Structural Works London
Steel beams, load-bearing walls, underpinning, bay rebuilds and new steel frames for London houses, built to a structural engineer's design.
Structural Work Done in the Right Order
At a glance: Alstruct carries out structural building work in London homes: removing load-bearing walls and fitting steel beams, underpinning foundations, rebuilding failing bays, replacing lower floors with a new steel frame and footings, and lowering floors for more headroom. A structural engineer designs the work, we hold the house on temporary supports while it is done, and Building Control inspects it. The company is led by an engineer, and every job carries our 10-year workmanship warranty.
Structural work is the part of a building job that nobody sees once it is finished, and the part that matters most. Before a wall comes out or a bay comes down, the structure above has to be held on props and Strongboys, and the beam, posts and padstones that replace it have to be sized by a structural engineer. We arrange the engineer's calculations, or build to your engineer's or surveyor's design, and we work with your architect or with independent architects we know where planning drawings are needed.
Removing a load-bearing wall always goes through Building Regulations, and a beam that bears into a party wall needs a party structure notice. Our guide to removing a load-bearing wall sets out typical 2026 London ranges: £2,500–£5,000 for a single internal wall with one steel beam, £4,000–£8,000 for a through-lounge knock-through and £8,000–£15,000+ for a large open-plan space with several beams, plus £500–£1,000 for the engineer's calculations. Every job is then priced from a site visit as a fixed, itemised quote.
Below ground, structural work starts with evidence. On our Limehouse Cottage project, trial pits, laboratory testing of the ground and a CCTV drain survey came first, and the engineer designed the underpinning, foundations and steelwork from those results. Underpinning on its own typically costs £40,000–£80,000 excluding VAT, as set out in our basement conversion cost guide; for new footings and drainage see groundworks, and for cellars and dig-downs see basement conversions.
Most of our structural work is part of a larger job, such as a renovation, an extension or a loft conversion, where the steelwork is planned into the programme from the start. We also take on structural repairs on their own, such as a bay that is carrying the floor above on its window frames. We are CHAS Elite and Constructionline Gold accredited, members of the Federation of Master Builders, work on JCT contracts and carry £10 million public liability insurance.
What We Do
Load-bearing wall removal and steel beams
Knock-throughs and open-plan ground floors on steel beams or goalpost frames, with the structure held on temporary supports and the steel boxed in and plastered. See our guide to removing a load-bearing wall.
Underpinning
Deepening existing foundations in sequenced concrete pins, designed by a structural engineer after trial pits, for extensions, lowered floors and basements.
Bay window rebuilds
Load-bearing bay posts, new lintels or steel ring beams for bays carrying the structure on their window frames, with original brickwork and details put back. See bay window structural problems.
New steel frames and structural rebuilds
Replacing the structure of lower floors with new footings and a steel frame of columns and beams, with fire protection to the steel.
Lowering floors
Lowering a ground floor or cellar floor for more ceiling height, with underpinning where the existing foundations need to go deeper. See basement conversions.
New foundations
Trench-fill, strip and pad foundations for extensions and structural alterations, with drainage reworked where needed. See groundworks.
Chimney and masonry repairs
Stitching cracked masonry with steel rods and repointing, and fitting chimney support plates to the engineer's design.
Examples From Our Projects
- Finchley Two-Storey Bay, N3: a front bay carrying the floor above on its window frames, taken down to ground floor cill level and rebuilt with load-bearing bay posts, a welded 200x150 steel ring beam and reinforced lightweight blockwork tied into the house, with 53 original corbelled bricks salvaged and rebedded. Completed December 2025. See the project.
- Hammersmith Terrace, W6: the lower ground and ground floor structure replaced on new footings with a new steel frame of 254 and 203 universal columns and beams, bolted at the joints and fire protected, and the chimney stitched with steel rods, before a new loft floor went on top. Completed April 2026. See the project.
- Bow Victorian Terrace, E3: the ground floor lowered for more ceiling height, underpinning, new trench-fill and pad foundations, and a structural steel frame fabricated off site and installed in one operation to open up the ground floor. Completed October 2024. See the project.
- Limehouse Cottage, E14: underpinning, new foundations and structural steelwork to open up the ground floor of a period cottage, designed by the structural engineer from trial pits and ground testing, with a Thames Water build-over agreement for the extension. Completed September 2025. See the project.
Planning structural work?
Send us the drawings or a few photos
Tell us what you want to open up or what is cracking, and send any engineer's drawings you already have. We will arrange a visit and price the work as a fixed, itemised quote.
Send an enquiry Call 020 8080 8240CHAS Elite · Constructionline Gold · FMB member · £10M public liability
How we price
- A fixed price for the agreed scope. After a site visit we send an itemised quote, set out trade by trade and based on a complete specification, with no provisional sums for items we have not properly scoped.
- A JCT contract. The work runs under a JCT building contract, the Minor Works form on our published projects, with a defined programme.
- No change without a written price. If you change the scope, or the work turns out to need more than was agreed, we send a written variation with its cost first, and that work goes ahead only once you have agreed it.
- A 10-year workmanship warranty. It covers our workmanship and starts on the day the finished work is handed over to you.
The full wording is in our terms. For typical London figures, see our cost guides.
Frequently Asked Questions
Do you arrange the structural engineer?
Yes. We can arrange the structural engineer's calculations for a beam, underpinning or a rebuild, or build to the design of an engineer or surveyor you have already appointed. On our Finchley bay rebuild a chartered building surveyor designed the repair and inspected the work, and on our Limehouse project the structural engineer designed the underpinning, foundations and steelwork.
How much does it cost to remove a load-bearing wall in London?
Our guide gives typical 2026 London ranges of £2,500 to £5,000 for a single internal wall with one steel beam, £4,000 to £8,000 for a through-lounge knock-through and £8,000 to £15,000 or more for a large open-plan space with several beams. The engineer's calculations add around £500 to £1,000. Your job is priced from a site visit.
Do I need Building Regulations approval for structural work?
Yes. Removing a load-bearing wall, fitting a steel beam, underpinning or rebuilding a structural bay all alter the structure, so they need Building Regulations approval with structural calculations. Building Control inspects the work, including the steelwork before it is covered up, and issues a completion certificate at the end.
Will I need a party wall agreement?
Often, on a terrace or semi. If a new beam bears into a wall shared with a neighbour you must serve a party structure notice at least two months before that work, and digging near a neighbour's foundations, as with underpinning, needs notice too. We coordinate the notices and work with the appointed surveyors.
Can you rebuild a cracked or sagging bay window?
Yes. The repair depends on what has failed: bay poles under the existing windows, a new lintel, a partial rebuild or a full rebuild on a steel ring beam. On our Finchley project we rebuilt a two-storey bay down to cill level and refitted the original windows, corbels, render and fascia so it looks as it did from the street.