Permitted development basics
Most houses in England can build a single-storey rear extension without a planning application if it stays within set limits: 3 m deep for semi-detached and terraced houses, 4 m for detached; no higher than 4 m; eaves no higher than 3 m if within 2 m of a boundary; and it must not cover more than half the garden with buildings.
Larger extensions: prior approval
The neighbour-consultation scheme allows 6 m (semi or terrace) or 8 m (detached) if you notify the council first. Neighbours are consulted for 21 days; if nobody objects, or the council decides the impact is acceptable, you get prior approval. Cheshire West & Chester and Cheshire East both run this and it is faster and cheaper than full planning.
Where the rules don't apply
Conservation areas (parts of Knutsford, Nantwich, Chester, Tarporley, Great Budworth and others), listed buildings, flats and maisonettes, and houses where an Article 4 direction has removed the rights. New-build estates sometimes have permitted development removed by condition on the original permission; check the decision notice.
Building regulations still apply
Permitted development only covers planning. Every extension needs building regulations approval for structure, insulation, drainage, fire safety and electrics. We handle the application and inspections.
Get it in writing
Even when no permission is needed, a lawful development certificate (£264) gives you a document that proves it, which matters when you sell. We recommend one on every permitted-development extension we build.