Permitted development checker
Answer six quick questions to see whether a two-storey extension is likely to need planning permission where you live.
What this checker does and doesn't do
It applies the headline permitted development tests for extensions of more than one storey in each nation, using the rules in force on 9 November 2026. It can't see your title, planning history or the exact shape of your house, so treat the result as a starting point. For certainty, apply to the council for a lawful development certificate (a certificate of lawfulness in Scotland and Northern Ireland) before you build.
The headline rules
- England: In England, a two-storey rear extension can be permitted development if it goes no more than 3 m beyond the original rear wall, stays at least 7 m from the rear boundary, matches the house's materials and roof pitch, and the house is not in a conservation area, National Landscape, National Park, World Heritage Site or the Broads. Two-storey side, wraparound and front extensions always need planning permission.
- Wales: In Wales, a two-storey rear extension can be permitted development if the ground floor goes no more than 4 m and the first floor no more than 3 m beyond the original rear wall, and the first floor stays at least 10.5 m from the rear boundary. Unlike England, a two-storey side extension can also be permitted development if it is at least 10.5 m from the side boundary, set back at least 1 m from the front and doesn't widen the house by more than half. None of this applies in conservation areas, National Parks, National Landscapes or World Heritage Sites.
- Scotland: In Scotland, a ground-floor extension of more than one storey (Class 1B) can be permitted development only if no part of it is within 10 m of any boundary of the plot, it is no higher than the house, and the house is not in a conservation area or a flat. On most suburban plots that 10 m test means a two-storey extension needs planning permission.
- Northern Ireland: In Northern Ireland, a two-storey rear extension can be permitted development if it goes no more than 3 m beyond the original rear wall and stays at least 7 m from the rear boundary, with height, materials and roof-pitch conditions, and not in specified protected areas. Most side and front two-storey extensions need planning permission.
More detail: permitted development in England, Wales, Scotland and Northern Ireland.
Questions people ask
Can a two-storey extension be permitted development?
Sometimes. In England and Northern Ireland a two-storey rear extension can be, if it is no more than 3 m deep and at least 7 m from the rear boundary. Wales allows 3 m upstairs with 10.5 m to the boundary, and some side extensions. In Scotland every part must be 10 m from all boundaries.
What is a lawful development certificate?
A certificate from the council confirming that a proposed extension is lawful under permitted development. It isn't compulsory, but it gives you and future buyers certainty. In England it costs £274 (about £288 for applications from 8 December 2026).
Does permitted development mean I don't need building regulations?
No. Permitted development only covers planning. You still need building regulations approval (a building warrant in Scotland) for a two-storey extension.
Ready to see what a second storey could do for your home?
Book a free site visit. We'll look at your house, talk through options and explain the approvals you'd need, then price the design stage in writing.