Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
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Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
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Building regulations · London & Hertfordshire
Building regulations for extensions and loft conversions: what is checked, and how LCCL gets you the certificate
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
Every extension and every loft conversion needs building regulations approval, whether or not it needs planning permission. It is the check that the structure, fire safety, insulation, drainage and glazing are right — and the completion certificate at the end is the document your buyer's solicitor will ask for. This page explains what is inspected, the two ways to apply, how we do it through LABC, and what the Party Wall Act adds on a terrace or semi.
Quick answer
Building-control charges are set by each council and paid at cost; our full-plans drawings, structural calculations, inspections and completion certificate are included in the design and build price.
Building regulations apply to every extension, loft, basement and structural alteration — separately from planning. We use the full-plans route with LABC so the design is approved before we start.
Full-plans approval typically 5–8 weeks, running alongside planning; inspections at each stage of the build; completion certificate at handover.
A free 30-minute phone call with our team, no obligation.
Applies to
Every extension, loft, basement, structural change
Route we use
Full plans with LABC
Approval
5–8 weeks, alongside planning
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 building control checks on an extension or loft
The parts of the Building Regulations that apply to almost every project, and what the inspector looks at on site.
Part
What it covers
What is inspected
A — Structure
Foundations, steels, floor joists, the new roof
Trench depth before concrete; steels, padstones and bearings before they are covered
B — Fire
Escape windows, fire doors, a protected stair on a loft, detectors
Door specifications, window sizes, alarm positions at first and second fix
C and H — Damp and drainage
Damp-proofing, ground floor, new drains and the connection to the sewer
Drains laid and tested before backfill; a Thames Water build-over agreement where the extension sits over a public sewer
L — Energy
Insulation in floor, walls and roof; the glazed area of an extension; boiler and controls
Insulation before plaster; window energy ratings
F, G, P — Ventilation, water, electrics
Extract fans, hot water, new circuits
Certificates from the electrician and plumber
K and M — Stairs and access
Loft stair pitch and headroom, guarding, level thresholds
Stair before it is boxed in
Route
How it works
When we use it
**Full plans**
Drawings and structural calculations submitted before work starts; approved in 5–8 weeks; the inspector checks a design already agreed
Every LCCL project
**Building notice**
Two days' notice, no drawings approved in advance; the inspector decides on site
Never — it moves the risk to the build and your money
**Regularisation**
Retrospective approval for work done without it
When a previous owner built without a certificate — we can often regularise as part of a new project
How building control runs on an LCCL project
From the structural design to the certificate you keep.
Stage
What happens
When
1. Structural design
Our chartered engineer designs the steels, foundations and floor from the measured survey
With the planning drawings
2. Full-plans submission
Building-regulations drawings and calculations to LABC
Alongside planning
3. Approval
LABC checks the design and issues full-plans approval
5–8 weeks
4. Party wall
Notices 2 months before works to a shared wall (steels, chimney, party wall build), 1 month for excavation within 3 m / 6 m
Before we start
5. Site inspections
Foundations, drains, steels, damp course, insulation, fire, stairs — booked by us at each stage
Through the build
6. Completion certificate
Final inspection, certificate issued to you; 10-year LABC structural warranty
Handover
Why full plans and not a building notice: with full plans the inspector is checking a design he has already approved, so there are no surprises at first fix and no argument about a steel size when the scaffold is up. A building notice is lower-cost for a builder to start with and more expensive for you to finish — every decision is made on site under time pressure. We are an LABC Registered Partner and our Weech Road NW6 and Bohun Grove EN4 projects won LABC Building Excellence Awards in 2026 and 2024.
Party walls: on a terrace or semi the Party Wall etc. Act 1996 applies whenever we cut into, build on or excavate near a shared wall — steels bearing on it, a chimney breast coming out, a side return built up to the line, foundations within 3 m. Notices go out at least 2 months before (1 month for excavation); most neighbours consent; where one dissents a surveyor is appointed and we manage it (from £750 per neighbour). Notices £300 each at cost. See party wall notices and surveyors.
What LCCL includes for building regulations
Design and build inclusive — the engineer, the drawings, the inspections and the certificate are in the price.
Structural calculations by our chartered engineer, from the measured survey
Building-regulations drawings — full plans, not a building notice
Submission to LABC and the approval, before anything starts on site
Party wall notices served on your behalf (£300 each, at cost)
Thames Water build-over agreement where an extension sits over a public sewer
Every site inspection booked and attended by your project manager
Electrical and gas certificates from our registered engineers
LABC completion certificate handed to you at the end
12-month workmanship guarantee; 10-year LABC structural warranty
Projects signed off by LABC
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: budget for the steelwork, not just the kitchen
Clients budget for kitchen units but forget the structural steelwork when opening up ground-floor walls. On a Victorian terrace that is typically £4,800 – £19,200 inc. VAT (£4,000 – £16,000 + VAT) for the load-bearing opening, depending on its width — we price it on every proposal so there is no surprise.
Get the structural design done early, from a measured survey, and the steel arrives on site the week it is needed rather than holding the programme.
“Contracted lccl construction to design and build hip to gable loft conversion, after much research I found Lccl construction to be the most efficient and reliable company to deal with, the initial design phases started immediately their architects attended…”
Behar · Trustpilot
“2ND project with LCCL construction wraparound house extension. Completed full design and build process to our home in Finchley north London. Previously they have design and build our loft conversion 4 years on and still it is in excellent condition.…”
Anthony · Trustpilot
“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
Building regulations questions we get asked most
Yes. Planning and building regulations are separate: permitted development removes the need for planning permission, never the need for building regulations. Every extension, loft conversion, basement and structural alteration needs building-control approval and a completion certificate.
Full plans means the drawings and structural calculations are checked and approved before work starts; a building notice means you tell the council two days before and the inspector decides on site. We only use full plans — the design is agreed, the steel sizes are known, and there are no surprises at first fix.
Local Authority Building Control — the councils' own building-control service. We are an LABC Registered Partner: the inspector checks our drawings before the job and visits at every stage. Our Weech Road NW6 loft won the LABC Building Excellence Award 2026 (London) and Bohun Grove EN4 won in 2024.
The document LABC issues after the final inspection confirming the work complies. It is what your buyer's solicitor, your lender and your insurer will ask for. We hand it to you at handover with the guarantees.
It can usually be regularised: building control inspects the existing work, sometimes with opening-up, and issues a regularisation certificate. We can do this as part of a new project. Selling without it means indemnity insurance and a nervous buyer.
On a terrace or semi, whenever the work cuts into, builds on or excavates near a shared wall — which is nearly every extension and loft. Notices 2 months before (1 month for excavation); most neighbours consent; a surveyor only if one dissents. We serve the notices and manage the process.
A 12-month workmanship guarantee on every project, with a 10-year LABC structural warranty. Building control sign-off is through LABC — we are an LABC Registered Partner and LABC Building Excellence Award winners in 2024 and 2026.
Two steps. The instant estimator gives you a range for your postcode and project in thirty seconds. Then one measured survey gives you a detailed itemised estimate — design, planning, structure, construction and warranty priced line by line — with no obligation.
Where we 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 extensions: East Barnet EN4, Finchley N3, Putney SW15, Mill Hill NW7, Wood Green N22 and Borehamwood WD6.