House Extensions & Loft Conversions in Chiswick

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

Chiswick's Victorian and Edwardian terraces — Grove Park, Bedford Park, the Glebe Estate — are kitchen-extension and rear-dormer territory, with the Bedford Park conservation area setting a high bar on detailing.

What it costs in Chiswick

Inner London — typically +10–15% on base prices. 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: £29,500–£48,500
• Rear dormer loft: £51,500–£77,000
• L-shaped dormer: £54,000–£94,500
• Hip to gable: £55,000–£109,000
• Mansard: £70,500–£142,500
• Rear extension: £38,500–£86,000
• Side return: £38,500–£89,500
• Wraparound: £66,000–£147,000
• Double storey: £82,500–£189,500

Kitchen fit-out on top of the structure: +£15,000–£75,000. Basements: cellar refit £45k–£95k, lowering £95k–£180k, new dig £180k–£300k+. New build: £2,200–£4,500 per sqm.

A recent LCCL project near Chiswick

Guardhouse Way, Millbrook Park, Mill Hill NW7 — kitchen extension

A large modern kitchen and dining space for a family home, with a separate utility room so the kitchen stays quieter and gains cupboard space.

See the project

Planning in Chiswick

Hounslow; Bedford Park, Strand-on-the-Green and Grove Park conservation areas need planning permission for most external changes; elsewhere permitted development covers lofts and single-storey rear extensions. Two party wall awards per terrace.

Conservation areas and Article 4 directions in Chiswick

Chiswick has eight conservation areas. Bedford Park (designated 16 April 1970) is the pioneering 1875–86 Queen Anne Revival suburb by Norman Shaw and others — the council’s appraisal calls it the first place where the relaxed, informal mood of a village was adopted for a complete speculative suburb — and it has had an Article 4 direction on its unlisted houses since 24 July 2001 covering the design and fabric of the buildings, their curtilages and street frontages. Turnham Green (4 September 1975, extended 2001 and 2020) takes in the Devonhurst streets with their half-timbered gables, classical porches and art nouveau glass. Strand on the Green, Old Chiswick, Chiswick High Road, Grove Park, Wellesley Road and Chiswick House make up the rest. Householder Article 4 directions in Hounslow apply only in Bedford Park and Gunnersbury Park, so elsewhere front-facing replacement windows remain permitted development while roof extensions, side extensions and two-storey rear extensions in a conservation area need planning permission (a single-storey rear extension within the national 3 m or 4 m limit is still permitted development). A borough-wide Article 4 direction has required planning permission for small HMO conversions since 4 September 2023. The W4 terraces outside the conservation areas take lofts and rear extensions on a Lawful Development Certificate.

Extension size rules Hounslow applies (Residential Extension Guidelines, December 2017)

Hounslow’s Residential Extension Guidelines SPD (adopted December 2017 under the 2015 Local Plan) still uses imperial-derived depths: single-storey rear extensions of 3.05 m on a terrace, 3.65 m on a semi and 4.25 m on a detached house, kept below first-floor windows (para 4.3); two-storey rear extensions no more than half the width, 2.5 m deep and 2 m from the neighbour’s side wall (4.6); single-storey side extensions set back 1 m from the front and below the first-floor eaves (4.4); two-storey side extensions set back 1 m, under half the width and with a ridge at least 0.5 m lower (4.5); rear dormers at least 0.3 m below the ridge, 0.5 m above the eaves and 0.5 m from the sides, or 1 m on larger houses (4.10). In conservation areas rear dormers must be under half the roof width, 1 m down from the ridge and 1 m above the eaves, and front dormers and hip-to-gable conversions will not normally be accepted (6.2); the garden retained must at least equal the footprint of the original house (3.6). Basements (4.7) are a single subterranean floor extending into the garden no further than the rear-extension depths above, with at least 1 m of soil cover and lightwells within 1 m of the front wall or 2 m of the rear; in the functional flood plain (zone 3b) no basements or extensions are acceptable (3.9). The guidelines set no numerical daylight rule; 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. Hounslow’s 2026/27 pre-application fees are £408.44 for a written householder response, £558.55 with a meeting, £769.87 with a site visit or £1,232.82 for a listed building, with follow-ups at 75% within six months. The Local Plan Review 2020–2041 is at examination and programmed for adoption in 2026. 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

Hounslow runs its own building control service. We use the council inspector on every project. Typical inspection points are commencement, foundation trenches, oversite and damp-proof course, drainage before backfill, structural steels and joists before they are covered, insulation and fire-stopping before plastering, then completion. We book each one and hand you the completion certificate at the end of the job.

Anderson's advice: put the rooflights over the island

Rooflights over kitchen islands transform natural light more than any other single design decision. We position them on the plan before the kitchen layout is fixed, 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 Warranty available to purchase.

Nearby areas

Chiswick is part of our West London guide. Nearby areas: Ealing.

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.