A summerhouse is a garden building intended for leisure use: reading, entertaining, relaxing in the garden without full exposure to the weather, and enjoying the outdoors year-round. For planning purposes a summerhouse is an outbuilding, and the same permitted development rules that apply to sheds, workshops, and garden rooms govern whether one can be built without a planning application.

Permitted Development for Summerhouses

Under Class E of Part 1 of the General Permitted Development Order, outbuildings including summerhouses are permitted development and do not require planning permission provided they are within the curtilage of a dwellinghouse and meet the following conditions. The summerhouse must not be forward of the principal elevation of the house or to the side of the house facing a highway. It must not exceed 2.5 metres in eaves height. It must not exceed four metres in height with a dual-pitched roof, or three metres with any other roof type. The combined footprint of all outbuildings and extensions on the property must not exceed 50 percent of the curtilage excluding the original house. It must not be used as a separate dwelling.

Most residential summerhouses are modest structures that comfortably meet these conditions. A summerhouse positioned in the rear garden, with a ridge height of around 2.5 to three metres, clearly within the 50 percent coverage limit, can be built without any planning application or notification.

When Planning Permission Is Required

Planning permission is required for a summerhouse that exceeds the height limits, that is positioned in the front garden forward of the principal elevation, that takes the combined outbuilding coverage above 50 percent of the curtilage, or that is at a listed building. In conservation areas and designated landscape areas, the rules are more restrictive and outbuildings visible from a highway may require planning permission even if they would be permitted development elsewhere. Flats and maisonettes do not benefit from the outbuilding permitted development rights.

Using a Summerhouse as a Dwelling

A summerhouse that is equipped and used as a self-contained dwelling, with sleeping accommodation, kitchen, and bathroom, goes beyond the ancillary use that the outbuilding permitted development right covers. Residential use of a garden structure requires planning permission as a new dwelling regardless of the structure's physical size. The planning authority will look at the use, not just the appearance, when assessing whether planning consent is needed.

Building Regulations

Summerhouses up to 15 square metres are generally exempt from Building Regulations as detached outbuildings. Between 15 and 30 square metres, exemption applies if the structure is more than one metre from the boundary. Above 30 square metres, Building Regulations approval is required. Electrical installations in any summerhouse require Part P compliance regardless of the structure's size.

Summary

Most residential summerhouses are permitted development and do not require planning permission, provided they meet the outbuilding height limits, coverage rules, and position conditions. Listed buildings, conservation areas, designated areas, and the use of a summerhouse as a dwelling can all trigger planning requirements. Building Regulations apply to larger structures and to electrical installations.