What is the difference between an orangery and a conservatory?

An orangery has substantial brick or stone columns/piers with glazing between them, a flat roof perimeter with a glazed lantern in the centre. A conservatory is primarily a glass structure. Orangeries feel more like a room of the house, are better insulated and are treated as extensions (full Building Regulations apply).

Does an orangery need Building Regulations?

Yes. Unlike some conservatories, an orangery is always subject to Building Regulations because it has a solid roof (the flat perimeter). It is treated as a standard extension and must comply with Part L (insulation), Part B (fire), Part F (ventilation) and all other relevant parts.

What is a lantern roof?

A lantern roof is a raised glazed section in the centre of a flat roof that allows natural light into the orangery. It typically covers 30–50% of the total roof area. The lantern has its own ridge and pitched glazing panels. Standard sizes range from 1.5m x 1m to 3m x 2m or larger for bespoke designs.

How much does an orangery cost?

Orangeries typically cost £2,500–£4,000 per m² depending on specification, making them more expensive than conservatories but comparable to a high-quality extension. A 15m² orangery might cost £35,000–£60,000. The brick columns, lantern roof and structural beam add cost over a standard conservatory.

Do orangery brick columns need foundations?

Yes. The brick columns carry significant structural load (they support the perimeter beam and flat roof). They need proper pad or strip foundations designed by a structural engineer. Foundation depth depends on soil type but is typically 600mm–1m minimum for the columns.

TradeCalculator

Orangery Calculator — Columns, Lantern Roof & Glazing

Calculate orangery dimensions including brick columns, lantern roof area, glazing infill panels, structural beam span and flat roof perimeter.

Orangery length

Orangery width (depth)

Number of brick columns

Glazing panels

Avg panel width

Avg panel height

How We Calculate This

This calculator estimates key dimensions and material quantities for an orangery based on overall plan size and configuration.

Roof split

Total roof area is divided into the lantern (glazed, central) and the flat roof perimeter (insulated, solid). The flat roof perimeter requires insulation to U-value 0.15.

Structure

Brick columns support the perimeter beam. A structural steel or aluminium beam spans between columns across the front. Glazing panels fill the spaces between columns.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.