What is the 1 metre boundary rule?

In building regulations, the space between your wall and the boundary determines how much fire protection that wall needs. Within 1 metre, the wall must achieve set fire resistance and the area of "unprotected" openings — windows and doors — is tightly limited. This is why extensions built close to the line often have solid flank walls.

The 1 metre figure is frequently muddled with two different planning rules: the permitted development limit that caps eaves at 3 metres when an extension comes within 2 metres of a boundary, and the 2.5-metre height cap for outbuildings within 2 metres of a boundary. Different rules, different distances, different consequences.

There's also a practical, non-statutory version: builders and designers often recommend keeping around a metre clear of the boundary so gutters don't overhang next door's land (which is a trespass) and so the wall can be maintained without needing neighbourly goodwill or an access agreement.

None of these rules stops you building close to the boundary — they change what the building must be. Solid construction near the line, party wall notices where the Act applies, and a design that doesn't loom over the neighbour's garden.

If your project involves any boundary-hugging construction, confirm both regimes early: the planning position (permitted development or application) and the building regulations position. They're separate approvals and satisfying one doesn't satisfy the other.