5m x 4m Conservatory Cost UK 2026: £18,000 to £30,000
uPVC from £18,000, hardwood from £32,000, orangery from £35,000. Twenty square metres, eight to fourteen days on site, the size at which warm roof becomes essential.
Updated May 2026. FMB, Checkatrade, Which?, and Homebuilding and Renovating data.
5m x 4m Prices by Style (2026)
| Style | uPVC | Aluminium | Hardwood |
|---|---|---|---|
| Lean-to (5m x 4m) | £18,000 - £23,000 | £23,000 - £30,000 | £32,000 - £40,000 |
| Edwardian | £20,000 - £26,000 | £26,000 - £34,000 | £35,000 - £45,000 |
| Victorian (5-facet) | £23,000 - £30,000 | £30,000 - £39,000 | £40,000 - £52,000 |
| Gable-end | £24,000 - £31,000 | £31,000 - £40,000 | £42,000 - £55,000 |
| P-shaped (5x4 + 2x3 wing) | £26,000 - £35,000 | £35,000 - £45,000 | £46,000 - £58,000 |
| Orangery | £35,000 - £45,000 | £40,000 - £52,000 | £52,000 - £68,000 |
Includes supply, install, base, glass roof, basic electrics. Excludes flooring, warm roof upgrade, knock-through structural work, VAT. Source: FMB 2026, Checkatrade.
The Family Room Sweet Spot
Twenty square metres in a 5 by 4 metre footprint is the threshold at which a conservatory becomes a proper family room rather than a glazed addition. The geometry is generous enough for genuine multi-function use: a 6 to 8 seater dining table, a 3-seater sofa with two armchairs around a coffee table, a children's play corner, and clear circulation between all three zones. A typical UK family of four can use a 5x4 daily for meals, evening relaxation, homework, and weekend entertaining without anyone feeling cramped.
The 4 metre projection into the garden also makes the conservatory feel architecturally substantial. Viewed from the garden, a 5x4 reads as a proper rear extension rather than a tacked-on glasshouse. Combined with brick or stone dwarf walls (£600 to £1,500 extra over standard PVC dwarf walls) and a gable-end or hipped Edwardian roof, the result is a meaningful design statement. This is the size at which estate agents start describing the result as adding habitable space rather than a conservatory in particulars.
The flip side: at 20 m², the heat loss in winter and solar gain in summer are no longer trivial. A glass-roofed 5x4 with double glazing loses roughly 1 to 1.4 kW on a typical UK winter night even with the door to the house closed. Heating that load via a single electric radiator is unrealistic. The room becomes seasonal unless a warm roof, underfloor heating, or both are specified from day one. This is why the cost gap between a base spec 5x4 and a properly habitable 5x4 is roughly £10,000 to £15,000.
Prior Approval Notification: Step-by-Step
For an attached house, a 5x4 with the 4 metre dimension projecting into the garden requires the larger home extension prior approval. This is not full planning permission but a structured notification process. Step one: prepare a site plan and elevation drawings showing the proposed extension dimensions, materials, and finish. Most installers provide this as part of their quote (no additional cost) but if you are managing the project yourself, a CAD drawing from a freelance technician is roughly £200 to £400.
Step two: submit the notification to the local authority via the Planning Portal. Fee is approximately £96 in England (2026 rate; check current). The portal accepts payment online and routes the application to your council automatically. Step three: the council notifies your adjoining neighbours (those sharing a boundary). Neighbours have 21 days to object. If no objections come in, the council issues prior approval and you can build.
Step four: if a neighbour objects, the council has a further 21 days to assess the impact on neighbouring amenity. The test is narrower than full planning: only the impact on neighbour daylight, outlook, and privacy is considered, not broader planning matters such as design or general appearance. Most objections are overruled provided the proposal meets the technical standards. If approval is refused, you can either redesign and resubmit (no extra fee within a 12 month window for the same site) or appeal via the Planning Inspectorate, which takes 8 to 20 weeks. In practice, 92% of prior approval applications go through on the first submission (Department for Levelling Up data, 2024).
Warm Roof at 5x4: The Single Most Valuable Upgrade
A 5x4 conservatory has 20 m² of roof area. With standard 28 mm sealed double-glazed glass roof units (U-value 1.5 to 1.7 W/m²K), the roof alone loses 30 to 34 watts per m² per degree of temperature difference. On a cold UK winter night with the room at 12 degrees and the outside at -2 degrees, that is 840 to 950 watts of heat loss through the roof alone, before considering the walls.
A warm tiled roof (Equinox, Guardian Warm Roof, or similar) replaces the glass with insulated tiles over a structural deck. U-values drop to 0.15 to 0.18 W/m²K, around an order of magnitude better. The same 20 m² loses 60 to 75 watts in the same conditions. The internal temperature rises by 6 to 9 degrees compared to a glass roof with the same heating input, and crucially the summer solar gain drops by 80%, eliminating the conservatory greenhouse effect.
First-install warm roof on a 5x4 in 2026: typically £6,500 to £11,000 over the glass roof baseline. Retrofit cost three years later: £8,500 to £14,500 because the existing structural deck usually needs reinforcement to take the additional roof load. The retrofit premium is therefore £2,000 to £3,500. Combined with the room being habitable from day one rather than two summers in, the first-install warm roof is one of the rare upgrades that genuinely pays for itself in usability terms.
5m x 4m Conservatory Cost Calculator
Enter 5 in width and 4 in depth for a 5x4 estimate. Toggle between glass roof and warm roof to see the cost impact.
Conservatory Cost Calculator
Enter your details for a 2026 price estimate. Based on FMB, Checkatrade, and Which? data.
Floor area: 12.0 m2
Estimated Total Cost
£14,800 to £30,300
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Cost Breakdown
Excludes: flooring, heating, furniture, VAT where applicable, planning fees. VAT is typically 20% on labour and materials.
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5m x 4m Conservatory FAQ
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Related Pages
4m x 4m (16 m²)
Down a size. Square footprint, open-plan kitchen-diner sweet spot. £16,000 to £28,000.
6m x 4m (24 m²)
Up a size. Likely needs full planning. £22,000 to £40,000.
Warm Roof Conversion
Full retrofit costs and structural considerations for converting a 5x4 glass roof.
Orangery at 5x4
The premium spec: brick pillars, solid insulated roof, central glazed lantern.
Planning Permission
Larger home extension prior approval explained step by step.
Heating
Why a 5x4 with a glass roof is rarely usable year-round without a warm roof or underfloor heating.