House Extensions & Loft Conversions in Potters Bar

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

Potters Bar is 1930s and post-war semis and detached houses on good plots, a few minutes from our Hadley Wood new build and our Bohun Grove renovation. Hip-to-gable lofts, double-storey side extensions and wraparounds are typical.

What it costs in Potters Bar

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 Potters Bar

Lancaster Avenue, Hadley Wood EN4 — 3,033 sq ft luxury new build

A 3,033 sq ft detached house designed and built by our team from planning through to handover.

See the project

Also nearby: Vale Avenue, Borehamwood WD6 (hip-to-gable loft, 2021) · Bohun Grove, East Barnet EN4 (rear extension, hip-to-gable loft, renovation, outbuilding, landscaping, 2023).

Planning in Potters Bar

Hertsmere is pragmatic on permitted development and prior approval for larger extensions; Green Belt edges and The Royds conservation area need care on plot boundaries.

Permitted development in Potters Bar: what goes ahead without a planning application

Usually permitted development. The Royds is the one Potters Bar conservation area with a householder Article 4 direction (July 2015: dormers, rooflights, windows, paving and walls need permission); on the rest of the town, lofts and single-storey rear extensions go ahead without a planning application. Hertsmere applies a disproportionate-additions test in the Green Belt, which does not affect permitted development itself. 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 Potters Bar

Potters Bar’s conservation area is The Royds, designated in June 2000 — the distinctive 1930s estate by builder Edward Hicks with its peg-tile roofs and timber windows. An Article 4 direction confirmed in July 2015 removes permitted development there for box dormers and rooflights, replacement of the original timber windows, front-garden paving and removal of the crenellated boundary walls. The rest of EN6 — the late-Victorian streets south-east of the centre and the 1930s mock-Tudor semis of the town’s suburban growth — is outside any conservation area, so lofts and single-storey rear extensions normally proceed on a Lawful Development Certificate, with the larger 6 m or 8 m extension through prior approval. Houses on the Green Belt edge of the town are assessed under the disproportionate-additions test. Hertsmere also made an Article 4 direction on 23 April 2026 across the Parkfield, Oakmere, Furzefield and Bentley Heath & The Royds wards that will require planning permission to convert a house into a small HMO.

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: talk to your neighbours before the notices go out

Semi-detached hip-to-gable plus rear dormer combinations almost always fall under permitted development, but neighbours often object informally. A conversation over the fence before the party wall notice lands avoids most of it.

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

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

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.