House Extensions & Loft Conversions across South East London

LCCL Construction is a design and build company based in Finchley N3, working across South East London 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.

South East London stock is mixed: Victorian terraces in Peckham, Brockley and Forest Hill, 1930s semis further out in Bromley and Eltham. That mix means side returns and rear dormers nearer the centre, and hip-to-gable lofts and wraparound extensions in the suburbs.

What it costs across South East London

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 South East London

Glendarvon Street, Putney SW15 — rear extension

A rear extension to a Victorian terrace in Putney: an open-plan kitchen-diner with skylights and bifold doors onto a landscaped garden, plus a new WC and pantry tucked into the old footprint.

See the project

Also nearby: Tetcott Road, Chelsea SW10 (wraparound extension, renovation, 2025) · Chipstead Street, Fulham SW6 (basement, loft conversion, rear extension, renovation, 2024).

Planning across South East London

Southwark and Lewisham run standard householder routes with some conservation areas (Telegraph Hill, Blackheath); Bromley and Greenwich are generally permissive under permitted development. Blackheath and Greenwich have listed and conservation stock needing more care.

Permitted development in South East London: what goes ahead without a planning application

Usually permitted development. Southwark’s householder directions cover the Sunray Estate and a few sites; Lewisham’s sit in its 26 conservation areas (Blackheath, Brockley, Telegraph Hill, Forest Hill); Greenwich’s include the Ashburnham Triangle; Bromley removed roof rights in Petts Wood and Chislehurst Road in 2022. On the ordinary streets, 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

Borough by borough

Lewisham is the most prescriptive of the four: its Alterations and Extensions SPD (April 2019, under the Local Plan adopted 16 July 2025) limits rear extensions to about 3 m and half the garden depth, keeps two-storey side extensions 1 m from the boundary, allows basements of one storey no more than 3 m beyond the rear wall or a quarter of the garden with 2.4 m headroom, and applies 45-degree and 25-degree guides; 26 conservation areas from Blackheath to Telegraph Hill carry Article 4 directions and a borough-wide small-HMO direction has applied since January 2024. Southwark adopted a new Householder Development SPD on 7 July 2025 that is deliberately qualitative — extensions must stay subservient to the house and are judged case by case under the Southwark Plan 2022 — with 48 conservation areas including Dulwich Village and Camberwell Grove and an Article 4 direction on the Sunray Estate. Greenwich works to its 2014 Core Strategy and its Residential Extensions, Basements and Conversions guidance, which standardises rear extensions at 3–3.6 m on terraces and semis and 4 m on detached houses, no more than half the garden, with basements limited to one level within the house footprint and none in Flood Zone 3; Ashburnham Triangle has had an Article 4 direction since 2014. Bromley (Local Plan January 2019) has no extensions SPD; its hard rule is Policy 8’s 1 m side space for anything two storeys or higher, and it has removed roof-extension rights in the Petts Wood area of special residential character and Chislehurst Road (from 19 July 2022) and small-HMO rights borough-wide from September 2022. Written householder pre-application advice ranges from £250 (Bromley) to £317 (Southwark). All four run their own building control.

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

“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.

Areas we cover

We work across Blackheath, Greenwich, Dulwich, Peckham, Brockley, Forest Hill, Lewisham, Sydenham, Bromley, Beckenham and Eltham — the same team, the same contract and the same price bands apply, and we survey every project in person before quoting.

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.