There is no strict minimum distance between a garden room and your fence under UK Permitted Development. You can build right up to the boundary if you want. But the moment any part of the building sits within 2 m of any boundary, the maximum height drops to 2.5 m — which shapes every subsequent design decision.
The 2 m sweet spot
In a large garden where you have the choice, we typically recommend positioning the building at least 2.1-2.5 m from the nearest boundary. That unlocks the taller-roof design options (up to 4 m at ridge), gives you a walkable strip around the back for maintenance, and reduces the risk of overshadowing complaints from neighbours.
Building close to the boundary
- The build is limited to 2.5 m maximum height overall (typically flat or shallow-pitched roof)
- Access for construction is slightly harder — you may need a temporary fence panel removed
- Consider drainage — any water from your roof must not discharge onto neighbouring land
- A 100-150 mm cladding cavity is left between the wall and the fence for airflow