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Design and build · London & Hertfordshire
Design and build London: one contract, one team, one point of contact — from first sketch to handover
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
Design and build means one company is responsible for the architecture, the structural engineering, the planning application, the building regulations, the party wall process and the construction — under one contract, with one project manager. It is how LCCL has delivered extensions, loft conversions, renovations, basements and new houses across London and Hertfordshire since 2004, and it is why the drawings are done by the people who will build from them. This page explains what design and build includes, what it costs for each project type in 2026, and how it compares with appointing an architect and a builder separately.
Quick answer
The same guide prices as each service page — from £32,400 inc. VAT (£27,000 + VAT) for a loft, £35,000 for an extension, £45,000 for a basement, £2,200 per m² for a new house — because design is included in every LCCL price, not added on.
Included. Lawful Development Certificate, prior approval or planning application as the project needs, prepared and submitted by our team.
Design and approvals 8–16 weeks; build 4 weeks to 14 months depending on the project.
A free 30-minute phone call with our team, no obligation.
Guide price
Design included in every range
Typical build
4 wks – 14 months
Guarantee
12-mo + structural · 10-yr LABC available
Awards
LABC 2024 & 2026 winners
LABC Building Excellence Award 2024
Best Residential Extension in London — Bohun Grove, East Barnet EN4: rear extension, hip-to-gable loft conversion and whole-house renovation
LABC Building Excellence Awards 2026
London Regional Winner, Best Conversion or Alteration — Weech Road, Hampstead NW6: penthouse loft conversion and full renovation
One contract
Architecture, structural engineering, planning, construction and project management — all under one contract
Guaranteed & insured
12-month workmanship guarantee; 10-year LABC structural warranty
What design and build with LCCL includes
Every stage under one contract. Nothing is subcontracted to you.
Free 30-minute consultation call and an instant estimate for your postcode
Measured survey of the house, roof and garden
Architectural design — concept, planning drawings and construction drawings — with revisions until you're happy
Planning: Lawful Development Certificate, prior approval or full application, prepared and submitted for you
Structural engineering: calculations and drawings by our chartered engineer, designed for the build not just the approval
Building regulations through LABC — full-plans drawings, inspections and the completion certificate
Party wall notices served on your behalf (£300 each, at cost); surveyor process managed where a neighbour dissents
A detailed itemised estimate — design, planning, structure, construction and warranty priced line by line — then a fixed contract sum
Construction by our own project-managed teams, one point of contact throughout, weekly progress updates
Kitchens, bathrooms and finishes fitted to your specification
12-month workmanship guarantee; 10-year LABC structural warranty
Handover pack: certificates, guarantees, drawings and the documents you need to sell
What does design and build cost in London in 2026?
Design, engineering and approvals are inside every LCCL price. These are the same ranges as the service pages.
Project
Design and build inclusive
Detail page
House extension — rear, side return, wraparound, kitchen, two storey
£42,000 – £198,000 inc. VAT (£35,000 – £165,000 + VAT)
Loft conversion — Velux, dormer, L-shaped, hip-to-gable, mansard
£32,400 – £148,800 inc. VAT (£27,000 – £124,000 + VAT)
Home renovation — single room to whole house
£18,000 – £180,000 inc. VAT (£15,000 – £150,000 + VAT)+
Basement — refit, lowering, new dig
£54,000 – £360,000 inc. VAT (£45,000 – £300,000 + VAT)+
New build house
£2,200 – £4,500 per m² (zero-rated for VAT), from £250,000 (zero-rated for VAT)
Standalone services
Guide
Notes
Architectural design and planning drawings only
From £750
Architecture — for clients who want drawings without the build
Why the price is inclusive: an architect's fee for a domestic extension is typically a percentage of the build cost, a structural engineer's fee is on top, and the builder prices the drawings he is given. Design and build folds all three into one contract sum, priced line by line in your itemised estimate, so you know the whole cost before you commit and there is no gap between the drawings and the price. The figure on your itemised estimate is the figure you pay — nothing is added afterwards. Postcode dependent — the instant estimator adjusts the range for your area in thirty seconds, and a detailed itemised estimate follows one survey.
What changes between the routes: with separate appointments, the architect designs, the engineer calculates, the builder tenders, and each hands the problem to the next — a drawing the builder cannot price, a steel the architect did not allow for, a planning condition nobody owns. With design and build, one team owns the drawing, the calculation, the price and the wall. Inner London (Camden, Islington, Hackney, Wandsworth, Hammersmith and similar) add 10–15%. Central London (Westminster, Kensington & Chelsea, the City) add 20–25%. Hertfordshire is about 5% less. These are estimated ranges — every home is surveyed and costed individually.
Design and build vs the alternatives
Design and build (LCCL)
One contract, one team, one point of contact. The drawings are done by the people who build from them, the structure is designed for the site, the price is fixed from the itemised estimate and the programme is one programme. Best for: almost every domestic extension, loft, renovation, basement and new house.
Architect + separate builder
You appoint an architect (typically a percentage of build cost), an engineer, and tender the drawings to builders. More design independence; more fees, more time, and the gaps between the three are yours to manage. Best for: unusual or highly bespoke architecture where the design is the point.
Builder only, no drawings
Cheapest on paper, and the source of most of the problems we are asked to fix — no building-regulations drawings, no structural calculations, no lawful development certificate to show a buyer. Not a route we recommend for anything structural.
Planning
How planning works under design and build
The application is part of the contract, not a separate fee — and it is designed for from the first sketch.
Route
Applies to
Time
What we do
1. Permitted development
Most lofts; single-storey rear to 3 m (4 m detached); side returns
No application
Lawful Development Certificate, ~8 weeks, included
2. Prior approval
Single-storey rear to 6 m (8 m detached)
42 days
Larger home extension submission with neighbour notification
3. Full planning
Wraparounds, two storey, mansards, basements, new builds, flats, conservation areas
8–13 weeks
Drawings, design statement, pre-app where worthwhile, application and negotiation
4. Listed building consent
Listed houses
8 weeks
Heritage statement alongside the application
Building regulations, party walls & warranty
The approvals inside every contract
Every project goes through building control with LABC — full-plans drawings and our own structural calculations, so the inspector is checking a design he has already approved. We are an LABC Registered Partner and our Bohun Grove EN4 and Weech Road NW6 projects won LABC Building Excellence Awards in 2024 and 2026.
Where the Party Wall Act applies we serve the notices at design stage and manage the surveyor process. Every project carries a 12-month workmanship guarantee; a 10-year LABC structural warranty.
Because the same team designs and builds, the planning drawings are already buildable — there is no second design stage after approval where the price changes. We check your address for permitted development rights, conservation areas and Article 4 directions before the first drawing.
House extension planning permission · How long planning takes
Recent design and build projects
Bohun Grove, East Barnet EN4 — rear extension, hip-to-gable loft and whole-house renovation
LABC 2024 Best Residential Extension in London
Semi-detached family home One programme loft + extension + renovation
A total renovation of a family semi: a rear extension opening into a full-width kitchen and dining space with floor-to-ceiling glazing and skylights, a hip-to-gable loft conversion with a rear dormer, two Lusso Stone bathrooms, enlarged bedrooms, new windows throughout, a regulated outbuilding and landscaping.
Because the loft and extension ran under one contract, the steelwork for the open-plan ground floor and the loft floor was designed together and lifted in on the same day — one crane hire, one scaffold, one building-control file.
See the Bohun Grove project · All projects
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ANDERSON · FOUNDER, LCCL CONSTRUCTION
Anderson's advice: book the design stage in summer, build in autumn
August is our slowest month for project starts — most families delay until the schools go back. That makes it the best time to get the survey, drawings and approvals done: you go through the council queue while everyone else is on holiday and start on site in September or October with the paperwork finished.
Approvals are the part of the programme you cannot compress. Design and planning typically take 8–16 weeks; leave them to the last minute and the build slips into the following year.
How design and build runs with LCCL
The same five stages on every project, from a Velux loft to a new house — only the durations change.
WEEK 0
Free consultation call
A 30-minute phone call with our team about the house, what you want and a realistic budget. Your instant estimate is the starting point. No video, no pressure.
WEEKS 1–4
Survey & design
Measured survey, architectural drawings and your detailed itemised estimate — design, planning, structure, construction and warranty priced line by line. Revisions until you're happy, then a fixed contract sum.
WEEKS 4–12
Approvals
Lawful Development Certificate or planning application, building-regulations drawings, structural calculations, party wall notices — all by our team. Nothing starts on site until it is signed off.
BUILD
On site
4 weeks for a Velux loft to 14 months for a new house. One project manager, one programme, weekly updates, and the people who drew it building it.
HANDOVER
Sign-off
Snagging, LABC final inspection and completion certificate, guarantees in writing, the handover pack. One team, one contract, one point of contact — from first sketch to handover.
“We are very happy with the services from Lccl, Alex has done a great job on design and construction. 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…”
Mia M · Google Reviews
“Everyone at LCCL Construction was skilled, trustworthy and worked to the highest standard. I am delighted with our loft conversion, it is exactly what we wanted and I highly recommend the company - they have transformed the quality of my home. Overall it…”
KashImaging · Google Reviews
“We are very pleased to have used Lccl Construction to do full house renovation and loft conversion to our edwardian terraced house. Project involved total strip out of interiors and remodelling repositioning the interior walls, electrical and plumbing…”
neil smith · Trustpilot
Design and build questions we get asked most
One company is responsible for the architecture, structural engineering, planning application, building regulations, party wall process and the construction, under one contract with one project manager. You are not the coordinator between an architect, an engineer and a builder — we are.
Usually not, and often less. An architect's fee for a domestic project is typically a percentage of the build cost, the engineer is on top, and the builder prices whatever drawings he is given. Design and build folds all three into one contract sum priced line by line, and the drawings are done by the people who build from them, so the price does not change after approval.
Not with a company whose work wins design awards. Bohun Grove EN4 won the LABC Building Excellence Award 2024 for Best Residential Extension in London and Weech Road NW6 the 2026 award for Best Conversion or Alteration — both design and build, drawings to handover. What you lose is the gap between the drawing and the build.
Yes. We can build from your architect's planning drawings, taking the project from technical design through construction under one contract, or provide structural calculations and project management as separate services. Most clients find one contract simpler.
Yes — every guide range on this site includes the survey, drawings, planning or lawful development certificate, building-regulations drawings, structural calculations, the build to plaster finish with first-fix services, LABC sign-off and guarantees. On top are the items you choose: kitchen units and appliances, sanitaryware above the allowance, flooring and second-fix finishes. The figure on your itemised estimate is the figure you pay — nothing is added afterwards.
After the survey you receive a document that prices every line of the project — design, planning, structure, construction, finishes and warranty — so you can see where the money goes and adjust the specification before you commit. It becomes the fixed contract sum. We never quote a single lump figure from a phone call.
Architects, structural engineers and project managers working under LCCL's contract, with our site teams — Anderson has run the company since 2004. Where a specialist is needed — a party wall surveyor for a neighbour, a basement waterproofing designer — we appoint and manage them within the contract.
A 12-month workmanship guarantee on every project, with a 10-year LABC structural warranty. Building control sign-off is through LABC on every job and you receive the completion certificate and all electrical and gas certificates at handover.
Where we design and build
From Finchley N3 we cover North London, North-West London, Central London, South-West and West London, and Hertfordshire — and we also work across the rest of London, Buckinghamshire, Surrey, Kent and Essex. Recent projects: East Barnet EN4, Hampstead NW6, Hadley Wood EN4, Mill Hill NW7, Chelsea SW10, Marylebone W1 and Fulham SW6.