Permission guide for a dormer or roof extension
Planning permission is normally not required for a compliant rear dormer, but a front dormer or oversized roof extension normally needs permission.
Total extra roof space is generally limited to 40m³ for terraces and 50m³ for detached or semi-detached houses.
Why?
- A dormer must fit the specific roof-enlargement right.
- Previous roof additions count towards the allowance.
Important: planning rules and permitted-development rights differ across England, Wales, Scotland and Northern Ireland. Check the rules for the nation in which the property is located. Local restrictions, listed status, property type and planning history can also narrow or remove normal rights.
What should I check?
- Measure added roof volume and height
- Check which roof slope faces a highway
- Include earlier roof additions
- Consider overlooking and protected areas
Could permitted development apply?
Possibly. A permitted-development right can grant planning permission for a qualifying proposal, but only when every applicable limitation and condition is met. Some routes also require prior approval before work starts. If no suitable right or other consent route applies, an application may be needed.
When does the answer change?
Pause and ask the authority if the site or building is listed, lies in a conservation area, National Park or other designated area, is affected by an Article 4 direction or restrictive planning condition, or has an uncertain planning history. If you are relying on householder permitted-development rights, also confirm that the property is a house rather than a flat or maisonette.
A similar project nearby is not proof that yours is permitted. Measurements, property type, earlier work and restrictions may be different.
Other approvals
Building regulations, structural design, party-wall matters and protected-species rules may apply.
Maps and drawings for a dormer or roof extension
If the authority asks for an application, prior approval, formal certificate or another consent, it will specify the plans and supporting information required. A location plan normally identifies the site; a block or site plan and other drawings can explain the proposal where relevant.
- A location plan with the correct site boundary where required
- A block or site plan when the proposal changes the site layout
- Existing and proposed drawings, photographs or supporting details as relevant
- Access and neighbouring features where they affect the proposal
Confirm the answer locally
Ask the planning authority for the site about local restrictions and how to obtain written or formal confirmation.
Planning rules depend on the exact property, proposal, location and planning history. For advice you can rely on, contact your planning authority or a planning professional.
Questions about a dormer or roof extension
Do I need planning permission for a dormer or roof extension?
Planning permission is normally not required for a compliant rear dormer, but a front dormer or oversized roof extension normally needs permission. A dormer must fit the specific roof-enlargement right. Previous roof additions count towards the allowance.
Could a permitted-development or other consent route apply to a dormer or roof extension?
Possibly. The correct route depends on the proposal and location; all relevant limitations, conditions, notification and prior-approval requirements must be met.
How can I obtain a definite answer?
Ask the planning authority about written advice, pre-application advice or the relevant formal certificate process before starting work.