House Extensions & Loft Conversions in Muswell Hill

LCCL Construction is a design and build company based in Finchley N3, working in Muswell Hill for over 20 years. One team, one contract: architects, structural engineers, project managers and builders coordinated by LCCL take your project from first sketch to handover.

Muswell Hill's Edwardian terraces and semis (the Rookfield and Fortis Green streets especially) have generous roofs for rear dormers and mansards and long rear gardens for side-return and rear kitchen extensions. Much of it is conservation area, so detailing matters.

What it costs in Muswell Hill

The final figure depends on postcode, access and site conditions — the instant estimate applies your area. Guide ranges for 2026, design and build inclusive (architecture, structural engineering, planning or LDC, construction, project management and building control). Every project is surveyed and priced individually.

• Velux loft: £32,400 – £50,400 inc. VAT (£27,000 – £42,000 + VAT)
• Rear dormer loft: £56,400 – £80,400 inc. VAT (£47,000 – £67,000 + VAT)
• L-shaped dormer: £58,800 – £98,400 inc. VAT (£49,000 – £82,000 + VAT)
• Hip to gable: £60,000 – £114,000 inc. VAT (£50,000 – £95,000 + VAT)
• Mansard: £76,800 – £148,800 inc. VAT (£64,000 – £124,000 + VAT)
• Rear extension: £42,000 – £90,000 inc. VAT (£35,000 – £75,000 + VAT)
• Side return: £42,000 – £93,600 inc. VAT (£35,000 – £78,000 + VAT)
• Wraparound: £72,000 – £153,600 inc. VAT (£60,000 – £128,000 + VAT)
• Double storey: £90,000 – £198,000 inc. VAT (£75,000 – £165,000 + VAT)

Kitchen on top of the structure, supplied and fitted: +£9,000 – £87,360 inc. VAT (£7,500 – £72,800 + VAT) depending on size and specification. Basements: cellar refit £54,000 – £114,000 inc. VAT (£45,000 – £95,000 + VAT), lowering £114,000 – £216,000 inc. VAT (£95,000 – £180,000 + VAT), new dig £216,000 – £360,000 inc. VAT (£180,000 – £300,000 + VAT)+. New build: £2,200 – £4,500 per sqm (zero-rated for VAT).

Recent LCCL projects near Muswell Hill

Uplands Road, Crouch End N8 — double-storey extension

A two-storey extension on a 1930s semi in Crouch End: open-plan kitchen below, a new bathroom and study above, finished with Lusso Stone, Buster + Punch and column radiators.

See the project

Also nearby: Cumberland Road, Wood Green N22 (l-shaped loft, 2022) · Manor Park Road, East Finchley N2 (side return extension, renovation, 2024).

Planning in Muswell Hill

Haringey; the Muswell Hill and Rookfield conservation areas mean planning permission for dormers and most rear extensions beyond the smallest, with design guidance on materials and dormer size. We build the heritage statement into the design stage.

Permitted development in Muswell Hill: what goes ahead without a planning application

Usually permitted development outside the conservation area. Haringey’s householder Article 4 directions cover only the Rookfield Estate, Noel Park, Peabody Cottages and Tower Gardens — none in Muswell Hill itself — but inside the Muswell Hill conservation area any roof addition and any rear extension over 3 m needs a planning application. On the streets outside it, lofts and single-storey rear extensions go ahead without one. Flats and maisonettes have no permitted development rights, whatever the street, and inside any conservation area a dormer or roof enlargement needs a planning application even where a single-storey rear extension within the limits does not.

On a house outside those streets, a rear dormer loft (40 m³ on a terrace, 50 m³ on a semi or detached house), a hip-to-gable, a single-storey rear extension of 3 m (4 m on a detached house) and a side-return infill are permitted development, and we apply for a Lawful Development Certificate on every one so the position is confirmed in writing. See our fixed-price permitted development projects — from £32,400 inc. VAT (£27,000 + VAT) for a Velux loft and £42,000 inc. VAT (£35,000 + VAT) for a 3 m rear extension, design and build inclusive, postcode dependent. Not sure whether your project needs a planning application? Planning check

Conservation areas and Article 4 directions in Muswell Hill

Two conservation areas cover most of N10. Muswell Hill (designated 1 March 1974) takes in the Edwardian centre and the avenues around it — the council’s appraisal describes it as “an essentially Edwardian suburb” built between 1896 and 1913 in red brick with stone and plaster detail. Rookfield (26 March 1976), the garden-estate enclave off Muswell Hill Road, is the only part of the area with an Article 4 direction: the 1978 direction is still in force and removes permitted development rights, so alterations there need a planning application. Muswell Hill itself has no Article 4 direction, which means front-facing changes still fall under normal permitted development, but any roof extension, side extension or rear extension deeper than 3 m needs planning permission because the house is in a conservation area. Streets outside both areas — towards Fortis Green, Alexandra Park and Colney Hatch Lane — usually proceed on a Lawful Development Certificate.

The rules Haringey applies

Haringey decides householder applications against its Development Management DPD (adopted 24 July 2017) rather than a borough-wide extensions guide — there is no borough-wide extensions SPD. Policies DM9 and DM12 require extensions in a conservation area to complement the style, scale and materials of the host house. The council’s own guidance expects extensions to be subordinate, accepts the larger-home-extension prior-approval route (up to 6 m on a semi or terrace, 8 m on a detached house) outside conservation areas, prefers rear dormers set in at least 1 m from gable edges and 0.5 m from hips, and refuses roof-shape changes that harm the streetscape. Inside any Haringey conservation area planning permission is needed for a single-storey rear extension deeper than 3 m, any two-storey rear or side extension, any roof addition or alteration, cladding, and rooflights or solar panels projecting more than 150 mm.

Basements fall under policy DM18 (Residential Basement Development and Light Wells), which requires structural stability to be demonstrated; the council charges a higher pre-application fee for properties with a basement. Haringey has no numerical 45-degree rule — daylight and outlook are judged under DM1 and the BRE guide — so we design to clear a 45-degree line from the nearest neighbouring habitable-room window as a matter of course, which keeps most schemes out of a daylight report.

Fees and timescales

A householder application costs £548 (from April 2026, plus the Planning Portal service charge) and Haringey has eight weeks from validation to decide it. Written pre-application advice for a householder scheme is currently listed at £312 (express) or £498 with a meeting; a general enquiry is £103. Party wall notices run alongside planning: two months’ notice for works to a shared wall, one month for excavations within 3 m or 6 m of a neighbour’s foundations.

Building control

Haringey runs its own building control service and is an LABC member. We use the council inspector on every project. Typical inspection points are commencement, foundation trenches, oversite and damp-proof course, drainage before backfill, structural steels and joists before they are covered, insulation and fire-stopping before plastering, then completion. We book each one and hand you the completion certificate at the end of the job.

Anderson's advice: start the party wall process early

Most clients underestimate the party wall timeline — it can add three months to a semi-detached or terraced project. We raise it at the first meeting so notices go out while the design is still being finalised, not after.

What our clients say

“We have used Lccl in the past for our rear house extension and have come back to instruct Lccl for our loft conversion too to our house in North London. As before we are very happy with the services from Lccl and we highly recommend their design and construction services for both home extension or loft conversion including both design and build services.”

— Mia M, Google Reviews

As LABC Building Excellence Award winners in 2024 (Best Residential Extension in London) and 2026 (Best Conversion or Alteration to an Existing Home, Weech Road NW6), every project is delivered by one team of architects, structural engineers, project managers and builders. Workmanship is guaranteed for 12 months from practical completion, with a 10-year LABC structural warranty.

Nearby areas

Muswell Hill is part of our North London guide. Nearby areas: Barnet, Finchley, Enfield, Edgware, Hendon, Highgate, Crouch End, Stoke Newington.

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

One team, one contract, one point of contact — from first sketch to handover.