What an orangery is vs a conservatory or extension
Orangery: hybrid between a conservatory and a brick extension. Solid masonry or oak base walls (1.2–1.8m high), structural columns or piers, glazed roof with a flat perimeter and a central lantern, full-height French or bifold doors. Typically has its own heating and underfloor heating, suitable for year-round use. Conservatory: lightweight uPVC or aluminium frame with full-height glazing on three sides and a polycarbonate or glass roof. Not heated and not part of the thermal envelope. Extension: full brick or timber-framed addition with conventional roof, treated as part of the house thermal envelope. Orangery sits between — premium feel and architectural presence, year-round use, but glazed-roof character that distinguishes it from a standard rear extension.
Cost breakdown
Oak frame (supply only, 15–25m²): £18,000–£45,000 — Wealden, Border Oak, English Heritage Oak, Welsh Oak Frame. Roof lantern (glazed): £8,000–£18,000 — Atlas, Korniche, Solarlux Roof. Base wall (brick or rendered cavity wall, 1.2–1.8m high): £8,000–£18,000. French or bifold doors (full-height): £6,000–£15,000 — aluminium Schueco or Reynaers. Foundation (typically trench fill with insulated screed): £6,000–£12,000. Underfloor heating: £3,000–£6,000. Electrics, lighting, finishes: £6,000–£12,000. Total turnkey 20m² orangery: £75,000–£120,000 standard spec; £120,000–£165,000 high-end with bespoke joinery, premium glazing and architectural lighting.
Planning and Building Regulations for orangeries
Planning: orangeries qualify as householder extensions under the same rules as any rear extension — most are permitted development under Class A (single-storey, no further than 6m from rear wall on terraced, 8m on detached). Conservation areas require full planning. Building Regulations: orangery is treated as a thermal element when it has 75%+ glazed roof and qualifies for the 'conservatory exemption' (Approved Document L1B). Most modern orangeries do NOT meet this exemption — too much insulation, fixed thermal partition, year-round heating. Typically the orangery is designed as a habitable extension fully compliant with Part L, U=0.18 walls, U=0.13 roof flat perimeter, U=1.6 glazed lantern.
