House Extensions & Loft Conversions in Highgate

LCCL Construction is a design and build company based in Finchley N3, working in Highgate 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.

Highgate is Georgian and Victorian villas and terraces, many listed or in the Highgate conservation area. Lofts here are usually flush rooflights or carefully proportioned rear dormers; extensions are rear, glazed and sensitive to the garden elevation; full renovations of large houses are common.

What it costs in Highgate

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).

A recent LCCL project near Highgate

Weech Road, Hampstead NW6 — penthouse duplex loft conversion

A top-floor flat turned into a penthouse duplex: the kitchen and living space moved up into the new loft, two new bathrooms, an extra bedroom and views across to the Shard, the London Eye and Parliament. LABC Building Excellence Awards 2026 London Regional Winner — Best Conversion or Alteration to an Existing Home.

See the project

Planning in Highgate

Split between Haringey and Camden, both with strict conservation-area policies; listed buildings need Listed Building Consent. Pre-application advice and a heritage statement are standard on our Highgate projects.

Conservation areas on both sides of Highgate

Highgate is split down the High Street between two councils. The Haringey Highgate conservation area was designated on 21 December 1967 and covers the village core with its elegant red-brick terraces; the Camden Highgate conservation area (1968) covers the western slopes towards Hampstead Heath. Neither side has an Article 4 direction on houses, so front-facing replacement windows stay permitted development, but in both areas any roof extension, side extension or single-storey rear extension deeper than 3 m needs planning permission, Camden judges rear extensions on whether they stay subordinate to the house, and listed buildings need Listed Building Consent.

Haringey side (N6 east of the High Street)

Haringey has no extensions SPD; policies DM9 and DM12 of its 2017 Development Management DPD require conservation-area extensions to complement the host house, rear dormers are expected to sit at least 1 m in from gable edges and 0.5 m from hips, and basements are decided under policy DM18 with structural stability demonstrated. Daylight is judged under DM1 and the BRE guide. Written householder pre-application advice is currently £312, or £498 with a meeting.

Camden side (N6 west of the High Street)

Camden applies its Home Improvements guidance (January 2021): subordinate extensions, single-storey side extensions, dormers subordinate to the roof slope, and the 45-degree and 25-degree BRE daylight tests. Every basement needs planning permission under the borough-wide Article 4 direction in force since 1 June 2017, limited to one storey, half of each garden and 1.5 times the house footprint, with an audited Basement Impact Assessment. Homeowner pre-application advice is £481.50 or £963 including VAT.

Fees, timescales and building control

Either council charges £548 for a householder application (from April 2026, plus the Planning Portal charge) and has eight weeks to decide it. 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. Both boroughs run their own building control; we use whichever council the house falls in and book every inspection from foundations to completion.

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

“The Lccl construction team built my extension with a quick and clean service, they worked non stop through the winter weather.. I would highly recommend this company!”

— Chris Dunn, 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

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