Conservatories vs Orangeries in London: Costs, Planning, and Differences

The legal distinction between a conservatory and an orangery matters because it affects whether Building Regulations apply: Conservatory: a glass or substantially glazed structure where at least 50% of the roof is translucent (glass or polycarbonate), at least 50% of the walls are glazed, and the structure is thermally separated from the main house by external-quality walls, doors, or windows (i.e., the rest of the house can be shut off from the conservatory). A conservatory meeting these criteria is exempt from the energy efficiency requirements of Building Regulations (Part L) — provided it does not exceed 30m² in ground area. Orangery: an extension with a solid lantern roof (typically with a perimeter glazed section at the top) and solid masonry or rendered walls. The glazed area of the roof and walls may still be substantial, but the roof structure is predominantly solid rather than wholly glazed. An orangery does NOT meet the conservatory exemption criteria and IS subject to the full Building Regulations requirements, including Part L energy efficiency. Glass extensions / frameless glass extensions: a modern variant of the orangery concept using structural glass and glazed roofs — also fully subject to Building Regulations. In practice, most modern glass additions to London homes are technically orangeries or glass extensions (not true conservatories) because they feature solid elements to the roof structure and do not have the thermal separation from the house that a true conservatory requires. A true polycarbonate-roofed conservatory that is thermally separated and under 30m² is increasingly unfashionable — the modern market has moved toward orangeries and glass extensions.

Conservatories and orangeries are extensions to the main dwelling — they are assessed under the same Householder permitted development rules as any other rear extension: Permitted development (no planning permission required) if: the structure is a single-storey rear addition; it does not exceed the maximum rear extension depth (3m for terraced or semi-detached, 4m for detached, or up to 6m/8m under the prior approval neighbour consultation scheme); it does not exceed 4m in height at any point; it does not cover more than 50% of the original curtilage of the dwelling; and the materials are similar in appearance to the existing dwelling (note: glazed structures are generally assessed as acceptable in appearance terms). Conservation areas: in conservation areas, the same height and depth limits apply, but cladding restrictions mean that the structure must not exceed 3m depth (the neighbour consultation extension to 6m is not available in conservation areas) and the appearance must be considered appropriate. Listed buildings: any addition to a listed building requires listed building consent regardless of size — a conservatory on a listed London property requires a listed building application even if it would otherwise be permitted development. Front additions: conservatories and orangeries at the front of a property always require planning permission.

Whether Building Regulations apply depends on the structure type: True conservatory (as defined above — majority glass roof and walls, thermally separated): exempt from Part L energy efficiency requirements if under 30m². Still subject to Building Regulations for any structural work (new foundations, connections to the main building). Orangery or glass extension (solid roof elements, not thermally separated, or over 30m²): full Building Regulations compliance required, including: Part A (structure) — foundations and structural adequacy; Part C (site preparation and resistance to contaminants) — damp proofing and drainage; Part L (conservation of fuel and power) — energy efficiency of glazed roof, walls, and floor; Part P (electrical safety) — any electrical installation; and Part F (ventilation) — adequate fresh air ventilation. What Part L compliance means for an orangery in London: the glazed roof must achieve a U-value better than 1.8 W/m²K (double or triple glazed units); the glazed walls must achieve U-values better than 1.6 W/m²K; overheating must be controlled (solar control glass or shading is often required); and the new structural walls (if any) must meet the standard thermal insulation requirements. Building Regulations Approval: apply to your local council or an approved inspector before starting an orangery that requires Building Regulations.

The cost range for conservatories and orangeries in London is wide, reflecting the spectrum from basic PVC-framed polycarbonate conservatories to bespoke structural glass orangeries: Basic PVC/aluminium conservatory with polycarbonate or basic double-glazed glass roof (6m x 3m, approximately 18m²): £15,000-£30,000 supply and install. This is the traditional entry-level conservatory — functional but not high-specification. Mid-range aluminium conservatory with glazed roof (6m x 3m): £25,000-£50,000. Aluminium is more durable and more thermally efficient than PVC and allows slimmer sightlines. Orangery with solid lantern roof and masonry walls (6m x 3m): £40,000-£80,000. The masonry walls and solid roof structure with a lantern insert are more expensive to build than a full-glass conservatory. Glass extension / structural glass roof (6m x 3m, bi-fold or slide-and-fold doors): £60,000-£120,000. The premium option — frameless glass with structural glass rooflights, high-performance aluminium frames, and integrated heating. Whole-width rear glass extension across the full width of a London terrace (typically 5-6m x 4-5m): £70,000-£150,000+. Key additional costs in London: foundations (London clay ground conditions can require deeper footings than standard: add £3,000-£10,000 depending on depth required); groundworks and drainage connection; floor finishes inside the new space; and heating integration (underfloor heating is the preferred solution for orangeries and glass extensions: add £3,000-£8,000).

The choice between a true conservatory and an orangery (or glass extension) depends primarily on: Use and liveability: a true conservatory with polycarbonate roof is often too hot in summer and too cold in winter for comfortable everyday use. A well-designed orangery or glass extension with proper insulation, solar control glass, and underfloor heating is comfortable year-round and functions as proper living space. This is the most important practical distinction — an orangery is more expensive but creates genuine additional living space rather than a seasonal garden room. Planning context: in some conservation areas, a full-glass addition may be seen as more appropriate (less dominant visually) than a rendered masonry orangery. In other cases, a more solid orangery structure is seen as more in keeping. Pre-application discussions with the local authority may clarify preferences. Property type: for a large detached house in suburban London with an enclosed garden, a sizeable orangery can be appropriate in scale. For a Victorian terrace in inner London, a smaller glass extension (3m x full width of the house) is typically the appropriate scale. Budget: a basic conservatory is significantly cheaper than an orangery of equivalent size. If budget is the primary constraint, a good-quality aluminium-frame glass conservatory with a proper glazed roof represents a better-quality result than a budget orangery with inferior materials.