Planning Guide · Updated June 2026

Do I Need Planning Permission for a Two-Storey Rear Dormer in 2026?

A standard rear loft dormer is usually Permitted Development if it stays within 50m³ (40m³ terraced) and meets the design limits. But a genuine two-storey rear addition almost always needs full planning permission. Here is exactly how to tell the difference.

Updated June 2026 England PD rules Vetted builders
Get 3 Free Quotes →See PD Rules
By the BestBuilders Editorial Team
Researched, written & fact-checked by our editorial team. Reviewed . How we research & fact-check
✅Reviewed by the BestBuilders editorial team on 17 June 2026. All planning limits, fees and Permitted Development references verified against current 2026 gov.uk and Planning Portal guidance. Editorial standards: /editorial-standards.
Quick Answer

Two-storey rear dormer planning at a glance

A roof-level rear dormer is usually Permitted Development; a two-storey rear addition is not.

  • Rear loft dormer within 50m³ (40m³ terraced): usually Permitted Development
  • On designated land (conservation area, AONB, National Park): planning permission required
  • Genuine extra first-floor + loft storey at the rear: full planning permission required
  • Householder application fee: £258 · Lawful Development Certificate: £103

Permitted Development does not apply to flats, maisonettes or listed buildings. Always confirm with your local planning authority before building.

The Rules

Permitted Development limits for a rear dormer (2026)

To build a rear dormer without a planning application in England, every one of these must be true:

RuleLimit
Added roof volume — detached / semiMax 50m³
Added roof volume — terracedMax 40m³
Set-back from original eavesAt least 20cm
Height vs existing ridgeMust not exceed ridge
Principal (front) elevationNo forward extension
Side-facing windowsObscure-glazed, fixed below 1.7m

Break any single rule and the dormer needs a householder planning application. A two-storey rear addition exceeds these limits by definition because it adds floor area below the roof.

When PD Does Not Apply

4 Situations That Always Need Planning Permission

Designated Land

Conservation areas & AONBs

Dormers are excluded from Permitted Development entirely on designated land. A full planning application is required, and councils often resist visible rear dormers.

Article 4

Removed PD rights

Some councils use an Article 4 Direction to remove Permitted Development on certain streets. Check the Article 4 register for your address before designing.

Two-Storey

Extra storey at the rear

Adding floor area at first-floor level as well as in the loft is a two-storey extension, not a dormer. It needs full householder planning and a Party Wall agreement.

Flats & Listed

No PD at all

Flats and maisonettes have no Permitted Development rights, and listed buildings also need Listed Building Consent. Both require a full application.

50m³
PD volume limit (semi/detached)
£258
Householder application fee
8wk
Typical determination time
£103
Lawful Development Certificate
Related Guides
All planning guides →
Rear Dormer

Rear Dormer Planning 2026

Full Permitted Development rules for a standard rear dormer.

Planning rules ›
Loft Conversion

Loft Planning 2026

When a loft conversion needs planning permission.

Planning rules ›
Cost

Dormer Loft Cost 2026

£45k – £65k

What a dormer loft conversion actually costs.

Full guide ›
Two-Storey

Two-Storey Extension Planning

Planning rules for a two-storey rear extension.

Planning rules ›
Free Quotes

Get Free Dormer & Loft Quotes from Vetted Builders

BestBuilders matches you with up to 3 vetted UK loft and dormer specialists who can handle design, planning and build. Compare real prices — all for free.

Get My 3 Free Dormer Quotes
Takes 60 seconds · No spam · No obligation
Frequently Asked Questions

Two-Storey Rear Dormer Planning FAQs

It depends what you are building. A standard rear loft dormer is usually Permitted Development if within 50m³ (40m³ terraced) and within the design limits. A genuine two-storey rear addition — extra floor area at first-floor and loft level — is not a dormer and almost always needs full householder planning permission.
It must add no more than 50m³ (40m³ terraced) including previous additions, not extend beyond the front roof plane, be set back at least 20cm from the eaves, not exceed the existing ridge height, use similar materials, and have side windows obscure-glazed and fixed shut below 1.7m.
On designated land (conservation areas, National Parks, AONBs), where dormers are excluded from PD; where an Article 4 Direction applies; on listed buildings; on flats and maisonettes; and whenever the dormer exceeds the volume allowance or breaches a design limit.
A householder planning application costs £258 in 2026 and a Lawful Development Certificate costs £103. Add £1,200–£3,000 for architectural drawings and £400–£900 for structural calculations. Determination usually takes around 8 weeks.
Yes. A Lawful Development Certificate (£103) is formal written proof from the council that your dormer is lawful Permitted Development. It protects against enforcement and is almost always requested by buyers and solicitors when you sell.
It can. If the dormer involves work to a shared party wall — common on semis and terraces — the Party Wall etc. Act 1996 applies and you must serve notice two months before starting. This is separate from planning and applies even when the dormer is Permitted Development.
Tell BestBuilders about your project and postcode and we will match you with up to 3 vetted local loft and dormer specialists within 24 hours. Many handle the full package — design, planning or certificate, structural calculations and build. Quotes are free with no obligation.
Sources & Further Reading

Our sources for this guide

Ready to Start?

Plan Your Dormer with a Vetted Specialist

Tell us about your project and we will match you with 3 vetted local builders who can handle planning and build. Free, no-obligation, no spam.

Get My 3 Free Quotes →View All Planning Guides