House Extensions & Loft Conversions Muswell Hill N10 2026: Costs, Planning and What Suits an Edwardian House

By Anderson & the LCCL Construction Team | Finchley N3

Muswell Hill was built almost in one go in the Edwardian years, and it shows: wide semi-detached houses with big hipped roofs, deep gardens and a side passage, with Victorian terraces running down towards Hornsey and Crouch End. Both are good houses to add to. The semis take a hip-to-gable loft and a wraparound extension better than almost anything else in North London; the terraces suit a rear dormer and a side-return. We are based in Finchley N3, ten minutes away, and have built extensions and lofts across N10 for years.

This guide is the 2026 version: current ranges for each extension and loft type, how the London Borough of Haringey and the Muswell Hill conservation area change the planning picture, and what we would choose for each kind of house.

One of our house extension projects in Muswell Hill N10 — the Edwardian semis here take a rear or wraparound extension well.

Which extension suits a Muswell Hill house

• Edwardian semi-detached (the streets off the Broadway, Fortis Green, Alexandra Park Road): a wraparound — side return plus rear — gives the large open-plan kitchen and dining space these houses were never built with. A double-storey rear extension adds a bedroom and bathroom above it.

• Victorian terrace (towards Hornsey and Crouch End): a side-return infill beside the outrigger, or a full rear extension across the back, with a rear dormer in the roof.

• Both: an extension and a loft designed together nearly always cost less and disrupt less than two separate projects a few years apart.

House extension costs in Muswell Hill N10 (2026)

N10 sits in our base price band, so these ranges apply directly. They are inc. VAT with the ex-VAT figure in brackets and cover a shell-and-plaster finish; decorated and fully finished levels, kitchens, structural openings into the existing house and fees are separate lines.

• Rear extension (15–25 m²): £42,000 – £90,000 (£35,000 – £75,000 + VAT); a typical 20 m² rear extension is £46,000 – £62,000 inc. VAT.

• Side-return extension (12–20 m²): £42,000 – £93,600 (£35,000 – £78,000 + VAT).

• Wraparound (25–40 m²): £72,000 – £153,600 (£60,000 – £128,000 + VAT).

• Double-storey rear extension (30–50 m²): £90,000 – £198,000 (£75,000 – £165,000 + VAT).

Loft conversion costs in Muswell Hill N10 (2026)

• Velux / rooflight loft: £32,400 – £50,400 (£27,000 – £42,000 + VAT).

• Rear dormer: £56,400 – £80,400 (£47,000 – £67,000 + VAT).

• L-shaped dormer on a terrace with an outrigger: £58,800 – £98,400 (£49,000 – £82,000 + VAT).

• Hip-to-gable with rear dormer — the Edwardian semi's natural loft: £60,000 – £114,000 (£50,000 – £95,000 + VAT).

• Mansard: £76,800 – £148,800 (£64,000 – £124,000 + VAT).

Our instant estimate prices your own combination for N10 in about two minutes. For the thinking behind each loft type see dormer vs hip-to-gable vs mansard, and for extensions the rear extension cost guide.

The same Muswell Hill N10 project from the side — the side passage on an Edwardian semi is where a wraparound extension earns its keep.

Planning in Muswell Hill: Haringey and the conservation area

Muswell Hill is in the London Borough of Haringey, and a large part of the Edwardian centre sits inside the Muswell Hill Conservation Area. Inside it, the permitted development rights that would normally let you build a single-storey rear extension or a rear dormer without an application are cut back: side extensions and rear dormers need planning permission, roof alterations facing the street are scrutinised closely, and materials are expected to match the original brick, tile and timber. Outside the conservation area the national permitted development rules apply — a 3 m rear extension on a semi or terrace (6 m with prior approval), and a loft of up to 50 m³ on a semi or 40 m³ on a terrace under the loft rules, with the dormer set back from the eaves.

Hip-to-gable conversions on a semi are permitted development outside the conservation area, but Haringey will look at the change to the roof form if an application is needed. Our guides to loft conversion planning permission and permitted development for extensions cover the detail; our Crouch End N8 and Hornsey and Highgate N6 guides cover the neighbouring streets under the same council.

Anderson's advice

“Most clients underestimate the party wall timeline — it can add 3 months to a semi-detached project.” In Muswell Hill nearly every house shares at least one wall, and a wraparound plus hip-to-gable touches the party wall at the foundations, the first floor and the roof at once, so both neighbours get a notice. Serve the notices while the drawings are being finished, not when the scaffold is booked: a neighbour who dissents and appoints a surveyor adds weeks, and that is fine as long as those weeks are not the ones you planned to be on site.

Why design & build for a Muswell Hill project

As LABC Building Excellence Award Winners 2024 for Best Residential Extension in London — and London Regional Winners again in 2026 for Best Conversion or Alteration to an Existing Home — we design and build extensions and lofts across N10 with the architectural design, structural engineering, Haringey planning and building control applications and construction under one contract. Every project carries a 12-month workmanship guarantee and a 10-year LABC structural warranty.

What our clients say

“I highly recommend LCCL Construction. They completed our loft conversion to a very high standard, and the quality of workmanship throughout was excellent. The team was professional, reliable, and completed everything within a very reasonable timeframe. They were also fairly priced, which made the whole experience even better. We’re really pleased with the finished result and would definitely use them again.”

— Alina A, Google Reviews

Frequently asked questions

Do I need planning permission for a loft conversion in Muswell Hill?

Outside the Muswell Hill Conservation Area, a rear dormer or hip-to-gable within the permitted development volume limits (50 m³ on a semi, 40 m³ on a terrace) does not need an application, though a Lawful Development Certificate is worth having. Inside the conservation area, dormers and roof alterations need planning permission from Haringey.

What is the best extension for an Edwardian semi in Muswell Hill?

A wraparound — side return plus rear — for a large open-plan kitchen and dining space, or a double-storey rear extension if you need a bedroom and bathroom as well. Inside the conservation area the design has to respect the original house, which usually means matching brick and a lower, simpler rear elevation.

How much does a hip-to-gable loft cost in N10?

£60,000 – £114,000 inc. VAT (£50,000 – £95,000 + VAT) in 2026 for a hip-to-gable with rear dormer to a shell-and-plaster finish, before the bathroom fittings and a fully finished level.

Get a figure for your own project

To book a free 30-minute consultation call about your extension or loft conversion in Muswell Hill, call LCCL Construction on 020 8037 7332 or get an instant estimate online — six questions, about two minutes, and you see a real range for your postcode on screen. Finchley N3 based, covering all of London and Hertfordshire.

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