Orangery Calculator — Columns, Lantern Roof & Glazing

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).

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.

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.

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.

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.