Permitted development for outbuildings
The majority of garden rooms go up under permitted development, so a standalone planning application usually isn't required, though it comes down to the building's height, how close it sits to boundaries, and how much of the garden is already taken up by other outbuildings. The Planning Portal's outbuildings guidance goes into more detail, and checking with the relevant council for a specific property is still worthwhile.
Ancillary use versus a self-contained space
Under permitted development, a garden room is normally treated as space that supports the main house, an office, say, or a gym, rather than a dwelling in its own right. Anyone thinking more along the lines of a self-contained annexe should raise it with the council directly, as the planning treatment changes.
Foundations, drainage and power
Ground conditions vary across the Dorking area, from the chalk and greensand of the Downs to the heavier clay further south around the Holmwoods, and a sloping garden is common in some of the more rural spots near Box Hill and the surrounding villages. A local installer will typically ask to see the plot, or at least good photos and measurements, before confirming the right base and how power will reach it.
Insulation for year-round use
If it's going to be used daily, all year round, solid insulation in the walls, roof and floor, plus double or triple glazing, matters much more than it would for an ordinary shed. Any link to the mains electricity supply needs to be installed and tested by a qualified electrician.
Frequently asked questions
Do garden rooms need planning permission?+
A good many garden rooms are covered by permitted development, within limits on size, height and position, though it comes down to your specific property. Your local council is the one to confirm this with.
Is it possible to sleep in a garden room?+
A garden room built under permitted development is generally treated as an extension of the main house rather than a standalone home. If you're thinking of something more independent, it's best to raise your intended use with the council directly.
Will I need an electrician?+
Yes, connecting to the mains electricity supply is a job for a qualified electrician, who should also test it once it's in.
Useful local links
- Reigate and Banstead Borough Council – Planning — The planning authority covering Reigate and Redhill, a separate borough from Mole Valley.
- Epsom and Ewell Borough Council – Planning permission — The planning authority covering Epsom, a separate borough from Mole Valley.
- Elmbridge Borough Council – Planning permission and applications — The planning authority covering Cobham, a separate borough from Mole Valley.
- GOV.UK – Planning permission: when you need it — Government guidance on when planning permission is required in England and Wales.
- GOV.UK – Party Wall etc. Act 1996 guidance — Government guidance on notifying neighbours and resolving disputes over shared or boundary walls, relevant to attached garage conversions.
- Planning Portal – Garage conversion — National guidance on when planning permission is needed for a garage conversion in England.
- Planning Portal – Outbuildings — National guidance on permitted development rules for garden buildings and outbuildings, including height and coverage limits.