmark data, updated 2 May 2026); Planning Portal, Conservatories: building regulations and planning permission. The extension comparison comes from our validated 2026 UK price data.
£5,000 to £9,000 installed as a uPVC lean-to, £8,000 to £12,500 in Victorian style and £8,500 to £13,500 in Edwardian style, including frames, glazing, a standard base and VAT (BestBuilders, August 2026). The bottom of each range is a polycarbonate roof, the top an A-rated glass roof. Note the second benchmark: RenovationCosts' trade data puts a typical full project at £18,360 to £24,840, because real jobs often add groundworks (£1,800 to £4,800) and extras on top of the base tables.
Substantially, and here both sides come from checkable data: the conservatory tables above run £5,000 to £24,000, while a mid-range single-storey rear extension is £48,000 to £72,000 in our validated price data. The gap has a legal reason: a conservatory under 30 square metres that stays separated from the house is exempt from most building regulations. The moment you remove the dividing doors or fit a heavy solid roof, it is treated as an extension, with the regulations and the price tag that belong to one.
Usually not: a conservatory follows exactly the same permitted development rules as any extension (Planning Portal). Single storey, behind the principal elevation, height and projection within the limits, and no more than half the garden covered. Listed buildings and conservation areas are stricter. Check your own situation in minutes with the free planning permission check, question by question.
On a new build a solid tiled roof adds £4,000 to £8,000 over polycarbonate; retrofitting one on an existing conservatory runs £4,000 to £12,000 depending on size and whether the frames need strengthening. Two honest warnings from the sources: a solid roof needs building regulations sign-off (the exemption assumes a translucent roof and independent heating), and a surveyor should confirm the frames and base can carry the weight before you commit.
Both sources say it plainly: quotes for identical specs routinely vary 20 to 30 percent between firms (BestBuilders), and RenovationCosts measures spreads of 40 to 80 percent on full projects, with foundations varying five-fold with ground conditions. The defence is boring and effective: three like-for-like quotes with the frame system, roof type and base itemised, and a check of the winning quote line by line before signing.