Quick answer: A conservatory (mostly glass, 50%+ glazed roof) costs £8,000–£25,000 in 2026. An orangery (more brick walls, partly glazed roof) costs £20,000–£60,000. A full extension (solid roof, only walls and windows glazed) costs £40,000–£120,000+. The three look similar in marketing photos but they’re three regulatory categories with very different planning rules, Building Regs requirements, and resale-value impacts. This guide explains which is which, what each actually costs in 2026, when each makes sense, and the planning-permission shortcuts that can save thousands.
The 3 categories — official definitions
The legal distinction matters because conservatories and orangeries can be exempt from Building Regs Part L (energy efficiency) under specific conditions; extensions never are. The exemption can save £3,000–£8,000 in compliance costs — but only if you actually meet the criteria.
| Conservatory | Orangery | Extension | |
|---|---|---|---|
| Roof glazing | ≥75% glazed | ≤25% glazed (~50% in marketing terms but legal definition stricter) | Solid roof; rooflights optional |
| Walls | ≥50% glazed | Mostly brick/render; window openings 25–50% of wall area | Solid walls with normal window openings |
| Connection to house | External-quality door separates from house | External-quality door (sometimes — see below) | Open to house; integrated heating |
| Heating | Independent of house heating | Independent (if exempt) | Connected to house heating |
| Building Regs Part L | Exempt if <30m² + thermally separated | Sometimes exempt — depends on spec | Always applies |
| Typical cost | £8,000–£25,000 | £20,000–£60,000 | £40,000–£120,000+ |
The “is it an orangery or an extension?” line is where most disputes happen. The Building Regs test isn’t about brand marketing — it’s about whether the structure is thermally separated from the house. If a contractor wants to call something an orangery to avoid Part L compliance, the test is: can you close it off from the rest of the house with an external-grade door, and is its heating independent? If yes, exempt. If no, it’s an extension.
Conservatory — cost breakdown
- Lean-to (3m × 3m), uPVC, polycarbonate roof: £6,000–£10,000
- Lean-to (3m × 3m), uPVC, glass roof: £8,000–£14,000
- Victorian (3.5m × 3.5m), uPVC, glass roof: £12,000–£18,000
- Edwardian (4m × 4m), uPVC, glass roof: £14,000–£22,000
- P-shape or T-shape (5m × 4m), uPVC, glass roof: £18,000–£28,000
- Aluminium framing (any of the above): +30–50%
- Solid roof upgrade (now extension by Building Regs definition): +£3,000–£8,000
- Bi-fold doors instead of standard French: +£2,500–£5,500 (see bi-fold doors guide)
- Underfloor heating: +£1,500–£3,500
The polycarbonate roof option still exists at the budget end — performance is much worse than glass (overheats in summer, cold in winter, drumming noise in heavy rain) but it’s £3,000–£5,000 cheaper. Most homeowners now upgrade to glass roof from the start; if you’re stuck with polycarbonate from a previous install, see our conservatory roof replacement guide.
Orangery — cost breakdown
- Small orangery (3m × 3m), uPVC framework + brick base wall: £20,000–£28,000
- Standard orangery (4m × 3m), uPVC framework + brick: £25,000–£35,000
- Larger orangery (5m × 4m), aluminium framework + brick: £35,000–£50,000
- Premium orangery (6m × 4m+), bespoke aluminium + lantern roof: £45,000–£70,000+
Orangeries cost roughly 2× a comparable conservatory because of the brickwork, the lantern roof structure, and the fact that they’re usually built with kitchen-extension-style spec (proper foundations, real heating, often plumbing for a kitchen extension). Adds significant resale value — typically 5–10% of property value vs ~2–4% for conservatory.
Full extension — cost breakdown
- Single-storey rear extension (3m × 3m), basic spec: £30,000–£45,000
- Single-storey rear extension (4m × 4m), mid spec: £45,000–£70,000
- Single-storey side return (3m × 5m), London/SE prices: £55,000–£90,000
- Wraparound (5m × 6m, kitchen/diner): £80,000–£140,000+
- Two-storey extension: roughly 1.5× single-storey for the additional floor
Extension prices vary hugely by region (London/SE often 2× northern prices for same spec) and by spec choices (basic vs premium kitchen, underfloor heating, glazing area, finishes). The “London uplift” alone can add 50–80%.
Planning permission — the permitted development shortcut
Most rear conservatories, orangeries and single-storey extensions fall under Permitted Development Rights in England (similar but not identical rules in Scotland, Wales, NI). Key 2026 rules for single-storey rear additions:
- Detached house: up to 8m projection rear (was 4m pre-2019 changes), max 4m height at eaves
- Semi-detached or terrace: up to 6m projection rear (was 3m), max 4m height at eaves
- Side returns: up to half the width of the original house
- Coverage: maximum 50% of original garden / curtilage as built
- Materials: must “match or be similar to” the existing house
- “Larger Home Extension” notice required to your council if you go beyond 4m / 3m (free; ~6 weeks; neighbours can object)
Excludes: conservation areas (always need full planning), listed buildings (always need listed building consent + planning), Article 4 directions (locally varies), flats (no PD for flats — always need planning).
Always check with your local planning office before paying for designs. A free 5-minute “duty officer” call confirms PD eligibility for most homes.
When to choose each
Conservatory makes sense if…
- Budget is constrained (£8,000–£20,000 max)
- Use it as a “garden room” — extra living space when weather permits, not your main living room
- You’re happy to keep the house’s existing kitchen / dining configuration
- Resale value uplift is secondary to immediate enjoyment
Orangery makes sense if…
- Budget allows £25,000–£50,000
- You want all-year-round living space, not just summer
- You want the architectural look of “added room” rather than “added structure”
- You’re willing to accept the legal / Building Regs ambiguity around exemption
- Resale value matters — orangeries add more per £ spent than conservatories
Full extension makes sense if…
- Budget is £40,000+
- You want truly integrated living space (kitchen / diner / family room)
- Building Regs compliance is fine — you’re moving heating system, plumbing, etc. anyway
- You’re staying long-term and want the resale value
- You need bedroom / bathroom additions (not legal in conservatory definition)
What to ask any installer
- “Is this legally a conservatory, orangery, or extension under Building Regs?” Get the answer in writing. Affects everything else.
- “Is it Building Regs exempt or notifiable?” If exempt, what’s the legal basis? If notifiable, who’s filing the notice (FENSA/CertAss self-cert or local authority Building Notice)?
- “What’s the U-value of the roof and the walls?” Should be ≤1.6 W/m²K for roof, ≤1.4 for windows. See our U-values & WER guide.
- “Will the install need planning permission, prior approval, or neither?” Get a written confirmation; never assume “we know it’s PD.”
- “Are foundations strip or trench-fill, and what depth?” Conservatories sometimes get away with lighter foundations; orangeries and extensions need full structural foundations.
- “What’s the lead time, payment schedule, and FENSA notification timeline?”
- “Is the install covered by an insurance-backed guarantee?” See our IBG decoded guide.
Common mistakes
- “It’s an orangery so we don’t need Building Regs.” Only if the structure is genuinely thermally separated from the house. If you take internal walls down to integrate it, you’ve created an extension and Building Regs apply retrospectively.
- Removing the original external door connecting house to conservatory. This breaks the thermal-separation requirement — house’s heating becomes responsible for conservatory, and the EPC fails.
- Underestimating heat / cooling. Glass-heavy structures need either solar control glass (south-facing), proper ventilation, or both. Otherwise unusable June–August.
- Choosing polycarbonate roof to save money. The roof is the most-replaced part of any conservatory; spending the extra £3,000 upfront for glass saves £6,000+ in 10 years.
- Picking the cheapest installer with no IBG. Same risk as windows — cover disappears if the company folds.
Frequently asked questions
How much value does each add to my house?
Industry estimates (which vary widely by region and condition): conservatory adds ~5% of property value; orangery adds ~7–10%; full extension adds ~10–15% (and sometimes more if it adds bedrooms). The ROI doesn’t always exceed the spend — especially for conservatories where build cost can equal or exceed the value uplift.
Can I convert my old conservatory into an orangery or extension?
Yes. Replacing the polycarbonate roof with a solid (warm) roof, adding more brickwork, and integrating it with the house’s heating turns a conservatory into a habitable extension — but triggers full Building Regs compliance retrospectively. Budget £8,000–£25,000 for a meaningful upgrade.
Do I need an architect?
For a standard conservatory or orangery with the installer’s stock designs: usually no. For anything bespoke, large, or full extension: yes — architect fees are 5–12% of build cost and well worth it for design quality and Building Regs efficiency.
What about heating an orangery?
If exempt: independent heating only — typically electric panel heaters or a separate combi for that room. Connecting to the house’s central heating turns it into an extension under Building Regs (which you may or may not want). Underfloor heating is popular and works well in either category.
Do conservatories really overheat as much as people say?
South-facing ones with no solar control glass and no ventilation: yes, summer temperatures can reach 40°C+. North-facing or east-facing with proper glass spec and an opening roof vent: comfortable year-round. Solar-control glass + opening vent + ceiling fan = transformative for usability.
Can I finance an orangery or extension?
Yes — most installers offer finance up to ~£25,000. Beyond that, secured home-improvement loans or remortgaging are standard. See our finance guide for current UK options.
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Related: Conservatory Roof Replacement · Roof Lanterns vs Skylights · Bi-Fold Doors Cost
Sources: Approved Document L (2022), Approved Document Part 7 (Conservatory exemption clauses), Permitted Development Rights guide (gov.uk planning portal), Anglian Home Improvements published price ranges 2026, Everest orangery pricing data, Farrow Jones orangery vs conservatory comparison, Checkatrade extension cost guide (2026), HomeOwners Alliance ROI guidance. Last reviewed: April 2026.
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