House Extensions Finchley N3 & N12 2026: Complete Guide to Costs, Planning and Types

Finchley is LCCL Construction's home territory. Our offices are based in Finchley N3 and we have delivered more house extensions and loft conversions in Finchley than any other area. The N3 and N12 postcodes encompass Finchley Central, North Finchley and East Finchley — areas characterised by a mix of Edwardian semi-detached houses, inter-war detached properties and Victorian terraced houses that offer excellent opportunities for house extensions of all types. LCCL Construction delivers house extensions across all of Finchley as part of our complete design and build service.

LCCL Construction — based in Finchley N3, specialist house extension builders across Finchley and North London

House Extensions Finchley: Best Types for Local Properties

The large Edwardian semi-detached houses that are common across Finchley N3 and N12 are ideally suited to wraparound extensions and double storey rear extensions. Victorian terraced houses in the area suit rear extensions and side return extensions. The detached inter-war and post-war properties in North Finchley and Whetstone suit generous rear extensions and double storey side extensions. LCCL Construction's deep knowledge of Finchley's property types and planning authority means we can advise on the best extension type for your specific property.

How Much Do House Extensions Cost in Finchley in 2026?

Rear extension: £37,000 to £70,000.

Side return: £37,000 to £70,000.

Wraparound: £63,000 to £107,000.

Double storey: £83,000 to £142,000.

All include architectural design, planning permission, building regulations, structural calculations, party wall agreements, construction and finishing.

See our full house extension cost guide.

Planning Permission for House Extensions in Finchley

Most single storey rear extensions in Finchley fall within permitted development rights. However Finchley has several conservation areas including the East Finchley Conservation Area and parts of Finchley Central where planning permission is required. LCCL Construction checks all planning requirements as part of the free consultation. See our guide to house extension planning permission in London.

Why Choose LCCL Construction for House Extensions in Finchley?

LCCL Construction is based in Finchley N3 — we are the truly local specialist. Our team has unparalleled knowledge of Finchley's property types, planning authority, building control, local suppliers and access routes. We have completed more projects in Finchley than any other area and have a deep portfolio of completed extensions across N3 and N12. Over 20 years experience. 200+ reviews at 4.7/5. LABC Award Winners 2024. LABC Registered Partners. NFB members.

Areas of Finchley and Surrounding North London We Cover

LCCL Construction covers all areas of Finchley and surrounding North London including Finchley Central N3, North Finchley N12, East Finchley N2, Finchley Road NW3 NW11, Whetstone N20, Totteridge N20, Woodside Park N12, Friern Barnet N11, Colney Hatch N11, Mill Hill NW7, Hendon NW4, Golders Green NW11, Barnet EN4 EN5 and all surrounding postcodes.

Frequently Asked Questions About House Extensions in Finchley

How much does a house extension cost in Finchley?

Costs range from £37,000 for a small single storey rear extension to £142,000 for a large double storey extension with high specification finishes. A typical rear extension costs £37,000 to £70,000.

Is LCCL Construction based in Finchley?

Yes — LCCL Construction is based at Hathaway House, Popes Drive, Finchley N3. We are the local specialist with the deepest knowledge of Finchley's property types and planning authority.

To get a free consultation call LCCL Construction on 020 8037 7332 or get an instant quote online.