Loft Conversion Planning Permission

Planning permission information for Loft Conversions in London and Hertfordshire

Loft conversion or Loft Extension is considered to be permitted development not requiring application for planning permission, given that the certain limits and conditions are met.

1. Loft conversions are not permitted development for houses on designated land.

2. To be permitted development any additional roof space created not exceed these volume allowances: 

  • 40 Cubic meters for terraced houses

  • 50 Cubic meters for detached houses and semi-detached houses.

  • Any previous roof space additions, must be included within the volume allowances 

Architecture Drawings Loft Conversions

Example of Lccl Construction Design and Build of Dormer Loft Conversion project in London. Approved by Local Planning Authority.


Example of Lccl Construction Design and Build of Hip to Gable Loft Conversion project in Hertfordshire. Approved by Local Planning Authority.

3. Materials to be similar in appearance to the existing house.

4. Verandas, Balconies or raised platforms are not permitted development. 

5. An extension beyond the plane of existing roof slope of the principal elevation that fronts a highway is not permitted development.

6. No part of extension to be higher than the the highest part of the existing roof.

7. Any side-facing windows must be obscure glazed and non opening unless the parts which can be opened are more than 1.7 meters above the floor of the room in which it is installed.

8. Roof extensions, apart from hip to gable ones to be set back as far as is practicable. At least 20cm from original eves, the 20cm distance is measured along the roof plane. The roof enlargement cannot overhang the outer face of the wall of the original house.

9. Work on a loft or roof may affect wildlife. You need to consider protected species when planning work of this type. Survey may be needed and if wildlife is using the building a licence might be required.

The permitted development allowances described here apply to houses, not flats, maisonettes or other buildings. 

For more information or to receive a design and build quote for your loft conversion project please get in touch with us via email or call us on 020 8037 7332

Have a Building Project?

We offer building services, design services and design & build services combined including:

Loft Conversions & Roofing (all types) Dormer Loft Conversions, Hip to Gable Loft Conversions, L Shape Loft Conversions, Mansard Loft Conversions or Velux Loft Conversions

House extensions all types (single story extensions, double story extensions, rear and side extensions)

Design and Build Total Project Start To Finish

Small House Builders 

We are a specialist in design, building and construction of house extensions, loft conversions and small houses for residential customers.

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Free Advice Call Monday - Friday 9AM - 8PM and Saturdays 9AM - 5PM


Finchley, London Office Location:

3rd Floor, Hathway House, Popes Dr, Finchley, London N3 1QF



020 8037 7332

Office Hours:

Monday to Saturday 8AM - 6PM

Sunday - Closed

Registered company England:

Loft Conversion Company London Limited. Trading as "Lccl Construction" Registration: 11713461

Accreditation, partnerships and planning:

Planning Portal
Lodon and Hertforshire Construction Awards

Lccl Construction. Specialist loft conversion company, house extension builders, architectural design and planning. Design and build construction company from start to finish including architecture, planning, building control, party walls, structural calculations, project management, construction and finishing.

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