Homeowner guide
Attic conversions: when you need planning permission, and the new dormer exemption
Updated 2026-07-18 · checked against the sources below
The attic conversion is the classic case where planning permission is less of an obstacle than people fear - and building regulations more of one. Works affecting only the interior of a house are exempt from planning outright. The complications start at the roofline: dormers and front rooflights have needed permission - until 27 July 2026, when new exemptions for both commence. Here is the full picture.
The conversion itself: no permission needed
Section 4(1)(h) of the Planning and Development Act 2000 exempts works that affect only the interior of a structure, or that do not materially affect its external appearance. Flooring, insulation, a new staircase, storage - the interior conversion itself is exempt from planning permission, full stop.
Rooflights to the rear are commonly accepted by councils under the same principle, as not materially affecting external appearance - though practice has varied by authority, which is exactly the grey area the 2026 regulations now tidy up at the front of the house.
Dormers and front rooflights: what changes on 27 July 2026
Until 26 July 2026, a dormer generally needs planning permission, and front rooflights sit in council-by-council grey territory. From 27 July, S.I. 344 of 2026 commences two new exemptions:
- Class 1B: a dormer to the side or rear of the roof, up to 30 m³ internal volume, kept below the ridge line and set back at least 20 cm from the eaves. Front dormers still need permission.
- Class 1C: up to two rooflights on the front roof slope, each no larger than 100 cm x 90 cm.
- The usual carve-outs apply: protected structures and architectural conservation areas can lose these exemptions under article 9, and a Section 5 declaration (EUR 80) settles any doubt.
Building regulations: the part that decides if it is a bedroom
Planning exemption does not touch the building regulations, and for attics they are the real test. A habitable attic room must meet the regulations on structure (the existing joists are usually ceiling joists, not floor joists), fire safety (escape provision and a protected stairway), stairs, insulation and ventilation.
This is why estate agents distinguish a converted attic from an extra bedroom: a conversion that never went through building-regulations compliance is typically marketed as non-habitable storage space, whatever it is used as. If the goal is a room that counts - for daily life or resale - build it to the regulations and keep the paperwork. An extension built under a permission needs a commencement notice; a planning-exempt internal conversion does not, but the regulations still bind and a surveyor will ask questions at sale time either way.
Attic conversion or dormer extension: a quick decision frame
If headroom works without altering the roof, the conversion is planning-free today. If you need a dormer for headroom or light, to the side or rear, waiting for 27 July 2026 makes it planning-free within the new limits - a real saving in time and fees. A front dormer, or anything on a protected structure, remains an application. And if the attic cannot give you a compliant habitable room at all, the extension and garden-room guides cover the alternatives.
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Quick answers
Do I need planning permission for an attic conversion?
Usually no - works affecting only the interior are exempt under section 4(1)(h) of the Planning Act. Permission enters the picture only when you alter the roofline: dormers, or rooflights to the front (both of which gain new exemptions from 27 July 2026).
Do I need permission for a dormer?
Until 26 July 2026, generally yes. From 27 July 2026, a side or rear dormer up to 30 m³, below the ridge and set back 20 cm from the eaves, is exempt. Front dormers still need permission.
Can I put a Velux window on the front roof?
From 27 July 2026, up to two front rooflights of up to 100 cm x 90 cm each are exempt. Before that date, front rooflights are a council-by-council judgment - many treat them as needing permission.
Will a converted attic count as a bedroom when I sell?
Only if it complies with the building regulations - fire escape, protected stairs, structure, insulation. Planning exemption alone does not make it habitable space; a non-compliant conversion is typically marketed as storage. Keep certificates from a registered professional if you want the room to count.
Sources
Related
General guidance, not legal or planning advice. The regulations and your local authority's interpretation bind; conditions and local rules (protected structures, architectural conservation areas, flood zones) can change the answer for a specific property. When in doubt, ask your council for a Section 5 declaration or talk to a planning consultant.