Do you need planning permission for a garden room?
In most cases, no. Here are the four numbers that decide it, plus the situations where the answer changes.
The short answer
The overwhelming majority of garden rooms are built under permitted development, which means no planning application at all. Outbuildings are treated as “incidental” to your house, and as long as you stay inside a handful of limits, you don’t need to ask permission to build one.
The four numbers that matter
Height within 2m of a boundary: 2.5m maximum, measured from the highest adjacent ground. Height elsewhere in the garden: 4m for a dual-pitched roof, 3m for anything else, with eaves no higher than 2.5m. Coverage: outbuildings must not take up more than half the land around the original house. Position: nothing forward of the principal elevation.
Where it gets more complicated
Listed buildings need consent for almost anything. Conservation areas restrict outbuildings to the rear and cap the size. Some properties, particularly newer estates and flats, have had permitted development rights removed by an Article 4 direction or a planning condition on the original build. And if you plan to sleep in it or run a business with visiting customers from it, the “incidental use” test starts to wobble.
Building Regulations are a separate question
Planning and Building Regs are two different systems, and people conflate them constantly. A garden room under 15m² generally needs no Building Regs approval. Between 15 and 30m² it’s still exempt provided it sits at least a metre from any boundary or is built from substantially non-combustible material. Over 30m², or with sleeping accommodation, Building Regs apply. Electrical work always needs to be certified regardless of size.
What we do about it
We check your property’s planning history, designations and permitted development rights at the free survey, before you commit to anything. If an application is needed, we prepare and submit it. If we think your plan won’t fly, we tell you then rather than after you’ve paid a deposit.
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