Invisible Connections is currently working with precast concrete and DfMA specialist SCC Design Build to construct stair cores at Manchester Airport.


Manchester Airports Group (MAG) is undertaking a transformation programme that will position the airport as a ‘Global Gateway’, offering more routes and creating increased economic growth in line with aviation forecasts.

As part of this development the airport is expanding its terminal facilities, apron space and customer car parking facilities to accommodate increased demand.

With many MSCP projects already to its name, SCC Design Build (working for BAM) successfully manufactured and constructed the precast concrete frame and cores (incorporating flights and landings) at the newly completed 6,500 space ‘meet and greet’ MSCP at Terminal 1 and Terminal 3.

As part of its innovative build process, SCC Design Build (‘SCC’) used telescopic connectors by Invisible Connections extensively throughout the structural frame and cores, being SCC’s tried and trusted connection solution for rapid construction.

With a clear pedigree in car park construction and an existing presence on the airport, SCC was the natural choice by Galliford Try for the newest 7,669 space car park that will link to Terminal 3 and have buses to the other terminals.

Although a steel frame was chosen for this latest car park, SCC was appointed to construct the stair cores in precast concrete, chosen for its fire properties and the stabilisation of the structural steel frame.

There are 10 stair cores in total, which vary in height up to 5 storeys. All 10 cores incorporate precast flights and landings, with 6 of the cores also housing the lift-shafts.

Building on the success of several previous project collaborations, Invisible Connections was chosen by SCC for its landing-to-wall system of telescopic connectors. The RVK101-30 pinned connection detail was specified to tie landings to the core walls (tying into REDiBOX PIN recess formers) thereby satisfying the Engineer’s design requirements for robustness.

It’s increasingly common to combine precast concrete stairs and landings with core walls which are either precast or poured in-situ. When connection methods are left as an afterthought, using traditional rolled steel support angles is often the only practical, yet inefficient, fixing solution.

With a little up-front planning, there’s much to gain by incorporating telescopic connectors, which come with a host of advantages; such as improved health and safety, robustness compliance, and significantly improved cost effectiveness. Indeed, a recent study found that using telescopic connectors instead of rolled steel angles reduced man hours by 80%, which contributed to a total 33% reduction in direct costs.

Throughout the design, manufacturing, delivery and installation stages, Milbank Concrete Products offer one of the most comprehensive and professional service packages, providing a range of precast concrete products including: balconies, beam & block flooring, bespoke concrete products, ground beams, hollowcore flooring, helical stairs, rail products, sea defence & flood solutions, stadia products and straight stairs & landings.

Following on from market research and the identification of the need for an affordable, cost effective and efficient thermal floor arrangement, Milbank Concrete Products have recently launched their new and improved insulated concrete flooring solution, WarmFloor Pro.

WarmFloor Pro offers construction professionals a cost-effective alternative to quickly assembling a thermally insulated concrete ground floor over the industry leading competitor brand, Jetfloor, by Forterra (Bison). Reduced initial construction costs and an increase in energy savings make WarmFloor Pro a compelling alternative to a standard beam and block floor. In combination with its certification and A+ Green Guide rating, WarmFloor Pro is proving to be a must have addition to any new, eco-friendly development where keeping heating costs low is paramount.

WarmFloor Pro is suitable for almost any structure, but is most commonly used in housing, from single dwellings to complete housing developments. It offers a simple, cost effective, concrete insulated flooring solution to self-builders and construction professionals alike. Without the need for any specialist tools or skills, installation of WarmFloor Pro is efficient and streamlined whilst minimising waste and emission rates.

WarmFloor Pro works by combining rigid insulation modules (EPS panels) manufactured from lightweight closed cell expanded polystyrene which is laid in-between prestressed concrete beams (either 155mm or 225mm deep) with an EPS top sheet, damp proof membrane and structural concrete topping. If required, underfloor heating can be incorporated with the pipework attaching to the EPS panels with plastic pegs before the concrete topping is applied.

WarmFloor Pro is comprised of 6 main EPS components that are available in two types of EPS; standard issue in white (0.038W/m²K) or an alternative high-performance platinum in grey (0.031W/m²K). The 6 components are made up of Top Sheets – available in depths of 75-150mm, Infill Panels – available in 533mm for nominal 600mm beam centres and 343mm for reduced beam centres, and End Panels – available in both 178mm and 300mm.

EPS end panels are used for both the start and end of the flooring installation. The end panels are inserted at the start of the row with the straight (1200mm edge) opposite to the beam. All units are 1200mm long and can be cut on site to the required length using basic tools such as a handsaw; (minimum 300mm long).

As every building is different, Milbank are well equipped to design your floor to achieve the specific targeted U-Values (reaching as low as 0.07W/m²K) together with the structural layout of the floor to suit. Milbank then manufacture the concrete components and supply the materials (including the EPS panels) directly to your site. WarmFloor Pro is currently available on a supply only or supply and installation basis using their vastly experienced installation teams.

WarmFloor Pro Benefits:

  • Easy to install – does not require any specialist tools or skills.
  • Quick to install – each EPS panel is the equivalent length of 5 standard concrete blocks.
  • Cost effective – WarmFloor Pro is designed to save you money. Faster installation speeds combined with reduced waste and excavation removal allow for an increase in overall savings.
  • Bespoke – a wide range of EPS panel depths and grades are available to satisfy your U-value or budget requirements.
  • Sustainable – WarmFloor Pro is designed to last the lifetime of the building while maintaining its exceptional thermal performance.
  • Clean, safe and easy to handle – lightweight EPS panels only weigh around 2Kg.
  • Underfloor heating compatible – heating pipework is simply held in place using plastic pegs that push into the EPS panels.
  • Proven Technology – now in use for over 10 years.
  • Industry compliant – Milbank WarmFloor Pro is Fully certified and has an A+ green guide rating.

For more information on Milbank Concrete Products or to enquire about their extensive range of products including WarmFloor Pro Insulated Flooring, please visit their website or call them on 01787 223 931.

St. Andrews University in Fife chose Creagh Concrete for the first stage of their £70million investment plans in student accommodation for the university. MMC Magazine Editor Joe Bradbury finds out more:

A building of historical significance

Founded in the 15th century, St Andrews is Scotland’s first university and the third oldest in the English speaking world. Teaching began in the community of St Andrews in 1410, and the University was formally constituted by the issue of a papal bull in 1413.

In 2009, St Andrews became the first Scottish ancient to appoint a woman as Principal, recruiting Professor Louise Richardson from the Radcliffe Institute, Harvard, to lead it into its seventh century. She was succeeded in 2016 by Professor Sally Mapstone.

St Andrews recently celebrated 600 years of continuous existence during which time it has made an enduring contribution to the intellectual and cultural life of both Scotland and the wider world.

Project overview

The first stage of the investment called for two new accommodation buildings for the campus. The new buildings called Powell Hall and Whitehorn Hall respectively have created 389 new bedrooms for the university.

Creagh provided architectural concrete cladding for the buildings including feature walls with etched lettering. In total, Creagh installed 695 GFRC concrete pieces for both projects. Glass Fibre Reinforced Concrete or GFRC (also known as GRC) is a type of fibre-reinforced concrete. GRC consists of high-strength glass fibres embedded in a concrete matrix. Both fibres and matrix offer a synergistic combination of properties that cannot be achieved with either of the components acting alone. The fibres provide reinforcement for the matrix, increasing its tensile strength, limiting the shrinkage and creep processes as well as eliminating curing cracking appearance.

For the St Andrews project, Creagh developed a project-specific GRC mix to match both the structural performance and aesthetics requirements. This allowed the installation of floor to floor panels with 25mm concrete skin and no steel rebar. Creagh’s manufacturing facility rose to the challenge of precise filigree moulding and different casting techniques required for the panels.  Among the benefits of GRC: it’s reduction in thickness provides an increased cavity and/or insulation allowance and a smaller loading to the façade. All of which significatively reduce the buildings carbon footprint but providing the same durability and resilience as traditional concrete.

Powell Hall opened its doors to postgraduate students for the first time in October 2018.  It is named after Renee Powell, American professional golfer who became one of the first female members of the R&A in 2015 and was the second African -American woman ever to play on the LPGA Tour.  The new building is five-storeys and adjacent to Agnes Blackadder Hall on the North Haugh, near the various science buildings.  It is also located near to the Sports Centre and is only a 15 minute walk to the town centre.

Aluminium copings were also installed on Whitehorn building, a four-storey building located adjacent to University Hall, near to the Sports Centre and the various science buildings on the North Haugh. It is named after Katharine Whitehorn – British journalist, writer and columnist, and first female Rector of the University of St Andrews from 1982 to 1985.

The decision to use precast concrete systems for the bulk of the building’s structural frame, cladding and balcony units was taken at an early stage on the project. The brief demanded a robust finish on the building, which would limit the amount of ongoing maintenance required.

Precast concrete is the ideal material of choice for frame construction and cladding.


Rising to the challenge

The job itself was not without its challenges. Speaking with MMC Magazine, Contracts Manager Ramon Escriva said “On the technical side, it was a very difficult installation with most of the panels with no access to fixings. We devised a range of different solutions to provide fixing points. There were also several cases with overhung panels that required special craneage arrangements.”

Creagh Director and Co-Founder Seamus McKeague added “We are seeing strong interest in our rapid build concrete systems because developers now understand the true value of slashing programme times.

“Investors not only benefit from revenue gained by the early occupation of units but, also, from the mobility of their capital resource. Quite simply, shorter build times mean developers can complete more projects with the same pot of finance.”

The brand new building offers various facilities for students to use for studying and/or socialising including, main social space, games room, cinema room, private dining room, sound insulated music room, study spaces, kitchen/lounges & a laundry room.

The new additions to the halls of residences will increase residential space offered by the University from 4,000 to 4,900 occupants, in an effort to accommodate the increase of students attending the University.

Tackling the severe accommodation shortage

From a political point of view, this project couldn’t have come at a better time, with Scotland facing a “clear problem” with providing accommodation for university students on campus.

In a recent article in the Scotsman, Green MSP Mark Ruskell called on the Scottish Government to hold a summit of university accommodation providers and student representatives to tackle the issue. Speaking at Holyrood, he said “I think it is clear that we have got a problem across Scotland.

“At Stirling University 180 first year students didn’t have accommodation last year. Under-18s cannot rent in the private sector, care leavers and international students struggle to find guarantors for private contracts. Disabled students very rarely find the appropriate private accommodation to meet their needs and we see increasing rents on campus as well.”

About Creagh

Creagh Concrete has been a pioneer of precast for over 43 years.  They are one of the UK’s largest producers of concrete products for a diverse range of market sectors throughout the UK and Ireland.  Creagh is leading the market with innovation in concrete, providing new solutions across the construction industry, changing the way people think about concrete, bringing new levels of efficiency and performance to their products.

The company operates from its head office in Toomebridge, Northern Ireland with bases in Ardboe, Dunloy, Draperstown and Magheraglass and also at Nottingham, England and Edinburgh, Scotland.

We asked them what their ethos is and this is what they said:

“Creagh is all about quality products & relationships – strong relationships with our customers, sub-contractors, clients and suppliers.  These relationships are key to our business and our approach to working together to deliver successful projects. From initial design consultation, through project development, groundworks, installation and beyond, your scheme couldn’t be in more experienced hands.”

FLI Carlow are the premier total service provider of engineered structural solutions to the Water, Energy, Storm Attenuation and Bespoke markets.  Our capacity to design not just the precast units, but the structure into which they integrate and the manufacturing tools used to make them has kept us at the forefront of innovation in our industry.

Semi-precast is the core of our business, a hybrid between traditional in-situ concrete and traditional precast.  Although sometimes seen as an under-developed off-site manufactured solution, the semi-precast design philosophy brings enormous improvement to cost and construction efficiency.

The semi-precast approach aims to deliver solutions fully compliant with the operational design requirement.  The ideal configuration is not adapted to prefabrication.  Whereas we will identify cost and time saving opportunities during the design development phase, we can adapt to the most precise configurations for operational accuracy.  In principle, any structure imagined in in-situ concrete can be delivered in semi-precast.  Approving Authority confidence is engendered by implementing designs which cannot be disproved by failure to comply in any respect with the specified codes and standards, whether national, international or customer specific.  We place wet concrete against hard concrete, the way it’s always been done.  The difference is that some of the concrete was manufactured elsewhere and the location of joints and interfaces are unconventional.  Regardless, the integrity of joints and interfaces remains uncompromised and verified by design.

The Benefit of Prefabrication

We complete the difficult parts of construction in our factory, under ideal conditions and under quality supervision.  Features including pipe-fittings, nibs, corbels, launder-channels, formwork attachments and stability-footings (among others) are eliminated from the site works.  Products are delivered to site on a just-in-time basis then taken from the delivery vehicle to their service position in one simple operation without fuss or temporary propping.  Small crews achieve amazing productivity by following simple steps and using well designed components and delivery systems.


Precast concrete units can weight in excess of 20 tonnes.  Under normal manufacturing tolerances, it could be very difficult to ensure the precision required to maintain accurate alignment and watertight fit.  The in-situ joint provides a transition between elements which ensures a complete and perfect fit (in it’s liquid phase) and a completely ‘relaxed’ structure at introduction to service.  We don’t stress pieces into alignment or position.  The design assumptions are fully realised.

Waterproofing Integrity

At every interface a scabbled surface is prepared.  In addition, a smooth dense slot is preserved for the application of hydrophilic strip.  This provides ongoing self-healing capability in service.   We use only one hydrophilic product; Denso Hydrotite.  Hydrotite is resilient to inflation prior to encasement in concrete.  It can compress against the surrounding concrete with a pressure of up to 3MPa on contact with water and has been approved by Tokyo Underground for design life up to 100 years. It is also DWI and Materials in Contact approved for potable water applications in the UK. That’s 100 years to first significant maintenance of the structure – no compromise.  Sealants used at the mechanical interfaces of traditional precast concrete tanking structures rarely have a service life in excess of 20 years.  These features are particularly relevant to storm attenuation, storage, treatment and basement applications,

Structural Continuity

Although relatively short, the in-situ joint is used to enable two-way bending of the structure.  This capacity is not available using any other precast approach.  Reinforcement lap lengths are designed on a bond-stress basis to ensure full capacity in smaller spaces.  Even the interface between the in-situ concrete stitch and the precast unit is designed for the same crack-width control as the body of the structure.  This ensures that all elements of the structure provide the minimum standard of waterproofing integrity and full compliance with concrete structures design standards.

By bending in both orthogonal directions, structures are thinner, lighter, economical, require less transport, less craneage and have a lower carbon cost.


Our particular concrete mix design delivers very high early strength for efficient production, typically, 25 Newtons at 16 hours.  This ensures maximum safety and maximum value by extracting products daily.  We use very high concentrations of GGBS (66%) which in conjunction with other energy and carbon saving measures has reduced our carbon cost from 278kg/tonne of concrete manufactured to 182kg/tonne.  To ensure the high early strengths despite the use of GGBS we use thermal activation.  By adding mixing water at up to 80°C the disadvantage of slow strength development of GGBS is eliminated.

Sulphate Resistance

High levels of GGBS when used in conjunction with limestone cement and limestone powders (for self-compacting behaviour) produce a design chemical resistance class DC4.  That’s sulphate resistant concrete at no additional cost.


The precast unit is delivered to site with projecting reinforcement often from five of it’s six faces.  All components are 3D modelled prior to manufacture and assembled in model-space prior to fabrication.  This eliminates the risk of clashing reinforcement and disruption to programme.  Projecting reinforcement leaves very few bars to be placed on site.

Typically the vertical in-situ stitches represent 30% of the volume of the perimeter and internal walls.  While precast concrete products are relatively expensive (although value-adding), the concrete used in the joints is locally sourced readymix at approximately £40 per tonne.

The formwork required is very light.  Shuttering ply facing with vertical stiffeners is locked against the structure using steel braces and MKK cone anchors.  The advantage in this low cost approach is that the formwork is torsionally flexible adapting easily to the surfaces on which they bear.  Smooth transitions and tight interfaces are achieved. Through-ties are completely eliminated.  These are often a problematic feature of conventional in-situ works.

Length of Joints

The number and length of joints in our solutions are often questioned.  Our industry sees joints as the most problematic elements of waterproof concrete construction – more joints, more risk.  The rebuttal is that it’s not the number of joints you fear, but the distance between them.  Traditional construction methods utilise joints at 6m – 10m centres.  Thermal and drying shrinkage accumulate over these lengths and are concentrated at a single interface.  The precast unit has long completed its shrinkage when placed on site therefore the shrinkage to be addressed is that occurring over only 500mm.  In addition, each interface has the benefit of a factory prepared scabble, reinforcement continuity designed to the higher standards for crack-width control and a self-healing strip at each end.  The semi-precast interface is subject to only between 5% and 10% of the movement occurring at conventional joint.  As a result, it is significantly better preforming than conventional concrete in this respect.

Rate of Construction

Semi-precast structures are typically completed in 60% to 40% of the time taken to deliver conventional structures.  This is where the value lies, both in terms of reduced preliminaries and hugely increased productivity. During the conventionally difficult construction of vertical and suspended works, equivalent productivity per person on site is ten times greater.

For more information, call us on +44 (0) 1279 423303 or email us at You can find us on the web at the below address.

Kerkstoel 2000+ manufacture so called twin walls and lattice slabs, these products combine the advantages of precast with insitu placed concrete.

Kerkstoel 2000+ is one of the most innovative concrete companies in Europe. It is part of the Kerkstoel Group and is based in Grobbendonk (Belgium).It specializes in the production of precast concrete walls and floors. Every precast element is made to measure in a highly automated factory. Based on the architect’s design (general arrangements and cross-sections), structural calculations, formwork and installation plans, Kerkstoel 2000+ develops an installation plan, with all the necessary details, so that everything runs smoothly and according to plan on site.

The floors, or lattice slabs, are used as a structural and aesthetic underside of a concrete floor. Basically permanent formwork they are the ideal substrate for concrete floors and can be made in all shapes, up to 7 cm thick. Wide plates are equipped with bottom reinforcement and on the underside they have a very smooth surface. After placing the lattice slabs and propping the top reinforcement is installed. Finally, the slabs are poured with concrete to the desired floor thickness. The result: a solid concrete floor where the load is perfectly distributed.

The reinforced twin walls of Kerkstoel consist of two shells of reinforced concrete that are connected to each other by lattice girders. All necessary built-in parts are provided in the walls during production (such as electrical boxes, power conduits, openings for windows and doors, wooden boxes, etc.).The wall elements are then assembled on site according to plan and then filled with concrete. The result is a solid construction as strong as a monolithic cast insitu concrete wall. These systems ensure high quality on site in a shorter construction time. The heavy skilled labour, such as steel-fixing and formwork, is limited to an absolute minimum. Thanks to the hybrid character, namely the combination between prefab concrete and in situ concrete, with the necessary water-bars  the walls can also be used for underground structures.

In 2018 Kerkstoel 2000+ invested in a brand new automated production hall. With this production hall, Kerkstoel wants to further specialize in the concrete wall sector. Concrete walls with integrated insulation, sandwich panels, walls with prints, etc. will now also be be possible. Kerkstoel 2000+ has been active on the British market for more than 10 years, and has delivered walls and floor slabs to numerous contractors. Contact us and see what we can do for you!


Milbank Concrete Products recently worked alongside RG Group on the design, manufacture and installation of over 90 specialist precast concrete flint embossed retaining walls at the St James Retail Leisure Park development in Dover, with an estimated contract sum of circa £24m. 

The St James development has transformed the retail and leisure offer in the heart of Dover and south Kent and is located on the A20, the main road leading to the Port of Dover, making it highly visible and accessible to visitors, tourists and those travelling to and from the port.

The development comprises a range of outlets including an M&S store, a six-screen multiplex Cineworld cinema, a 108-bed Travelodge hotel and five national chain restaurants, along with a further 12 retail units ranging in size from 2730 to 16,000ft2 (254 to 1486m2). With over 450 car parking spaces and 156,915ft2 (14,578m2) of new retail and leisure space in total, the development is well equipped to cater for a large number of visitors on a daily basis.


Design and construction

Milbank produced 97 precast concrete walls in total, ranging from 6 to 11 tonnes, using four separate timber moulds. The complex moulds were handcrafted by skilled, in-house carpenters and specific requirements were agreed with regard to the flint layout by Dover District Council, Dover Planning Departments and the site contractors in co-ordination with Historic England, using examples of local existing flint walls. 

The flexibility of having four individual moulds allowed the production team to hand-lay the flint into two moulds, while the remaining two moulds were poured. The panels were cast over a ten-week period at Milbank’s precast concrete factory in Earls Colne. During the casting process, sand was used as a bed within the timber moulds to assist with the placement and spacing of individual flint stones, which were hand laid face down in the agreed style. Dover District Council visited the factory during the production period to assess the flint arrangement and to ensure it met its needs and gave the best possible match to existing flint walls and buildings in the vicinity.

To create the desired finish, the production team hand-picked the stones to ensure they all interlocked together neatly. Once this extremely time-consuming process was complete, steel cages, lifters and pipes were located and installed and the concrete carefully poured over the top of the flint stones to form the wall structures. The following day, once the concrete curing process was complete, the excess sand was washed off and the units were turned using the in-house gantry crane to present the finished article.

Milbank’s modern Sipe batching plant is capable of producing 35m3 of concrete per hour. For this particular project, a standard C40/50 strength-class concrete comprising of 460kg/3 of Portland cement, 1800kg/m3 of mixed aggregates and 40kg/m3 calcium carbonate fines were selected to create the desired finish and achieve the level of structural integrity required.



Installation and completion

Due to the size and weight of the wall units, with some weighing up to 11 tonnes and sitting at over 5m tall, a complex installation procedure was required involving the use of both 100-tonne and 80-tonne mobile cranes (lifting up to a radius of 17m) in combination with the specialist precast installation team. Due to the access restrictions on-site, short trailers were arranged for delivery ahead of schedule following on from an initial site consultation and the delivery vehicles arrived on a ‘just-in-time’ basis, allowing for the walls to be offloaded directly into position.

Each individual wall was located over projecting steel dowels and cast into the foundations on-site by the main contractor RG Group, a specialist in the retail, student accommodation and commercial sectors of the construction industry. Lined and levelled on shims and bedding, the walls dowel connections were fully grouted using specialist pipes cast into the rear of the structures during the manufacturing phase. The walls were designed with male-to-female connections to act as a shear key, which allowed the walls to act in unison and to reduce individual movement once installation was complete. 

Due to the walls being manufactured and installed as individual units, it was required that the joining sections be hand-filled on-site by the main contractor with matching flint stones to consolidate all units into one flowing piece. Finally, end columns and caps were also manufactured on-site by the main contractor to provide finishing touches to the wall structure. The flint walls now act as a screen to the service area for the main retail block from the roadside, which includes M&S and Next at the Dover St James development.