What is a garden room? The definition, and how it differs from a summerhouse

A garden room is built like a small timber-framed house: insulation in the floor, walls and roof, a membrane that controls moisture inside the structure, house-quality double glazing and a dedicated electrical supply from the house. A summerhouse or log cabin is mostly solid timber, built for the warmer months.

Once the cladding is on, a well-specified garden room and a poorly specified one can look identical. The difference shows in winter, in how warm the room stays and what it costs to heat. That is why the most useful question to ask any company is for the U-values of the roof, walls and floor: the rate at which each one loses heat, where a lower number is better.

A company that quotes insulation only in millimetres should be able to translate it into U-values. Thickness says little without knowing the material.

Another word for a garden room. Garden studio, garden office and garden pod are the names used most often, usually describing the use or a compact size. In planning documents the building is an outbuilding.

The same building can be set up for very different uses, and the use decides which details matter. A garden office needs good insulation and a broadband connection. A gym needs a reinforced floor, at least 2.4m of internal height and good ventilation. A music room needs acoustic insulation, and professional recording needs a specialist.

Two uses change the rules. Working alone at a desk counts as incidental to the house, but a business with regular client visits, such as a salon or clinic, may need planning permission for that use. A room used for sleeping, even occasionally, must meet Building Regulations and in most cases needs planning permission as well (see garden bedrooms). A self-contained annexe, with its own kitchen and bathroom, is a different category with its own approval routes (see garden annexes).

Most garden rooms now stand on ground screws, which go in the day the frame goes up, need no concrete and can be removed cleanly at the end of the building’s life. Concrete pads, pre-formed plinths and full slabs are the alternatives, and the right one depends on the ground, which is why a site survey comes before any order.

In our October 2026 survey of 42 UK companies’ published prices, a typical 3m × 3m room costs about £19,700 and a 5m × 3m about £25,500, including VAT and installation.

Size is the biggest factor, and small rooms cost more per square metre because the doors, windows and electrics cost much the same at any size. Prices for similar rooms also vary by up to 100% between companies. Three costs are often left out of a headline price: the electrical connection from the house (typically £1,500–£3,500, depending on the distance), foundations if they are not included (from about £1,000 to £6,500 or more, depending on the size of the room, the type of foundation and the ground), and delivery beyond a set distance.

Most garden rooms are built under Permitted Development, which means no planning application is needed as long as the building stays within set limits. The one that shapes most designs is height: within 2m of a boundary, the building can be no taller than 2.5m, which is why so many garden rooms are exactly that height. Further from the boundary, it can be up to 3m with a flat or mono-pitched roof, or 4m with a dual-pitched roof.

Permitted Development doesn’t apply everywhere. Listed buildings, conservation areas, National Landscapes (formerly AONBs) and National Parks have tighter rules, and some homes have had the rights removed. Where it does apply, a Lawful Development Certificate from the council confirms in writing that the building is lawful, which helps when the house is sold. The rules here are for England. Wales is similar, while Scotland and Northern Ireland have their own (see planning in all four nations).

Building Regulations don’t usually apply to a garden room, with three exceptions: a room over 30sqm, a room used for sleeping, and a room over 15sqm within 1m of a boundary, which must be built largely from non-combustible materials. The electrical installation always needs signing off by a qualified electrician.

The cladding makes the biggest difference. Cement fibreboard and good composite boards last longest with the least upkeep. Western red cedar and Siberian larch can be left untreated to weather to silver-grey and typically last 30–40 years or more. Treated softwood looks good when new but needs re-treating every three to five years, and lasts around 20–25 years with that care.

Most people buy directly from a garden room company, which designs the room, supplies it and installs it with its own team. Kits sold online have the lowest headline prices, but the foundations, electrical connection, installation and finishing are usually extra, so compare the full cost. Some firms design a bespoke room and have it built by a third-party manufacturer, which can suit an unusual project but adds their margin.