House Extensions & Loft Conversions in St Albans

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

St Albans, Harpenden and the villages around them have detached and semi-detached houses on generous plots: wraparound and double-storey extensions, hip-to-gable lofts and new-build plots are the work here.

What it costs in St Albans

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 St Albans

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

Planning in St Albans

St Albans is a conservation-area city centre with Green Belt around the villages; outside those, permitted development and prior approval (8m detached / 6m semi) cover most extensions. New builds go through full planning with design-code and Green Belt policy checks.

Conservation areas and Article 4 directions in St Albans

The St Albans conservation area was designated in 1969 and extended in 1980, 1981, 1991 and 1996; it is divided into 23 character areas running from Roman Verulamium through the Abbey and medieval core to the Georgian streets around Fishpool Street, the Victorian railway quarter and the Victorian and Edwardian suburbs. Inside it, roof, side and two-storey rear extensions need planning permission, and in the Article 4 direction areas — Verulam and Fishpool Street, Sopwell Lane and Albert Street, Cunningham Avenue and Childwickbury — the council’s own words are that “most of your permitted development rights will have been removed”, so expect a planning application for almost any external change. Outside the conservation area, the AL1–AL4 suburbs of Marshalswick, Fleetville, Bernards Heath, Chiswell Green and London Colney take lofts and rear extensions on a Lawful Development Certificate, with the larger 6 m or 8 m extension through prior approval.

Green Belt and the rules St Albans applies

St Albans still decides applications under its 1994 District Local Plan while the new Local Plan completes examination (the main modifications consultation opened on 13 April 2026 and the council gives the emerging plan significant weight). The Green Belt around the villages is where the district differs most from London: the council’s supplementary guidance on residential extensions and replacement dwellings in the Green Belt (adopted 26 May 2004) treats an increase of 20–40% in floorspace, or 90–180 m³ in volume, over the original house as the guideline range for a proportionate extension — expressly guidelines rather than rigid limits, measured against the house as built or as it stood on 1 July 1948. Outside the Green Belt the district applies the national permitted-development volumes (40 m³ on a terrace, 50 m³ on a semi or detached house for lofts) and judges extensions on design and neighbour amenity; we design to the 45-degree line as standard.

Fees and timescales

A householder application costs £548 (from April 2026, plus the Planning Portal charge) with an eight-week decision period. St Albans offers written pre-application advice only (no meetings), aiming to reply within six weeks; on its April 2024 schedule that was £208.80 including VAT for a householder extension and £306 for a listed building or conservation-area scheme. 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

St Albans and Watford run a shared building control service. We use the council inspector 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

“Super professional and on the ball at all times. All his teams are excellent and hard working. They are conscientious and want the job to be well done.”

— Ludovic, Reviews.io

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

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