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
Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
Call 020 8037 7332 or get an instant estimate online.
Structural engineering · London & Hertfordshire
Structural engineer calculations: £450–£8,000, 1–3 weeks, accepted by building control
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
Every steel beam, every wall that comes out, every new floor in a loft and every underpinned basement needs structural calculations before building control will approve it — and before a builder can order the steel. LCCL provides them through our chartered structural engineer as part of every design and build contract, and as a standalone service for clients building with someone else. This page explains what the calculations cover, what they cost in 2026 by project type, how long they take and how they fit with building regulations.
Quick answer
£450–£8,000 as a standalone service depending on the project — a single beam at the bottom, a basement or new house at the top. Included at no separate fee in every LCCL design and build contract.
Calculations are for building regulations, not planning — but on a basement they are part of the planning application too.
1–3 weeks from receiving the drawings and survey to a full calculation package.
A free 30-minute phone call with our team, no obligation.
Guide price
£450 – £8,000
Typical time
1–3 weeks
Included in
Every design & build contract
Accepted by
LABC and all building control bodies
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 structural calculations from LCCL include
Available on its own, or included in every LCCL design and build contract.
Review of the architectural drawings and the measured survey; site visit where the existing structure needs to be seen
Design of every new structural element — steel beams, posts, padstones, lintels, new floor joists, roof structure, foundations
Calculations to the current Eurocodes, checked and signed off by a chartered structural engineer
Structural drawings: beam layout, sections, connection details and a steel schedule the fabricator can price from
Foundation design, including piled or deepened foundations near trees on clay
Temporary works advice — propping sequence for knock-throughs, underpinning sequence for basements
Submission to building control as part of the full-plans application; responses to the checking engineer's queries
Revisions where the design changes during construction, at an agreed rate
Coordination with our architectural drawings so the calculations and the drawings are one package
A PDF package you can hand to any builder or building control body
How much do structural calculations cost in London in 2026?
Guide fees by project type as a standalone service. Within a design and build contract, the calculations are inside the project price.
Project
What is designed
Guide fee
Single opening — one beam for a knock-through or a bi-fold door
One beam, padstones, any post; temporary works note
£450 – £900
Extension or loft conversion
Beams, new floor, roof structure, foundations, connections
£900 – £2,500
Whole-house renovation, two storey extension or wraparound
Multiple beams and floors, transfer structures, new foundations
£2,400 – £5,400 inc. VAT (£2,000 – £4,500 + VAT)
Basement or new build house
Underpinning sequence, retaining walls, slab, full superstructure, foundation design
£4,000 – £8,000 (zero-rated for VAT)
Related service
Guide
Notes
Party wall notices
£300 per notice at cost
Party wall surveyor — the calculations show what bears on the shared wall
What the fee includes: the design, the calculations, the structural drawings and the building control submission. Not included: a site investigation where ground conditions are unknown (trial pits or boreholes, quoted separately), and building control's own fee. The figure on your itemised estimate is the figure you pay — nothing is added afterwards. If you go on to build with LCCL, the engineering fee is absorbed into the project price.
What the calculations save you: the steel is the most under-budgeted item on a ground-floor knock-through — typically £4,000–£12,000 on a Victorian terrace. Designing it properly, early, from a measured survey means the right sections are ordered once, the fabricator prices from a schedule rather than a guess, and the beam arrives the week it is needed instead of holding the programme.
Structural calculations by project type
Knock-throughs and open-plan ground floors
The most common request: removing the wall between the kitchen and the dining room, or the back wall for bi-fold doors. One or two beams, padstones and a post — and the check that the wall above is properly supported while the beam goes in.
Extensions and lofts
The extension roof and any beam across the opening; for a loft, the new floor joists or steels spanning between party walls, the dormer or gable structure, and the stair opening. Designed together where both are built together.
Basements and new builds
The heavy end: underpinning in a numbered sequence, retaining walls, the slab, and on a new house the whole superstructure and foundations — with a site investigation first where the ground is unknown. On a basement the calculations feed the planning application's impact assessment.
Planning
Are structural calculations needed for planning?
No — they are for building regulations. The exception is a basement, where the engineering is part of the planning case.
Approval
Needs calculations?
When
What we do
Planning application or LDC
No (basements excepted)
—
Architectural drawings only
Building regulations — full plans
Yes, for every structural element
Before work starts
Calculations and structural drawings submitted with the full-plans application
Building regulations — building notice
Yes, requested by the inspector on site
Before the beam goes in
We recommend full plans instead — no surprises on site
Basement planning application
Yes — basement impact assessment
With the application
Structural method statement and underpinning sequence for the BIA
Building regulations & party walls
The other approvals
Whatever the planning position, every structural change, extension, loft or basement needs building-regulations approval. We work through LABC with full-plans drawings and our own structural calculations, so the inspector is checking a design he has already approved. Where a shared wall or a neighbour's foundations are affected, the Party Wall Act applies and notices go out at least two months before work starts.
Building control will not sign off a structural element without calculations, and a buyer's surveyor will ask for them when you sell. Full-plans approval — drawings and calculations checked before work starts — is the route we use on every LCCL project; a building notice leaves the checking to the inspector on site, which is where programmes slip.
Projects our engineer designed
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.
How structural calculations run with LCCL
From the drawings to building control approval. One to three weeks in most cases; longer where a site investigation is needed first.
DAY 0
Send us the drawings
Architectural drawings and the measured survey — ours or another architect's. A free call to agree the scope and the fee.
WEEK 1
Site visit & design
The existing structure inspected where it matters; every new element designed to the Eurocodes; temporary works considered.
WEEKS 1–3
Calculations & drawings
Full calculation package checked and signed by our chartered engineer; beam layout, sections, connection details and a steel schedule.
SUBMISSION
Building control
Calculations submitted with the full-plans application through LABC; the checking engineer's queries answered by us.
ON SITE
Support
Revisions where the design changes, at an agreed rate; the fabricator prices from our schedule and the inspector signs off against our drawings.
“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
“We did a 3x10m single storey rear extension with LCCL recently. It was scheduled to take 12 weeks to complete but with Alex's experience and agile project management, we are ahead of schedule (finished in 10). Alex, and LCCL,is extremely knowledgeable and…”
Galichet Christophe · Google Reviews
Structural calculation questions we get asked most
£450 to £8,000 in 2026 depending on the project: a single beam for a knock-through £450–£900, an extension or loft £900–£2,500, a whole-house renovation or two storey extension £2,400 – £5,400 inc. VAT (£2,000 – £4,500 + VAT), a basement or new house £4,800 – £9,600 inc. VAT (£4,000 – £8,000 + VAT). Within an LCCL design and build contract they are inside the project price.
One to three weeks from receiving the architectural drawings and survey. A site investigation, where the ground is unknown, adds two to four weeks before the design can start — common on basements and new builds.
Yes, if the wall carries anything — and most internal walls in a London house carry the floor above, the roof or both. Building control will not sign the work off without calculations, and a buyer's surveyor will ask for them when you sell.
Yes. They are prepared to the current Eurocodes and checked and signed by a chartered structural engineer, and we submit them through LABC on every LCCL project. Any building control body, local authority or approved inspector, accepts the same package.
Yes — the standalone service gives you a PDF package with calculations, structural drawings and a steel schedule to hand to any builder. If you later build with us, the fee is absorbed into the project price.
The concrete or engineering-brick block that spreads a beam's load into the wall below. An undersized or missing padstone is the most common structural defect we find on jobs done without calculations — the beam is fine, the brickwork under it is crushing.
Typically £4,800 – £19,200 inc. VAT (£4,000 – £16,000 + VAT) for the load-bearing opening on a Victorian terrace, depending on its width ground-floor knock-through, fabricated, delivered and installed — the most under-budgeted item on a renovation. Calculations done early mean the fabricator prices from a schedule and the beams are ordered once.
Yes, where the job needs it — a propping sequence for a knock-through with the floor above loaded, or the numbered underpinning sequence a basement dig depends on. On a basement this also feeds the planning application's impact assessment.
Where we provide structural calculations
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. Standalone calculations are a desk service with a site visit where the existing structure needs to be seen, so we cover the whole of London and Hertfordshire.