Structural Steel Mezzanine Floor in Atria Shopping Centre Watford

T&B Contractors contracted LSJ Engineering to supply and fit a structural steel mezzanine floor to a shopping unit in Atria Shopping Centre, Watford, Hertfordshire. The steel beams total 89 tonnes, and we began work in July 2023.

The structural steel beams were delivered to the basement service area, then hoisted two floors up to the work area via a scaffold lifting gantry. The existing columns, some of which are nearly 5 inches thick, were drilled on-site to accept the new beams. The beams were erected with Genie lifting hoists.

You can click on the images below to see the works in progress, from the 3D model to the finished structural steel mezzanine floor:

3D model of a structural steel mezzanine floor
view of ceiling in shopping unit in Atria Shopping Centre, Watford
installation of a steel beam in mezzanine construction
steel beam installation in shopping unit
mezzanine floor at Zara shop in Atria Shopping Centre, Watford.
worker with steel beam in shopping unit
view of shop floor during installation of structural steel mezzanine installation

Once the steelwork is complete, the beams will be intumescent painted. Then a concrete deck will be poured on, in order to form the new floor. Finally, we will form new openings in the existing steel structure below to allow installation of new lifts and escalators. Building Design Consultants of Billericay designed the structural connections for the new beams for us.

We’re pleased with how this project is unfolding! What do you think of it?

Are you looking for structural steel work?

We are open for commercial structural steel projects! You can contact the team here, or email us via info@lsjeng.co.uk. Alternatively, phone us on 01702 290 585. You can find other structural steelwork projects here. We look forward to hearing from you.

Strengthening Beams at Atria Shopping Centre, Watford

In April 2023, T&B appointed LSJ Engineering to fit strengthening beams to concrete flooring in Watford, Hertfordshire.

Due to cracks found in a concrete floor slab at the Atria shopping centre, T&B appointed our team to erect 11 strengthening beams to the underside of the concrete. These beams were delivered at night and weighed nearly 800kgs each. Due to their size and weight, the beams were lifted with specialist floor cranes. You can see before-and-after photos below.

Note: you can click on the images to enlarge them.

work in progress installing steel strengthening beams under concrete floor
steel strengthening beams on underside of concrete floor, as seen from below


The works were completed in less than 2 weeks, which is well within critical timescales. Working to a timescale is extremely important when ensuring concrete is structurally safe! We’re glad we could help, erect the strengthening beams and turn this job around quickly so the Atria shopping centre can continue operating and welcoming visitors.

Are you looking for structural steel work?

We are open for commercial structural steel projects! Contact the team here, or email us via info@lsjeng.co.uk. Alternatively, you can phone us via 01702 290 585. You can browse other structural steelwork projects here. We look forward to hearing from you and discussing your project.

Office Block Steelwork Refit for Structure Tone at Golden Square, Soho, London

In late 2021, LSJ Engineering won the steelwork contract at 30 Golden Square, in London’s busy Soho area. This was a job for a new client, Structure Tone, with a contract of over £350,000. The job was logistically quite a challenge as the steelwork requirements were fairly substantial… and because Golden Square is quite busy to say the least!

  • Client: Structure Tone
  • Job Duration: November 2021 – present
  • Project Manager: Jeff Beverley

Beginning the Project

A six-storey office building undergoing a refit, this property was completely stripped back to its bare structure of part-concrete, part-steel work. We added extensions to the rear of the building, from the basement to level six. Additionally, we added front elevation from levels five to six, in order to provide more floor space. Quite a tall order (pun intended!) but we enjoy jobs that require our expertise.

Needless to say, this job was a logistical challenge due to its many components. Our steel frames were delivered by HIAB lorry and wheeled into the building on trolleys, then lifted to each floor level via an internal hoist, which was provided by Structure Tone. Once the frames were at floor level, we erected them with chain hoists from scaffold lifting beams, which were set at agreed points. With the frames erected, our team added a whole new level seven and level eight to the existing roof. We also added a plant deck.

Cellbeams formed the main roof beams, supplied by Westok. Cellbeams are a specialist, relatively lightweight, beam with pre-cut service access holes known as cells. Cranked columns supported these cells at each end to from the new roof’s shape.

Here is some of the work in action! (Please note you can click on the images to make them larger.)

red steel frame on London building
red steel frame and construction work, London
workmen on construction site on roof in London

The Roof Extension

Now for the next part of the job: the roof extension. The new roof was lifted and erected using a 90-tonne mobile tower crane, which was sited in Golden Square at weekends.

tower crane in Golden Square, London

Once we booked road closures and crane dates, our steel frames needed to be ready for lifting into place. If we didn’t prepare sufficiantly, the job could be delayed by weeks! Our professional, experienced team hit every date required and the job proceeded smoothly. Anything not erected by crane was lifted manually during the week using Genie lifts. This weekday work kept the job flowing, which is really important in a construction job.

Strengthening Works

The extra weight of the new floor, roof frame and RC roof slab meant the existing steel structure needed considerable strengthening for safety. We added some new steel to the floor below to support columns. This included a two tonne Cellbeam, hoisted and erected by hand using chain hoists.

Here is some of the team in action (with high-vis and hard hats, of course!):

man in high vis jacket with red steel and scaffolding in London
men in high vis jackets with red steel and scaffolding in London
red steel beams on ground in Soho, London

The strengthening works involved welding 20mm and 40mm thick steel plates to the flanges of some of the existing Cellbeams for their entire 10m length. It also required infilling some cell holes at critical points. This site welding alone took a gang of welders over two weeks to complete! We subcontracted the welding to City Arc Group, who did a very professional job, with no failures when tested.

We’re pleased that the works are mainly complete, with a few secondary steelwork areas awaiting completion.

LSJ Engineering was also awarded the architectural balustrading package of over £100,000, to begin shortly. We’ll update you when it’s underway…

We’re very pleased with the outcome of this project. It was quite the job, but our team rose to the challenge brilliantly, as always, and we worked with some very professional industry colleagues throughout the process.

Are you looking for structural steel work?

We are open for commercial steel projects! Contact the team here, or email us via info@lsjeng.co.uk. Alternatively, you can phone us 01702 290 585. You can browse other structural steelwork projects here. We look forward to hearing from you and discussing your project.

Feature Staircase at Mortimer St, Mayfair, London (Mortimer St Part Two)

Last summer we shared the start of a project at Mortimer St, in Mayfair in London. That job – part of a building refurbishment – was a vertical extension. Here is the second part of the project: an unusual featured staircase!

GPF Lewis awarded the LSJ Engineering team the contract to complete the design, then build, a feature staircase at their Mortimer St refurbishment.

Barr Gazetas provided the original staircase design. It showed slim stringers, cut to follow the shape of the treads. The plan included a half landing, supported by hanging it from the floor slab above on four 20mm diameter rods, with a balustrade fixed to the stringers. It runs up through the void in the floor to form the balustrade around to void at that level.

Note: you can click on the images to enlarge them.

Not a standard design! We carried out a lot of structural design checks to make sure the stair didn’t sway when used. Draft SD carried out the drawings and modelling work.

We’re delighted that we achieved a close match to our design brief. The stringers were laser cut from 25mm solid plate to ensure clean lines, and we built the balustrades in the workshop for maximum accuracy before dismantling them for their powder coated finishes, as well as the delivery to the fourth floor of the building.

What do you think of the finished product? We’re very pleased with the featured staircase, and we’re chuffed to have finished our work at Mortimer St on a high. It was especially satisfying to include two slightly different elements of our trade on one project.

Do you require a feature staircase for your commercial building?

We are open for commercial steel projects, including staircases. Contact the team here, or email us via info@lsjeng.co.uk. Alternatively, phone 01702 290 585. Browse write ups of our other staircase projects here. We look forward to hearing from you.

Architectural Balustrades, Privacy Screens and Steel Handrails for a New Build in Wimbledon, London

GPF Lewis appointed us to work on a new block of flats at 192 Merton Road in Wimbledon. (You may remember GPF Lewis from our work with them at their Mortimer St refurbishment project.) This was quite a detailed job, with many parts to it!

Our client commissioned us to design, supply and fit balustrades to three levels of balconies, plus the perimeter of the fourth floor roof. In total the project required over 90 linear metres of balustrades.

steel architectural balustrades on balcony in Wimbledon, London
steel architectural balustrades on balcony in Wimbledon, London

We also supplied privacy screens to go between the different flats. There are 27 apartments in total (23 in the main block, plus 4 penthouses on the fourth floor). As you can imagine, this was quite a lot of work for our team – but we love jobs we can get our teeth into! Feel free to click on the images to enlarge them and get a better view of the screens and balustrades.

balcony with steel balustrades and screen
balcony with steel balustrades and screen
balcony with steel balustrades and screen

Finally, we supplied stainless steel wall fixed handrails for the main staircase, as well as gates for the main entrance. (We also supply steel staircases for commercial properties if you’re interested!)

What do you think of the finished job? We’re really pleased with it, and we hope Merton Road’s new residents love their homes.

stainless steel handrails in flats, Wimbledon
stainless steel handrails in flats, Wimbledon
stainless steel handrails in flats, Wimbledon
stainless steel handrails in a staircase in flats in London
stainless steel handrails in a staircase in flats in London
stainless steel handrails in a staircase in flats in London
stainless steel handrails in a staircase in flats in London
stainless steel handrails in a staircase in flats in London
steel entrance gate at Merton Rd, Wimbledon, London
steel entrance gate at Merton Rd, Wimbledon, London

Are you interested in commissioning architectural steel work from LSJ Engineering?

We’re available for architectural steel work! Contact the team here, email info@lsjeng.co.uk or phone 01702 290 585. You can read about our other architectural steel work here. We look forward to hearing from you!

Vertical Extension at Mortimer St, Mayfair, London (Mortimer St Part One)

GPF Lewis commissioned LSJ Engineering as the structural steel contractor in a building refurbishment. This was the first part of our work at Mortimer St (the second part is this feature staircase).

We are the appointed structural steel contractor to GPF Lewis, the main contractor refurbishing a building in Mortimer St, W1.
This is a very complicated job as the main part of the works is a vertical extension forming a new 5th floor level. The 5th floor of the building is currently the roof of the 4th floor!

crane and steel work against sky
bird's eye view of the ground from vertical extension work at Mortimer St, London
crane moving steel bar at Mortimer St, London, as part of steel works and vertical extension
crane and steel work being moved at a vertical extension in Mortimer St, London

We have had to strengthen the existing steel frame at critical points of the current roof level in order to take the new structure’s weight… The total weight of steelwork alone is over 60 tonnes! Some of the new cranked roof beams weigh over 2 tonnes, and the only way to get these to the new level is by lifting them with a mobile crane. GPF Lewis arranged for several weekend road closures to set up a 130 tonne mobile crane and lift the new steelwork into place.

Here are some more of our photos and, excitingly, some drone footage taken by GPF Lewis! You can find their write up of the project here. We hope you’ve found this post interesting – if you’d like to read about our feature staircase work on the same project, click here.

view of a vertical crane as part of steel work at Mortimer St, London

Are you interested in commissioning steel work from LSJ Engineering?

We are available for steel work projects! Get in touch here or email info@lsjeng.co.uk. Alternatively, phone us on 01702 290 585. You can find more of our structural steel work projects, including other vertical extensions, here. We look forward to hearing from you.

Steel Staircase for WeWork, Blackfriars Bridge, London

LTB appointed us to design a basement-to-ground-floor steel staircase at a new WeWork office just south of Blackfriars Bridge, London. This is one of a handful of jobs we’ve done for LTB at WeWork offices over the years (here are the others!).

  • Client: LTB
  • Structural detail by: Mark Ebbs
  • Job Date: December 2020

The staircase needed to span over 9 metres, without support posts. This is normally achieved with an off-the-shelf structural steel section such as channel or box section. In this case, however, the stringer had to look as slim as possible. Furthermore, it could be no wider than the balustrade bolted to it. Our team achieved the desired specifications by fabricating a hollow box section from 15mm plates, welded together to make a section size of 400mm x 75mm. The plates were fully welded together to give the strength required. The welds were ground flat to achieve a clean look.

Each stringer was made in two sections and spliced back together on site before erecting. Here is the staircase in our workshop:

Each stringer, once assembled, weighed over 800kgs! We took great care to avoid damaging the finishes. Roustabout lifting gear erected the stringers.

The balustrade is bolted directly to the top of each stringer. Because it needed to fit perfectly, we assembled the stair and made the balustrades on the stringers in our workshop. Then we dismantled it all and sent it to be powder coated by Mulberry and Pier.

We also delivered a raised floor area and ramp balustrade for the ground floor, in the same style. We delivered and completed the works in plenty of time before handover. There was also minimal touching up of the paintwork!

What do you think of the finished staircase?

Note: you can click on each photo to enlarge it.

Interested in commissioning a steel staircase from LSJ Engineering?

We are open for commercial steel work! Get in touch with our team here or email us on info@lsjeng.co.uk. Alternatively, call 01702 290 585. We look forward to hearing from you! You can view write ups of our other staircase projects here.

Steel Staircase at Project Q, Thames Barrier, London

LSJ Engineering built a steel staircase for Project Q at London’s Thames Barrier in autumn 2020.

Construction management company Chisholm and Winch employed us to design, supply and fit a steel staircase to the new Thames Barrier control building in south east London. Balfour Beatty. constructed the new Thames Barrier building.

This was a simple stair… except that the half landing had to be radiused on-plan, in order to match the reinforced concrete (RC) frame of the adjacent wall. Following an electronic laser survey of the curved RC wall, we built the stair to fit. Furthermore, Chisholm and Winch needed to ensure that the build up of insulation and plasterboard, applied to the RC, perfectly matched the wall. Bearing this in mind, we trial-built the stair at our works in Shoeburyness, Essex. This allowed us to check that the rolled stringers perfect fit the laser-cut landing plates, and fit the wall without gaps or clashes.

Once powder coated a rather bright yellow off-site, the stair was delivered and fitted without any issues!

What do you think of the finished product? Although a complex job, our team worked brilliantly to ensure we fulfilled our brief.

Do you require a steel staircase for your construction project?

We are open for commercial steel projects. Contact the team here, or email us via info@lsjeng.co.uk. Alternatively, you can phone us on 01702 290 585. You can view write ups of our other staircase projects here.

External Staircase Replacement in Harrow

ACAI Group commissioned LSJ Engineering to work on a commercial property in Harrow, Greater London. The property included a badly corroded external staircase, so our team designed and fitted replacement.

The existing stair (probably in excess of 20 years old!) did not conform to current regulations. Unfortunately, the replacement stair did not meet regulations either, due to space restrictions. Permission was, therefore, granted by Building Control to replace ‘like for like’ in terms of tread goings and risers.

At the time of this project, our in-house drafting facilities were very busy on other projects, so the design work and drawings were carried out by Sam Thewsey of DSD Ltd.

This was an office access stair, so we carried out the removal and replacement over 4 long days, partly over a weekend in order to minimise disruption to the businesses.

The new stair stringers, treads and balustrade were hot dip galvanized for durability.  What do you think of the finished staircase?

Note: you can click on the images to enlarge them.

An external staircase replacement in Harrow: https://lsjengineering.co.uk/2021/01/04/external-staircase-replacement-in-harrow/

Do you require a replacement external staircase?

We are open for commercial staircase work. You can get in touch with the team here, or  email info@lsjeng.co.uk. Alternatively, phone us on 01702 290 585. We look forward to hearing from you! You can view write ups of our other staircase projects here.

Feature Staircase for Xero, Kings Cross, London

Denton Associates commissioned LSJ Engineering to design a feature staircase for an office fit out for Xero in Kings Cross.

The challenge on this job was that the stair ran from 7th to 8th floor levels, and the only access was via a 2.5m long lift. This meant that all the stair stringer and balustrade sections had to be less than 2.5m in length! They still required powder coating off site.

Our team designed the stringers to have neat joints. This allowed them to be bolted together once we got them to the correct level. It also ensured the stingers are as strong as if they were on one piece. The half landing support posts formed an ‘X’ to reflect the end client’s logo.

The perforated balustrade panels were bespoke, punched to form neat borders around each balustrade, while the copper handrails were fitted by others.

LSJ also undertook the demolition works to form the stair void opening in the 8th floor slab. We subcontracted to Evolution Enabling of Rayleigh, who installed a crash deck, saw cut and removed the slab, which was equally as challenging as the stair install.

A feature staircase for Xero at King’s Cross, London: https://lsjengineering.co.uk/2020/12/29/feature-staircase-xero-london/

Are you interested in commissioning a feature staircase from LSJ Engineering?

We are open for commercial steel and staircase work! Get in touch with the LSJ team here, email info@lsjeng.co.uk or call 01702 290 585. You can view write ups of our other staircase projects here.