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Additional storey (upward extension): do I need planning permission? (England, 2026)

For homeowners in England. Updated 2026-06-17.

Overview

Adding a storey on top of a house can be permitted under the Class AA upward-extension right, but only through prior approval and only within a tight age and height window.

The permitted-development rules

Class AA goes through prior approval, never bare permitted development. The house must have been built after 1 July 1948 and before 28 October 2018, be off designated land and not listed, stay within overall height limits (18m) and roof-height increases (+3.5m for one storey, +7m for more). Otherwise a full application is required.

Whether these rules apply to your home depends on any conservation area, Article 4 direction or listed-building status at your address. Check yours below.

Building regulations (separate from planning)

An additional storey creates new habitable storeys, so the full suite of building regulations applies — and it is more demanding than an extension:

  • Part A — Structure: The existing structure and foundations must carry the new loads, and underpinning may be needed — usually the single biggest engineering issue.
  • Part B — Fire safety: A new top floor more than 4.5m above ground triggers a protected stairway and means of escape — fire doors and interlinked mains alarms; escape via upper-floor windows is no longer acceptable.
  • Parts L, K, F, P: Energy/thermal, stairs and headroom, ventilation and electrical safety all apply to the new storey.
  • Part E — Sound: On terraces and semi-detached houses, improved party-wall sound insulation may also be required.

Check your planning route

Answer a few questions about your home and your plans. No email or sign-up — your verdict shows straight away.

  1. 1 Postcode
  2. 2 Property
  3. 3 Plans
  4. 4 Details
  5. 5 History
What's your postcode?

We use it once to look up your borough and the planning record — it isn't stored with your details.

Frequently asked questions

Can I add a storey to my house without planning permission?
Not without prior approval. The Class AA right lets you add up to two storeys to a house of two or more storeys (one storey on a single-storey house), but only through a prior-approval application — never bare permitted development — and only within strict age, height and location limits. Otherwise a full application is required.
What is Class AA, and do I need prior approval to add a storey?
Class AA is the permitted-development right for upward extensions. It always goes through prior approval, where the council assesses matters such as external appearance and impact before you build. The Planning Portal gives a default determination period of about 8 weeks. Prior approval cannot be obtained retrospectively — secure it before work starts.
Which houses can’t be extended upwards under permitted development?
Class AA excludes houses built before 1 July 1948 or after 28 October 2018, houses on designated land (conservation areas, AONBs, National Parks, World Heritage Sites) or an SSSI, houses already extended upward, and homes created through certain change-of-use rights. Listed buildings need listed-building consent in any case.
Can I extend my Victorian house upwards under permitted development?
No. A Victorian house was built before 1 July 1948, which falls outside the Class AA age window (built after 1 July 1948 and before 28 October 2018). An upward extension on a Victorian house therefore needs a full planning application — and listed-building consent if it is listed.
How high can I extend my house upwards?
Class AA caps the highest part of the new roof at 18 metres. The height increase itself must not exceed 3.5 metres for a one-storey house, or 7 metres for a house of more than one storey. Materials must match the existing house, and no windows are allowed in a side-facing wall or roof slope.
Does adding a storey need building regulations?
Yes — the full suite. You are creating new habitable storeys, so structure is critical: the existing foundations must carry the load, and underpinning may be needed (Part A). A top floor above 4.5m triggers a protected stairway and means of escape (Part B). Energy, stairs, ventilation, electrics and party-wall sound also apply.
Sources and legal currency

Legal currency (mid-2026): GPDO 2015 householder Class A (extensions) and Class B (roof/loft) limits are unchanged — SI 2025/560 and SI 2026/313 did not amend them. The operative energy standard is the 2021 Part L uplift (in force 15 June 2022); the Future Homes Standard is delayed (the Building Regulations etc. (Amendment) (England) Regulations 2026 come into force 24 March 2027). Confirm exact U-values against the current Approved Document L at the point of build.

Other extension types

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