A garden room is one of the most popular ways to add extra space at home without the cost and disruption of a house extension, and the good news is that most garden rooms can be built without needing full planning permission. That said, the rules are specific, and getting them wrong can mean a costly redesign or a planning enforcement issue further down the line. This guide sets out the permitted development rules that apply to garden rooms in England, based on current national planning guidance, so you know where you stand before you start designing.
What counts as permitted development for a garden room?
Garden rooms are treated as outbuildings under Class E of the Town and Country Planning (General Permitted Development) (England) Order, which covers buildings that are "incidental to the enjoyment of the dwellinghouse" rather than used as separate, self-contained living accommodation. This covers uses such as a home office, gym, studio, playroom or hobby space. Provided your garden room meets the conditions below, it will typically not need a planning application.
Height limits
Height is one of the most important rules to get right. If any part of the garden room sits within 2 metres of a boundary of your property, the maximum overall height allowed under permitted development is 2.5 metres. Move further than 2 metres from the boundary, and the height limit rises to 4 metres for a building with a dual-pitched roof, or 3 metres for any other roof type, such as a flat or mono-pitched roof. This is why many garden rooms are designed with a flat or low-pitched roof when they sit close to a boundary, to maximise usable internal height within the 2.5 metre limit.
Position in the garden
A garden room must be sited behind the principal elevation of the house, meaning you cannot normally build one in your front garden under permitted development; a garden room in front of the house would need a full planning application. It must also be single storey, so garden rooms with a usable upper floor or mezzanine that increases the overall height beyond the limits above will not qualify.
The 50% garden coverage rule
Permitted development rights limit how much of your garden can be covered by outbuildings in total. All existing and proposed outbuildings and extensions combined, including sheds, garages, conservatories and summerhouses, must not cover more than 50% of the land around the original house, excluding the footprint of the house itself. If your garden already has a shed, garage conversion or previous extension, this needs to be factored into whether a new garden room still fits within the 50% limit.
When do you need planning permission for a garden room?
Full planning permission is more likely to be needed if any of the following apply:
- Your property is a listed building, where permitted development rights do not apply in the same way and any changes need separate listed building consent
- Your property is in a conservation area, National Park or Area of Outstanding Natural Beauty, where outbuilding rules are often more restrictive, including on outbuildings more than 20 metres from the house
- Permitted development rights have been removed from your property, which can happen on some newer housing developments through a planning condition
- You want to position the garden room in front of the house
- The garden room would exceed the height, coverage or boundary rules set out above
- You intend the garden room to be used as separate, self-contained living accommodation rather than ancillary space, such as a space with its own kitchen and bathroom that could function as a separate dwelling
Where there is any doubt, it is possible to apply to your local planning authority for a Lawful Development Certificate, which formally confirms that a project does not need planning permission. We can advise on whether this is worth doing as part of your free quote.
Do garden rooms need building regulations?
Planning permission and building regulations are two separate things, and a garden room not needing planning permission does not automatically mean building regulations do not apply. A garden building is generally exempt from building regulations if its floor area is less than 15 square metres and it contains no sleeping accommodation. Between 15 and 30 square metres, it can still be exempt provided it contains no sleeping accommodation and is either at least 1 metre from any boundary or built substantially from non-combustible materials. Garden rooms over 30 square metres, or any size intended for sleeping accommodation, will usually need full building regulations approval, covering structural stability, insulation, electrical safety and fire precautions. We assess this for your specific garden room as part of your design and quote.
Checking your own property
These are the general national rules for permitted development in England, but individual properties can differ, particularly where a planning condition has removed permitted development rights, or where local designations apply. Before finalising any garden room design, we check the specifics of your property and postcode, so you know exactly where you stand before committing. If you are weighing up a garden room against a house extension, our guide to garden room vs house extension compares the two in more detail, including cost and timescale.
About HK Builders
HK Builders Ltd is an FMB-registered, fully insured, family-run building company based in Solihull, with over 20 years of experience building garden rooms and extensions across Solihull and the West Midlands, including Dorridge, Knowle, Shirley, Sutton Coldfield, Harborne, Moseley, Coventry and Redditch. As our reviews show, we handle planning and building regulations for clients from the first conversation. Explore our garden rooms page for the full range of what we build, or get in touch for a free, no obligation quote.
Call 07393 194 336Get a free quote
Frequently asked questions
Do I need planning permission for a garden room?
How close to the boundary can I build a garden room?
Does a garden room need building regulations approval?
Can I live in a garden room full time?
Guides worth reading
Guides from the HK Builders blog on garden rooms, costs and planning permission.
