Conservatories are one of the most popular home extensions in the UK, and the majority are built without planning permission under the permitted development rights that apply to extensions of dwellinghouses. Understanding the conditions that must be met to remain within permitted development is important before building work begins.

When a Conservatory Is Permitted Development

A conservatory on a dwellinghouse is permitted development, meaning no planning application is required, when it meets the standard extension permitted development rules. For a single-storey rear conservatory on a detached house, the structure must not extend more than eight metres beyond the original rear wall of the house. For semi-detached and terraced houses the limit is six metres. The conservatory must not exceed four metres in eaves height or four metres in total height. It must not extend forward of the principal elevation of the house or beyond a side elevation that faces a highway. It must not, taken together with all other extensions and outbuildings, cover more than 50 percent of the curtilage of the original house.

For extensions between three and eight metres on detached houses, or between three and six metres on other house types, the prior approval notification procedure applies. This requires written notification to the local planning authority, a 42-day waiting period, and confirmation that the authority has no objections relating to the impact on adjoining properties before work can begin.

When Planning Permission Is Required

Planning permission is required for a conservatory that exceeds the permitted development limits described above, for any conservatory on a flat or maisonette, for a conservatory that extends forward of the front wall of the house, for a side conservatory in a conservation area, and for any conservatory at a listed building. In these cases, a full planning application must be made and approved before work starts.

The Conservatory Exemption from Building Regulations

Historically, conservatories meeting certain conditions, including a substantially translucent roof, separation from the house by external-quality walls, doors, or windows, and an independent heating system, were exempt from Building Regulations. Changes in 2023 introduced energy efficiency requirements for conservatories above thirty square metres. For most standard residential conservatories under thirty square metres that maintain separation from the main house, the exemption broadly continues. Removing the separating doors or walls to integrate the conservatory with the main house removes the basis for the exemption and brings the structure under full extension Building Regulations requirements.

Lawful Development Certificates

For conservatories within permitted development limits, a Lawful Development Certificate from the local planning authority provides formal written confirmation that the structure is lawful without planning permission. This is not required but is a useful document when selling the property, as it removes any future question about whether the conservatory required planning permission.

Summary

Most single-storey rear conservatories on houses in England fall within permitted development and do not require planning permission. Extensions between three and eight metres on detached houses require prior approval notification. Extensions exceeding these limits, conservatories on flats, front or side conservatories in conservation areas, and all works at listed buildings require planning permission. Building Regulations apply when the conservatory is integrated with the main house without adequate separation. Confirming both requirements before construction avoids costly problems.