Double Storey Extension Planning Permission
Most two storey extensions in England need a householder planning application. A small rear extension can go ahead without one, but only inside limits that rule out most bedroom-sized plans.
£548householder application in England, from 1 April 2026
Why an upper floor usually needs an application
Permitted development lets you extend a house without applying, within set limits. For anything taller than one storey the limits are tight, and a few routes are closed altogether.
The larger home extension prior approval scheme, the one that allows deeper rear extensions after neighbours are consulted, covers single storey extensions only. It cannot be used for two floors. A side extension of more than one storey is not permitted development either, so every two storey side extension in England needs planning permission.
The permitted development limits for a two storey rear extension
If you want to build without an application in England, the extension has to meet all of these, as set out in the GOV.UK permitted development technical guidance:
- It sticks out no more than 3 m beyond the house's original back wall.
- It keeps 7 m or more clear of the garden boundary facing that back wall.
- The roof pitch matches the existing house as far as practicable.
- Upstairs windows in a side wall have obscure glass and cannot open, except for any part that sits over 1.7 m up from the floor.
What 3 m deep buys you
Measured outside, 3 m leaves a room upstairs roughly 2.6 m deep once the walls are allowed for. Across the width of a typical semi that is a single bedroom or a snug double, with a deeper kitchen below. That suits some houses. Most families who want a double bedroom with a shower room, or a kitchen with space for a table, end up deeper than 3 m, and so end up applying.
The 7 m rule catches short gardens. Measure from the back wall of the house to the rear fence before you draw anything.
Flats and maisonettes get no householder permitted development at all. On designated land, such as a conservation area, the limits differ, and listed buildings need their own consent for most alterations. The GOV.UK guidance sets out each case.
Which route fits your plan
| Route | When it fits a two storey extension | Fee in England |
|---|---|---|
| Permitted development | At the back only: up to 3 m out from the original back wall, 7 m kept clear to the rear boundary, window and roof conditions met | None (a lawful development certificate is optional, at half the application fee) |
| Householder planning application | Anything deeper, any side extension, and anything on designated land | £548 |
| Larger home extension prior approval | Not available: single storey extensions only | Does not apply |
Fees are the MHCLG figures from 1 April 2026. This is general guidance, not legal advice.
Approved drawings or just an idea, a firm can price both floors from rough sizes.
Get a quoteMaking a householder application
The application goes to your council, usually through the Planning Portal. In England the fee is £548. You send floor plans and elevations for both floors, a site location plan and a block plan. The council tells the neighbours, and the target for a decision is eight weeks.
For an upper floor, the questions the planning officer asks are about the neighbours: whether a first-floor window looks into their garden, whether the new wall takes light from their windows, and whether it looms over them. Many councils publish a householder design guide with their own rules of thumb for two storey extensions near a boundary. Read yours before the drawings are finished; it is the quickest way to avoid a refusal.
If you are inside the limits
No application is needed, but a lawful development certificate is still a good idea. It confirms the extension is permitted development, which buyers' solicitors and lenders like to see. It costs half of what a householder application costs. See GOV.UK on lawful development certificates.
Prefab changes nothing for planning
Planning looks at the finished building, not how it was made. A two storey extension built from factory panels or modules faces the same limits and the same application as one built in brick. What helps is that most prefab firms draw to fixed panel or module sizes, so the drawings are often ready quickly.
Matching materials still matter. A timber or SIPs frame can carry brick slips, render or real brick on the outside, so the extension can match the house.
Building regulations are a separate approval
Planning and building regulations are separate approvals, and a two storey extension needs building control sign-off whichever planning route it takes. Building control looks at the structure, fire escape from the new bedroom, the stairs, insulation and drainage. See GOV.UK on building regulations approval.
Scotland and Wales
Scotland has its own householder permitted development rules, set out in Scottish Government Circular 1/2024, and building cannot begin before the council grants a building warrant. Wales also has its own rules; see the Welsh Government guidance for householders. In both, planning fees are set nationally, so check the current fee when you apply.
Questions families ask
Can I build a two storey extension without planning permission?
Only at the back, and only if it sticks out no more than 3 m from the original back wall, leaves 7 m to the rear boundary, matches the roof pitch and has obscure, fixed side windows upstairs. Anything else needs an application.
Does a two storey side extension need planning permission?
Yes, in England. Side extensions of more than one storey are outside permitted development, so you need a householder application.
How long does planning take for a double storey extension?
The target is a decision within eight weeks of a valid application. The drawings come before that, so allow time for them as well.
Read next
- Double storey side extensions
Always an application in England, and the design points councils look for.
- 2 storey extension cost
The calculator, with planning and building control fees.
- Fire escape window regulations
What a new upstairs bedroom needs under building regulations.
Get a quote for your two storey extension
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