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Cross Laminated Timber (CLT) & its use in structures

Premier Guarantee Technical Standards Manager, John Gilbert, provides technical guidance on the treatment of Cross Laminated Timber. The recent interest in ‘modular buildings’ as a solution to the housing crisis and current skills shortage, has brought forward the potential use of ‘CLT’ (Cross Laminated Timber) as a structural panel to produce wall panels or indeed modular pods.

A number of CLT products have third party product approval for the use as a structural plank for construction uses. However, it is also important that manufacturers have a quality management process to ensure consistent quality. Usually these approvals and manufacturing processes are for the solid plank and therefore full designs of the construction including its external cladding. are required on a site by site basis. CLT as a structural timber product isn’t preservative treated. It is also difficult to ‘post treat’ the panels due to the compact layers of softwood timber making penetration of the preservative across the full cross section difficult to achieve. So, it is important that the design keeps the CLT panel completely dry, particularly at ground level and around critical junctions.

Where structural timber, such as these wall panels are to be used in an external wall construction consideration should be given whether timber treatment is necessary if the species of the timber isn’t sufficiently naturally durable.

The vulnerability of timber in external walls is particularly critical where the timber is positioned in certain areas including at the horizontal damp proof course without the inclusion of a treated sole plate. Whilst the use of CLT panels in external walls is a relatively new occurrence in the UK, wall panels incorporating CLT have been successfully used in Europe.
Premier Guarantee are actively involved with the Structural Timber Association and have recently supported and endorsed technical guidance produced by the STA. The recently reviewed CLT guidance is available via The Structural Timber Association and BM Trada.

For our warranty purposes

Where projects are proposed that incorporate CLT wall panels; they must not be used with a render or other cladding system that is directly bonded to the wall panel. A drained and vented cavity must be provided. The CLT panel must be suitably protected as follows:

At DPC level

The CLT wall panels can be positioned directly onto the horizontal dpc (over the substructure walls) without a treated timber sole plate providing that:

  • The DPC extends at least 50mm past the face of the CLT and in the case of on the cavity wall side- extends down 50mm below the horizontal DPC without bridging the cavity.
  • The lowest level of the CLT panel where it sits onto the horizontal dpc must be not less than 150mm above the finished ground level. The residual cavity must extend 225mm below the lowest horizontal DPC level.
  • Open brick perpends / Weeps should be sited under the external horizontal DPC in the cladding at 1200mm centres.
  • Measures to prevent cold bridging at the substructure wall / ground floor / CLT wall panel junctions must be in place.
  • Ground levels immediately in front of the external wall should slope away from the building cladding.
  • CLT panels must not be constructed into ‘troughs or pockets’ e.g. for an internal wall panel on a structural slab. The risk of hidden damage from accidental water leaks could lead to moisture collecting around the panel.

Above horizontal DPC level

  • All exposed end grain to the wall panel must be suitably treated (e.g. end grain edges of the panel or where holes are cut through the panel to form openings – windows, doors, flues etc.) The end grain sealant should extend 50mm onto the panel sides.
  • There must be a drained and vented cavity with a minimum 50mm residual cavity retained.
  • The external wall insulation must be a ‘breathable’ type insulation and directly fixed to the CLT wall panel.
  • An approved breathable membrane must be installed to protect the insulation on the cavity side.
  • Suitable approved wall ties must be used which are secured to the CLT panel.
  • The CLT panels should be protected on the ‘Warm side’ by a suitable vapour control layer (vcl) unless interstitial condensation risk analysis calculations prove that the risk of interstitial condensation will not occur within the construction.
  • The structural engineer must provide details of suitable mechanical fixings to secure the CLT panels to the substructure.

Generally

  • The project using CLT panels must be supported by full structural design specifications.
  • General construction should follow the guidance contained within Timber frame section of the Technical Manual.
  • Detailing for Gas membranes must be considered on a project by project basis and you should consult with our Warranty Surveyor for further advice.
For more information please visit www.premierguarantee.com.
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The Flint Walls of Dover

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.

For more information please visit www.milbank.co.uk
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A Standard for Change

In February, schoolchildren from around the globe went on strike to demand urgent action on climate change. It followed stark warnings within a report from the Intergovernmental Panel on Climate Change (IPCC) stating that unprecedented measures are required within the next 12 years to limit temperature rises to 1.5°C above pre-industrial times – avoiding potentially catastrophic global impacts.

With the built environment estimated to account for around 40% of total UK carbon emissions1, improving the energy efficiency of our buildings must be viewed as a priority.

The Passivhaus Standard offers a proven model for minimising the energy usage of buildings via a fabric-first approach. By applying its principals with the precise design, improved predictability and outstanding thermal performance of structural insulated panels (SIPs), developers are now achieving Passivhaus Certification on projects of increasing scale and complexity.

Getting Certified

At its core, the Passivhaus Standard aims to allow the creation of buildings which require very little energy to heat or cool, whilst also providing a high level of comfort for occupants. To achieve this, it sets clear energy performance targets which a building must meet:

  • Primary energy demand ≤ 120 kWh/m2/yr
  • Space heating/cooling demand ≤ 15 kWh/m2/yr
  • Specific cooling load ≤ 10 W/m2
  • Passivhaus performance targets for cooler climate buildings

To put these figures in context, the maximum space heating demand for a Passivhaus building is around 10% of that of an average home (estimated to be 140 kWh/m2/yr 2). As such, whilst these criteria do not specifically address a building’s carbon emissions, in practice they should significantly limit emissions when compared with a property built to current Building Regulations/Standards.

To meet these criteria, all areas of the external fabric of the property typically need to be insulated to a U-value of 0.15 W/m2.K, or lower. It is also a requirement of Passivhaus that the building be fundamentally ‘thermal bridge free’. To achieve this, close attention to detailing is crucial when designing the building and installing the insulation to ensure that potential thermal bridges around openings and at junctions (especially the wall / floor) are properly addressed. In addition, air leakage rates must be no higher than 0.6 ach@50 Pa. This is typically achieved by installing an airtight layer, such as oriented strand board (OSB), and airtight tape, which is applied to seal all junctions.

High levels of airtightness within Passivhaus buildings necessitates good ventilation via means of a mechanical ventilation with heat recovery (MVHR) system. MVHR systems extract the heat from outgoing stale air and transfer it to warm incoming fresh air, further reducing the heating demand and ensuring a fresh, comfortable environment within the home.

Whilst it is possible to attain Passivhaus certification with traditional construction methods, in many cases offsite construction approaches such as SIPs can provide a simpler, faster and more adaptable solution to meeting the demanding fabric requirements.

SIPs

A typical SIP comprises an insulated core sandwiched between two layers of oriented strand board (OSB), with a jointing system that ensures excellent insulation continuity throughout the envelope, limiting repeating thermal bridging. The panels are precision cut to each project’s particular specifications in a production facility, including spaces for openings, such as windows and doors. This ensures an accurate fit, significantly reducing the need for onsite adjustments and waste. It also gives architects considerable freedom in determining the design for the property.

The panels offer excellent ‘out-of-the-box’ fabric performance with whole wall and roof U-values of 0.20 – 0.17 W/m2.K, or better. By assessing all junctions and openings within the building envelope, and carefully installing additional insulation, thermal bridges can be eliminated, and the U-values of all elements reduced to the required level.

The jointing arrangements inherent in SIPs can also support extremely airtight structures. Once an airtight membrane is fitted internally and tape is applied to junctions, the air leakage rate can be reduced to the 0.6 ach @ 50 Pa required by the Passivhaus Standard.

SIPs also provide a number of practical benefits. Their offsite production process supports greater predictability in scheduling, allowing project teams to accurately plan for panel deliveries, avoiding trade overlaps and maximising site efficiency.

The panels can be quickly installed by a small team of trained operatives with a dry construction process that is less dependent on weather conditions than other traditional approaches. When SIPs are used for both the walls and roof, the outer shell of domestic properties can often be erected in just two to three weeks. With the addition of a breather membrane to the panel exteriors, the construction is made weathertight — allowing internal fit-out to begin. The outer timber facing also provides a suitable substrate for a variety of cladding options including brick slips, render and timber cladding.

In Practice

One project to take advantage of the benefits SIPs provide is the Norwich Regeneration Company’s Rayne Park estate. The development includes a mix of private and affordable housing, with 112 of the 172 properties, earmarked for full Passivhaus Certification.

The Kingspan TEK Building System was chosen to form the envelope of many of the dwellings based on its technical specification and value offered through its offsite production process. The first phase of the development completed this March, with the Passivhaus units expected to have a heating demand of just 11 kWh/m2/yr and a primary energy requirement of 77 kWh/m2/yr.

Scalable Solution

With over 65,000 buildings now certified Passivhaus around the globe, the Standard provides a clear route to dramatically reducing the energy performance, and consequently carbon emissions, from our buildings. Offsite approaches such as SIPs provide the ideal delivery method for this standard, allowing the cost-effective construction of entire estates.

For more information please visit www.kingspaninsulation.co.uk
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Hybrid precast concrete the best of both worlds

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!

For more information please visit www.kerkstoel.be/en
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James Jones in partnership with Ockwells

James Jones Timber Systems Division forms partnership with Ockwells to offer stairwell protection systems to UK housebuilders.

James Jones & Sons’ Timber Systems Division, the maker of the UK’s market-leading I-Joist system, JJI-Joists, has entered into a partnership with specialist building and protection materials manufacturer Ockwells, which will see it recommending Ockwells’ Stairwell Hatch System to all JJI-Joist customers in the future.

After months of research in to available stairwell protection systems, James Jones’ Timber Systems Division has opted to recommend the Ockwells temporary site protection system because of its superior build quality, flexibility in applications of use and the simplicity of installing the system to house building and construction sites without adaptation to existing build practices.
Independently tested and verified, the Ockwells Stairwell Hatch System is designed to provide full cover platforms over the stairwell openings in various combinations to suit all build sites and conditions. Once installed, the system prevents falls through large stairwell opening whilst giving access for operatives and materials.

The system is designed to be lightweight for handling and ease of use on site and it allows safe and fixed access to a ladder prior to a staircase being fitted. The system comprises three parts – hinged and framed glass reinforced plastic (GRP), a steel ladder plate for securing a ladder and a steel box sections adjustable telescopic joist, which allows openings next to party walls to be accommodated by the system.

Speaking of the joint venture Mark Tilston, Systems Development Manager for James Jones’ Timber Systems Division, said “Stairwell protection systems is something that our business has been investigating and researching for a while now and we are delighted to have found in Ockwells a partner that provides a robust and safe solution for all JJI-Joist distributors and end users.
“The Stairwell Hatch System is well designed, solidly manufactured and above all, it works. They have also produced a simple step by step installation guide which gives you clear advice on many applications. The system allows you to continue using crash deck systems and bird cage platforms which is unique. Their product has been independently tested to give you confidence.”

John Gray, Sales Director at Ockwells, said “Ockwells are delighted to be partnering with James Jones’ in this new and exciting development. Having spent a great deal of time developing the Stairwell Hatch System it’s great to see that our customers are seeing the benefits from our safety system.

“As well as providing a safe working platform over stairwell openings, the Stairwell Hatch System is also very cost-effective, being reusable means that the initial investment is quickly recouped when compared to the cost of using sacrificial joists, which can run into hundreds of pounds per plot. We believe that the combined expertise of James Jones’ and Ockwells will result in significant health and safety, and cost benefits to James Jones’ customers.”

For more information please visit www.jamesjones.co.uk.
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Creagh provide the solution for 2 new student accommodations

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.”

for more information please visit www.creaghconcrete.co.uk.
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New thinking for modular sector

As one of the UK’s largest off-site manufacturing businesses, Caledonian knows a thing or two about modular buildings. It’s one of the reasons why the company has grown to a turnover in excess of £50m and with a goal firmly set on doubling this over the next 2 years you get the distinct impression they’re set to change how the industry works. Having been founded over 50 years’ ago and now operating from a 40-acre site in Newark, Nottinghamshire, they’re unusual in having one of the longest trading histories in the modular sector.

Success has come about by sticking to what it does best; high quality modular accommodation that is delivered to site with up to 96% of the build completed in its quality assessed manufacturing facility. Proof is in the pudding and they don’t get much bigger than the £53m Hinkley Point C worker accommodation contract that was successfully delivered in 2018. Effectively creating in ‘new town’ in just 51 weeks, it shows the capability of modular construction and how, if the government’s rhetoric on solving the UK’s housing crisis once and for all translates into action, Hinkley is the shape of things to come. Housing providers should take note of what Caledonian has achieved – effectively creating a modular new town at Hinkley that houses 1,496 workers in just 51 weeks.

Caledonian’s innovative modular building system means that programme savings of up to 50% or more are possible compared with traditional forms of construction. And the programme can be more predictable than when using conventional methods as well as reducing waste and number of deliveries to site.

Project delivery

A central pillar to the company’s growth is the ongoing focus on quality and project delivery. The underpinning methodology is to take a traditionally constructed building and apply latest manufacturing techniques to drive efficiencies. The three core areas of this are the use of BIM, design for manufacturing and assembly (DfMA) and lean manufacturing techniques.

The results are replicable, too. The latest is a £25m project that involves Caledonian working with Bowmer & Kirkland to manufacture high quality student accommodation as part of a £54m development for the University Campus of Football Business, First Way Campus in Wembley.

The 680 bedrooms will be manufactured and installed by Caledonian and, similar to Hinkley, will be 96% complete prior to shipping to site. That was one of the main reasons they were selected for this project; because they could show how the modules would help meet the strict deadline dates, which required handover by July 2020 in time for Euro 2020. First Way Campus is situated a few minutes’ walk from Wembley Stadium, and will include a mix of purpose-built student accommodation as well as academic, office and outdoor space.

Fire compliance capabilities of the modular system also featured highly in the selection process, due to the high rise nature of the development. It rises to 11 storeys and that really shows what is possible with the company’s modular building solution. Caledonian gave the client and design team confidence post Grenfell, providing a pre-engineered fire compliant modular solution suitable for a development of this scale.

Damian Flood, CEO of Cole Waterhouse, said “We liked the modular building solution proposed by Bowmer + Kirkland and its supply partner Caledonian for First Way Campus because it was a practical way of meeting the strict schedule. We are providing Wembley and the UCFB students with a fantastic campus that will include a number of facilities for students including purpose built accommodation (678 beds), seminar rooms and staff office spaces as well as amenities such as a café style restaurant, a gym and library/IT suite.”

Developers Cole Waterhouse brokered a deal with Unite Students, a leading provider of student accommodation in the UK. Caledonian has incorporated the Unite requirements into the design to provide a higher standard student living experience than is traditionally expected.

Modular Mindset

Caledonian is a company with an eye firmly set on the future and as Chief Executive Officer Paul Lang explains: “Our ability to deliver to a strict schedule and have an existing fire compliant solution made a compelling proposition for First Way Campus. We are able to achieve consistent project delivery by investing in BIM, design for manufacturing and assembly (DfMA) and lean manufacturing. In combination we believe that it will help us raise industry standards across the board. Our long term goal is to lead change in the industry by establishing a ‘modular mindset’ with clients and developers.”

For more information on Caledonian modular buildings and offsite construction solutions, visit: www.caledonianmodular.com
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Offsite reaches new heights in Birmingham

A two-block 22 storey residential building topped out last month on the site of an old subterranean car park in Birmingham. Joe Bradbury was in attendance at the event, which proved to be a milestone for Creagh Concrete and a testament to the true power of offsite manufacture.

Standing on top of a 22 storey building in the middle of a city I hold dear was something I am unlikely to forget. As Editor of Building Specifier and regular contributor to trade publications within the construction industry, offsite construction is something I get to write about on a regular basis. But to actually stand on top of a tower block that was built using such practices brought with it a profound sense of what we are capable of as an industry when we set ourselves ambitious targets and knuckle down to achieve them.

Project overview

The two blocks house 323 apartments and have been built in a major contract by housing giant Galliford Try. The £40m project is part of a build-to-rent scheme for client Dandara Living, one that is expected to significantly boost the number of homes available in close proximity to Birmingham’s city centre once completed. Comprising two blocks of 17 and 22 storeys linked by bridges at each level, the development will feature studio, one-bed and two-bed apartments with balconies across all elevations.

The towers are the tallest structure completed by Creagh across their entire 43-year history; and as a proud Midlander and lover of Brum, I would pose the question: where better for such a feat to proudly stand than beside the existing Alpha Tower, a Grade II-listed office built in the 1970s, considered one of Birmingham’s most well-known architectural landmarks?

Offsite manufacture

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. With this in mind, the project team looked at various different options for the structure and its subcontractors, before settling on the team at Creagh Concrete to deliver and install the frame panels, cladding sections, balconies and floor slab.

Galliford Try Project Director Aidan Smith said “We knew we wanted the robustness that precast concrete offers and spent a lot of time researching our subcontractors. Creagh has the capability and experience to deliver both the hollowcore floor slab and the architectural precast concrete that we wanted. The screed that we place on top of the floor slab is there just to iron out any changes in level. It gives us a little wriggle room.”

The placing of each level is based on a turnaround time of just 10 days. Prefabricated bathroom pods, manufactured in Hull, are lifted directly into position at each level as part of the cycle time therefore it was important that these were delivered between days five to seven – any later runs the risk of disrupting the project programme.

With a turnaround time of just 10 days to place each level, the Galliford Try team is running the internal following trades just three floors behind.

In conclusion

The speed and efficiency of construction displayed with this project creates a real sense of momentum that I personally could feel when walking up the tower and standing on the top. Things are getting done fast and they’re getting done right. If works continue at such rapid pace, it would come as no surprise if the team hit their handover date of May 2019 with room to spare. (Remove)

Creagh Director and Co-Founder Seamus McKeague concluded “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.”

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Stratford’s City Mill Lock Island transformed by new energy efficient Cross Laminated Timber homes

City Mill Lock Island – a small man-made structure housing a working lock on the Bow Back Waters at Stratford, has been transformed by a new residential development designed and delivered by Architect and Developer Roberts & Treguer. Known as Blaker Island, the development is formed of two new Cross Laminated Timber (CLT) buildings built either side of a Listed and refurbished 1930’s lock keepers house. The two new buildings, Howards House and The Warehouse – a five storey apartment block, have been designed to passivhaus standard and provide seven spacious, modern homes with views over the Olympic Park and surrounding waterways.

The new buildings are built from Stora Enso PEFC certified Cross Laminated Timber which has helped to meet the high level of airtightness required for Passivhaus. Other key considerations for the specification of CLT include its ability to resolve limitations presented by the island site in terms of weight and access, possible only via a small foot bridge. Specialist hybrid construction firm, G-frame Structures, who supplied and installed the CLT, devised an innovative installation strategy to overcome the complex site logistics which enabled them to safely and efficiently deliver both superstructures in just six weeks.

Roberts and Treguer’s design concept for the development was driven by a desire to provide high quality, low energy homes that would be completely different to anything else available in the area. “From the outset a key part of our design intent was to build highly sustainable and energy efficient homes that would meet passivhaus standards and CLT has helped us to achieve this due to its high airtightness qualities.” Explains Bachir Nebia, Contracts Manager at Roberts & Treguer.

Airtightness details for Howard’s House and the Warehouse are designed to 0.6 ACH (air change) which is the maximum allowed for achieving Passivhaus standard. Windows are triple glazed and junction detailing between window and CLT wall panels has been carefully considered. Energy efficiency is further improved by a compact unit in each dwelling which combines MVHR with an air source heat pump to provide ventilation, heating and hot water. It is estimated that over a 60 year period a typical dwelling will save 192 tonnes of CO2 compared with a typical UK home.

Weight was also a key consideration in the specification of CLT: “We were going to be adding a lot of weight to an existing structure and this was a key factor in the material specification. The island has river walls all around it which are owned by the Canal Trust and we carefully considered the potential impact on them of increased weight.” Says Bachir.

“CLT is a more lightweight structural material than traditional construction materials and this enabled the project team to reduce the weight of the superstructure while still creating spacious, sustainable and energy efficient homes. We worked closely with G-frame Structures and timber engineer Furness Partnership on the detail design and the G-frame team developed quick and efficient solutions for the crane and installation strategy.” He continues.

Lee Murphy, Managing Director of G-frame Structures expands on this: “The site is a man-made island surrounded by water on all sides and this made other, more traditional methods of construction less feasible. In terms of overcoming such complex site constraints, CLT provided the perfect solution because it is lightweight, fast and efficient. The installation strategy we developed involved the erection of a 100 tonne mobile crane adjacent to the site which we used to lift in a self-erecting IGO50 mini tower crane to the island. This enabled the G-frame team to safely, quickly and efficiently install Howard House and the Warehouse apartments in a very short timeframe.”

These factors were key considerations for the structural design and CLT panels were specified to be liftable by the IG050 mini crane. Brick slip cladding further contributed to achieving a lighter overall weight for the buildings as well as allowing for walls to be formed from the CLT wall panel, insulation and cladding without dramatically increasing thickness.

The site layout also required the development of a cantilevered section at the corner of the Warehouse building to avoid the foundations of the foot bridge which are located close by. This was resolved by the introduction of Glulam beams integrated to the open façade and incorporating step-in level access to the bridge for servicing the building.

Sound separation at the Warehouse was achieved by the use of double-layer CLT walls around the full height central core which houses the lift shaft and staircase. The two walls are separated by only a 90 mm space and to overcome the inaccessible nature of this element of construction, G-frame Structures used discreet connections which also contributed to the overall aesthetic of the building.

Externally the development presents a varied streetscape and Roberts & Treguer have taken care to reflect the history of the Island and surrounding waterways. Though having the external appearance of one single house, Howard’s House is comprised of two spacious three bedroom homes. The design is based on the original home of the 19th Century chemist and amateur meteorologist Luke Howard which was originally situated on the island but demolished in 1934. Howard is known as the ‘Namer of Clouds’ for having developed the nomenclature system for cloud classification which is still used today.

Inspiration for the adjacent five storey block of flats, known as The Warehouse, is taken from the local vernacular of traditional warehouses to be found on the rivers and canals of Stratford.

The Warehouse is very generously proportioned with just one three bedroom apartment on each of the ground, first and second floors and a two bedroom penthouse on the third and fourth floors.

Bedrooms and large open plan kitchen/living spaces lead from a central hallway where the MVHR unit is located so that humid air can be extracted from the kitchen and bathroom and fresh air supplied to the bedrooms. The building features a recessed roof garden which has been achieved by an innovative solution developed by G-frame Structures and Furness Partnership whereby the beams effectively act as a cradle for the floor which hangs beneath.

Internally, all the new homes feature exposed CLT throughout with accent provided by a simple monochrome palette which contrasts well with the texture and colour of the wood. All homes on Blaker Island were sold on first viewing.

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Offsite construction is here to stay

Recent press coverage has focused heavily on Offsite Construction providing the answer in a number of key sectors, due to the speed and efficiency of modular construction.

Premier Modular has been delivering award winning offsite and volumetric solutions for more than 60 years and prides itself on its ability to provide the highest quality buildings, offering a skilled and knowledgeable design and build service. Part of a large multi-national industrial group, Waco International, Premier has the strong financial backing provided by the Group, which has enabled it to build a substantial modular hire fleet. This coupled with the manufacturing capacity offered by a 22 acre site means that Premier is ideally suited to deliver quality buildings for both hire and sale throughout the UK, no matter how large or small.

Premier’s ability to deliver a modular solution on a massive scale is evidenced by the series of modular complexes they have provided at Hinkley Point C in Somerset. The buildings deliver 38,000 sqm of offices and welfare facilities to house all the management and technical personnel required for the construction phase of the new nuclear power station. The HPC requirement for the best temporary welfare and office facilities in the UK, delivered within a strict timescale, was a challenge Premier met and achieved and resulted in their being appointed to deliver an additional modular complex for the critically important infrastructure project.

Developing such strong client relationships is at the core of Premier’s approach and their recent partnership with ISG Construction has delivered 8 school facilities in 12 months as part of Manchester City Council’s Education Basic Needs framework. The first school, St Margaret’s CofE Primary School, was chosen by Manchester City Council to be their first pilot for delivering a project to BIM Level 2, including their first Asset Information Model. The 775m2 2-storey building provided new nursery facilities and 3 reception classrooms, enabling the school to expand and accommodate an additional form of entry. This scheme was named as the winner of the Digital Construction category in the North West Regional Construction Awards for 2018, as well as receiving Highly Commended in the Integration and Collaborative Working category.

Standardisation in construction delivery produces better end product quality, reduction in manufacturing costs, reduced design costs with less waste and can be achieved through the use of standardised components, prefabricated panels and modular construction.

This volumetric approach to construction was used in the award winning construction of a 5 storey student accommodation block, The Foundry, in Newcastle City Centre, delivered in partnership with Sir Robert McAlpine. This block consisted of a mixture of 54 studio flats, 105 ensuite bedrooms and 2 accessible rooms, associated living spaces, kitchens and study areas.

The speed of delivery for this project gave the investors a whole year of additional return and was a deciding factor in the project being named as the Project of the Year (up to £10m) at the Construction News Awards.

This approach has also been used to great effect in other residential projects and following their appointment to the CHIC BuildSmart framework, Premier have worked closely with their framework partners to develop standardised housing products, delivered within an EU-compliant framework – the perfect solution to the critically important delivery of housing stock highlighted frequently in the news.
The standard designs, coupled with CHIC’s existing proven materials supply chain, has resulted in a more cost efficient, quality product, with speed of delivery. Whilst the cost benefits of this scheme have been delivered by the development of a standardised product, flexibility is still available to procure bespoke designs and solutions where required.

Premier’s forward thinking attitude means that they are always looking for product improvements and innovation; Premier believes that the fire resistance of buildings is very important, whether for a temporary or permanent building. At Premier we feel it is not good enough to provide our clients with an assumption that our buildings are ‘fire proof’ based on various codes and data sheets. When developing our latest product, as part of our quality control during development, we ensured the product went through real life fire tests and received certification for this.

In a market where shortages exist, building standards are extremely high and sustainability is of growing importance, standardisation and offsite construction as delivered by Premier has to be a big part of the solution.

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