House Extensions & Loft Conversions in Borehamwood

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

Borehamwood and Elstree are post-war and 1960s houses with room to extend: rear and wraparound extensions, hip-to-gable and rear dormer lofts, and full renovations of the older stock around Elstree village.

What it costs in Borehamwood

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 Borehamwood

Vale Avenue, Borehamwood WD6 — hip-to-gable loft

A hip-to-gable loft conversion on a 1950s semi in Borehamwood: a new bedroom with en-suite, permitted development, six weeks on site.

See the project

Also nearby: Lancaster Avenue, Hadley Wood EN4 (new build, 2026) · Bohun Grove, East Barnet EN4 (rear extension, hip-to-gable loft, renovation, outbuilding, landscaping, 2023).

Planning in Borehamwood

Hertsmere; Elstree village is a conservation area, otherwise permitted development and prior approval (8m detached / 6m semi) cover most projects.

Permitted development in Borehamwood: what goes ahead without a planning application

Usually permitted development. Hertsmere has no householder Article 4 direction in Borehamwood or Elstree, so on the post-war and 1930s streets of WD6, lofts and single-storey rear extensions go ahead without a planning application. 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 Borehamwood

Borehamwood grew from a rural hamlet into a town of 1950s London-overspill housing, with the film studios a major factor in its growth, and it has no residential conservation area — Hertsmere’s only Article 4 direction nearby is on rural land at Theobald Street. That makes WD6 one of the most straightforward places we work: lofts and single-storey rear extensions on the post-war semis and terraces normally proceed on a Lawful Development Certificate, and the larger 6 m or 8 m rear extension goes through the 42-day prior-approval route. The exceptions are Elstree village, which is a conservation area where roof, side and two-storey rear extensions need planning permission, and the Green Belt edges towards Elstree, Well End and Shenley, where the disproportionate-additions test applies.

Extension size rules Hertsmere applies

Hertsmere decides householder applications under its Core Strategy (January 2013) and Site Allocations and Development Management Policies Plan (November 2016), with the detail in Part E of its Planning and Design Guide, “Guidelines for Residential Extensions and Alterations” (2006), which is still the active guidance. Single-storey rear extensions are limited to 3.35 m beyond the original rear wall (para 1.c), with eaves of 3 m on a flat roof or 4 m on a pitched roof (1.k–1.l). First-floor rear extensions are governed by a 45-degree line to the neighbour’s first-floor window (3.e–3.f). Side extensions should be no more than half the width of the main house (2.b, 4.c); a two-storey side extension is set back at least 1 m from the front wall (4.f) and kept 1 m from the boundary, or 2 m where the street has significant gaps between houses (2.e, 4.k, 4.m). Dormers go in the rear slope, take up no more than 60% of the roof face, sit 0.3 m from the ridge and eaves and 0.5 m from the boundaries (6.f, 6.l), and front dormers are resisted (6.g). A minimum garden of 60 m² is kept for a two- or three-bedroom house, 80 m² for four bedrooms and 100 m² for five or more (1.e). In the Green Belt, extensions must not be disproportionate to the original house, individually or cumulatively, and must stay subordinate to it.

Light to neighbours

Hertsmere writes the daylight test into Part E: an extension should not cross a 45-degree line taken from the nearest edge of a neighbour’s front or rear window (para 1.b). We design to the line from the first sketch.

Fees and timescales

A householder application costs £548 (from April 2026, plus the Planning Portal charge) and Hertsmere has eight weeks to decide it. On the council’s April 2024 schedule, householder pre-application advice was £192 including VAT for a written response or £312 with a meeting, answered within 25 working days. 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

Hertsmere’s building control is delivered by Hertfordshire Building Control Ltd, the company owned by seven Hertfordshire councils including Hertsmere and an LABC member. We use it on every project and book each inspection from foundations to completion, handing you the completion certificate at the end of the job.

Anderson's advice: book your start date around the school year

August is our slowest month for project starts — most families delay until schools go back. If you can start in August you often get an earlier slot and a quieter street for scaffolding.

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

Borehamwood is part of our Hertfordshire guide. Nearby areas: St Albans, Watford, Potters Bar.

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.