Latest innovations and products in the offsite sections of the construction industry.

Protect Membranes installed in award winning education project

A combination of Protect construction membranes has been supplied and installed at Glasdir School, a modern school building constructed to BREEAM Excellent standards using BIM Level 2.

Built by Wynne Construction and designed by architects Lovelock Mitchell, this £10.5 million project involved re-locating two primary schools to a brand new shared site in Ruthin, delivering a complete solution to client Denbighshire County Council as part of the Welsh Government’s 21st Century Schools and Education Programme.

Manufactured offsite by construction specialist Innovaré using their advanced i-SIP technology, an independently accredited Structural Insulated Panel System (SIP), the resulting structure was both water and airtight, delivering thermal efficiency to a final U-value of 0.15w/m2k. The structure led to Innovare being the winners of the Best Use of SIPs category at the 2018 Structural Timber Awards.

Protect’s TF200 external breather membrane was used externally on the SIP to ensure high water resistance and vapour permeability, minimising the risk of interstitial condensation in the wall structure. Internally, Protect BarriAir was used to ensure the integrity of airtightness and to significantly reduce heat loss and air leakage through the building fabric.

Craig Lee, Supply Chain Manager at Innovaré commented “Over 10,000m2 of i-SIP components including internal and external walls and roof cassettes were erected by Innovare in only 13 weeks, 55% faster than traditional build. By using Protect’s membranes we have peace of mind, both in long term performance as well as timely deliveries, which helped us to maximise the speed benefits of offsite construction.”

For details of how Protect products can be incorporated into residential and commercial builds, please visit www.protectmembranes.com, email info@protectmembranes.com or call 0161 905 5700, quoting ‘Glasdir School.’

Images courtesy of Wynne Construction

For more information please visit www.protectmembranes.com.
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Managing heat, air and moisture movement in modular buildings

For modular buildings to be energy efficient, healthy, and moisture free what is required is a holistic approach to a total system which manages the balance of Heat, Air, Moisture Movement (HAMM), considering an integrated approach to airtightness, insulation and condensation control.

Buildings with very low rates of air leakage require correspondingly higher levels of ventilation as part of a balanced, design approach. It’s important to bear in mind that ventilation is controllable, and therefore can be accounted for within the overall design, whereas uncontrolled air leakage is not.

The incorrect specification or installation of effective thermal barriers will lead to unmanaged heat loss, impacting directly on the energy efficiency of the building and its systems.

Airtightness and vapour permeability

Air movement is important in the building envelope both infiltration and escape. We need to control interior conditioned air (whether heated or cooled) escaping and exterior air infiltrating that puts more pressure on heating or cooling mechanisms internally. Airtight membranes are key in this area whether vapour and air open/closed or variable.

Moisture vapour will pass through the various layers of any construction by both convection and diffusion. The objective is to ensure, by design, that the moisture vapour can disperse to the outside atmosphere without being cooled to below dewpoint temperature, thus eliminating condensation and associated problems such as mould growth.

To avoid the occurrence of excess condensation, which can result in mould growth and damage to the building fabric, designers should assess the amount of water vapour likely to be generated within the building and determine the resultant increase in internal vapour pressure above that of external air. They should then consider the physical properties of the construction separating inside from outside.

Why airtightness is crucial to modular building design

There is absolutely no question that an integral part of modern building design is influenced by energy efficiency. In the EU it is estimated that buildings account for approximately 40% of energy consumption and are responsible for some 36% of CO2 emissions. Closer to home, around 45% of UK CO2 emissions come from the built environment, (27% from domestic dwellings and 18% from non-domestic).

Airtightness improves energy efficiency

As thermal insulation requirements have increased over the last few years, the proportion of energy lost through air leakage has become more evident. The ever-increasing thermal insulation required will, however, be rendered largely ineffective unless the airtightness of the structure itself is addressed. Air leakage greatly reduces the effect of thermal insulation; therefore if energy efficiency is to be improved within buildings, this is the most critical area to focus on.

In addition to improved insulation, energy efficient heating systems will also be ineffective if warm air can escape the building and cold air can seep in. This is reflected in the fact that total space heating costs in an airtight construction may be considerably less than in a leaky one.

Air leakage through cracks, gaps, holes and improperly sealed elements such as doors and windows can cause a significant reduction in the performance of even thermally insulated envelopes. Architects are increasingly turning to air barrier membranes as an essential part of the design process in achieving the most effective means of controlling and reducing air leaks.

In terms of the energy efficiency of a building, uncontrolled air flow will almost certainly have a major impact. Initial heat load calculations for heating and cooling equipment will usually make an allowance for a level of natural infiltration or uncontrolled air flow. The higher the infiltration rate, the lower the energy efficiency of the building. Efficiency levels can be affected by both natural and mechanical air movements. The forces of wind and stack effects will lead to a level of air infiltration and subsequent efficiency loss. Sealing the shell of the building and any un-designed holes can reduce the impact of wind and stack effects and improve the overall energy efficiency.

Airtightness protects building fabric and reduces maintenance costs

Unmanaged or uncontrolled air flow will act as a carrier for moist air, drawing it from outside in, or pulling it from inside out, into walls, ceilings, and roofs. The impact of uncontrolled moist air movement can have a long-term detrimental effect on the durability and life of the building. This, in turn, can lead to:

  • Decay of organic materials such as timber frames
  • Saturation of insulating materials, thus reducing their insulative effect (further increasing heat loss)
  • Corrosion of metal components
  • Frost damage where moisture has accumulated on the cold side of the insulation

The design of an effective airtight system will reduce the risk of uncontrolled moisture movement, and the potential for damage caused by condensation within the building fabric.

Effective airtightness design

The two main ways to achieve airtightness in the building envelope are internally or externally, or in other terms, ‘inside of the services zone’ or ‘outside of the services zone’.

Traditional use of internal air barriers can be more complex and costly to install, due to the need to accommodate building services such as electrical, lighting, heating and drainage systems. An internal air barrier is only as good as its installation. If all the service penetrations are not adequately sealed, performance will be compromised.

For many years, external air barriers have been commonly specified in North American building design and construction. By moving the air barrier to the external side of the structural frame, external air barrier systems such as Wraptite from A. Proctor Group allow for an almost penetration-free airtight layer, which can be installed faster and more robustly. This offers an effective but simple system comprising a self-adhesive vapour permeable air barrier membrane, plus vapour permeable sealing tape, Wraptite Corners and Wraptite Liquid Flashing, and provides effective secondary weather protection while preventing trapped moisture and air leakage. Far simpler than internal options an external air barrier system like Wraptite will maintain the envelope’s integrity, with less building services and structural penetrations to be sealed, and less room for error.

Incorporating Wraptite in the design makes sense

Wraptite is a patented external air barrier membrane system, which offers manufacturers and designers of modular and off-site buildings the ability to reliably and comfortably exceed current airtightness requirements. Wraptite is the only self-adhering vapour permeable air barrier certified by the BBA and combines the important properties of vapour permeability and airtightness in one self-adhering membrane. This approach saves on both the labour and material costs associated with achieving the demands of energy efficiency in buildings.

  • Complies with use on buildings of high rise and over 18m under Part B amendments made in November 2018, Membranes need to be Class B,s3,d0 or better, with Wraptite at Class B,s1,d0*
  • Included within BS8414 testing with cladding manufacturers
  • EPDM not needed to the frame of the building as Wraptite is self-adhesive and continues across the whole envelope of the building against the sheathing board and the frame of the building
  • Less EPDM around window details due to Wraptite lapping into the building at junctions
  • Corner detailing for opening and movement joint interfaces are easily treated
  • Improved airtightness and may negate the use of a VCL totally from the design internally, meaning easier a quicker install of dry lining package
  • Hydro-Thermal Modelling (WUFI) showing the difference of not using a VCL within some constructions benefits the building further
  • Improving airtightness may allow you to change thickness or type of insulation used when modelled through SAP or SBEM
  • No need to tape sheathing boards as Wraptite is positioned across the whole board
  • Testing has seen results as low as 0.5 m3/(h.m2) @ 50PA carried out at Windtech on a window façade panel
  • By using Wraptite on the external, this may show you an improvement on making the building watertight, allowing your cladding package to come off the critical path and internal works to start earlier, and also internal works may not be installing a VCL so the site program is potentially quicker

High-performance off-site solutions

The A. Proctor Group Ltd has been providing solutions and products to the construction industry for over 50 years. The company has been developing vapour permeable membranes and vapour control layers for over 25 years, and provides an extensive range of superior high-performance products suitable for modular and off-site construction.

Dedicated in its approach to helping you to achieve best practice, effective and reliable solutions to meet your modular building requirements in line with building regulations and energy efficiency, the A. Proctor Group team of highly experienced industry professionals and technical advisors is on at hand to guide you and support you from design throughout the construction process.

The A. Proctor Group range of products include unique off-site solutions for the following sectors:

  • Private and social/affordable housing
  • Purpose built student accommodation
  • Self-build projects
  • Hotels
  • Education buildings
  • Healthcare including hospitals, health centres and healthcare facilities

*tested over 12mm calcium silicate board / fibre cement board as per BS EN 13238:2010. All tests carried out to EN 13859-2 standard.

IMAGE courtesy of Kingspan TEK

For more information please visit www.proctorgroup.com.
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A lesson in acoustic control in education

With research highlighting that ineffective sound control has a lasting negative impact on education performance , it’s an ideal time for those involved in the education build sector to reflect on whether they are implementing adequate acoustic control to ensure building compliance in accordance with BB93. Here Rodney Davidson, Head of Specifications at AG looks at current standards and highlights Cheltenham Ladies College where AG’s Alphacrete® Acoustic masonry was used to create an aesthetically pleasing, calm, safe and health-promoting space.

Acoustic control: Why it’s important

The link between ineffective noise control and a poor education performance affects those involved in the Education build sector two-fold. Firstly, careful consideration should be given as to whether the correct building products to control external noise pollution and safeguard the health and wellbeing of the school’s surrounding community and local residents have been used. For example, a gymnasium housing a loud basketball game with cheering crowds should not be heard in nearby classrooms where lessons are taking place. Beyond the obvious distraction to students, proven hormonal responses to loud, unpredictable sounds suggests that students exposed to chronic loud noises over time are at risk of damage to their general health and mental wellbeing, not to mention academic performance.

Secondly, consideration should be given as to whether the correct building products have been specified to instil adequate reverberation time control within each particular room or space. Without appropriate acoustic control measures in place large unfurnished areas like sports halls or assembly halls will have extremely long reverberation times; in layman’s terms this means that the room will have a lot of echo and it will be difficult to hear and understand speech or music within that space which is not at all ideal for students in a learning environment.

What are the current standards?

BB93: February 2015 sets out, minimum performance standards for acoustic requirements of school buildings. The overall objective of the performance standard is to ensure that the design and construction of school buildings provide acoustic conditions that enable effective teaching and learning.

All parties involved in the build have a responsibility to ensure the products used successfully help to control reverberation time and meet the performance standard set out in section 1.5 table six of BB93: 2015.

Achieving the right reverberation characteristics is critical to the acoustic performance of an interior space, particularly in school buildings. Good acoustics reduce distraction from airborne noises and make it easier to hear people speak, which is critical in a learning environment and helps aid and enhance pupils’ learning capabilities.
Acoustic control in action

AG completed the impressive gymnasium at the Cheltenham Ladies College in Gloucestershire using AG’s Alphacrete® acoustic block range; providing structural support and optimumal light reflectance value (LRV) for sports halls according to Sport England’s guidance.

The low-maintenance blocks arrived on site in the chosen colour (Ernestone Buff) negating the need for painting or adding a protective sealant, and were built below wooden panelling at Cheltenham Ladies College to create a distinctive contrasting aesthetic that was practical too. Alphacrete® acoustic block’s durable surface made the hall hard-wearing against knocks, bangs and wayward balls, whilst also absorbing sound efficiently.

The brief included the need for a brand-new wall mounted basketball and netball nets. Sports equipment, door frames and window sets are all easily integrated with Alaphacrete® acoustic when installed in line with AG’s design guidelines.

Alphacrete® acoustic blocks are compatible with a wide range or mortar blends. For this particular project M4 Medium Buff mortar was used as supplied by CPI Mortars.

Peace of mind with Alphacrete

Design and build contractors and Specifiers can now have the BB93 reverberation time compliance confirmed prior to construction when AG’s Alphacrete Acoustic range is used, negating the need for post construction testing. For more details contact AG’s specification team at specifications@ag.uk.com or visit www.ag.uk.com.
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Protect Membranes delivers U-value benefits for new modular innovation

A variety of wall construction membranes, roofing underlays and accessories from Protect has been installed into an innovative new modular concept manufactured by Tingdene Homes, holiday and park home specialists.

Offered under the THL Modular branding, The Loft is a contemporary two-storey holiday home designed and manufactured completely offsite in Tingdene Homes’ factory, using cutting edge design and high end specification to meet the needs of the growing “staycation” market. Fully LABC product approved and constructed to UK Building Regulations, The Loft can be built to suit varied client needs ranging from a two or three bedroom luxury lodge to a two or four room hotel pod, club house or café. A number of Protect products were supplied and installed on THL Modular’s first show home, including Protect BarriAir, an internal airtightness membrane, Protect VC Foil Ultra used as the insulating low emissivity vapour control layer, Protect TF200 Thermo insulating low emissivity breather membrane for external walls and Protect VP400 Plus LR, a roofing underlay offering unrestricted wind uplift resistance, and exceptional vapour permeability.

Phil Harold, Quality Assurance Manager at Tingdene Homes commented “The use of numerous Protect products for this development helped us meet specification and achieve our target U-values of 0.18 W/m2K for external walls and 0.14W.m2K for the roof element. With the numerous benefits of offsite manufacture over traditional construction including build speed, quality precision and reliability, we wanted a supplier who understood these principles to ensure our delivery demands were met. Protect supplied products quickly which enabled our process to run without interruption and facilitated swift turnaround at the factory.”

Protect’s range of wall, ceiling and floor construction membranes together with its roofing underlays and accessories provides a comprehensive solution to the modular build sector. In particular, Protect construction membrane products with reflective technology help deliver thermal efficiency benefits to meet low target U-values and ensure compliance with relevant Building Regulations.

For details of how Protect products can be incorporated into residential and commercial builds, please visit www.protectmembranes.com, email info@protectmembranes.com or call 0161 905 5700, quoting ‘The Loft.’
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Lindapter launches new modular booklet at the Offsite Construction Show

Since 1934 Lindapter has pioneered the design and manufacture of steel connections that eliminate the need for welding or drilling on site. Whether securing structural steel sections, cable management systems or constructing modular buildings, Lindapter has a proven, accredited and adjustable connection that will allow fast alignment during construction.

The adjustability of Lindapter’s clamping systems is particularly beneficial to contractors working in the modular or offsite industry because it allows them to maximise efficiencies and control costs. For example, cable managements systems contain several components that need to be positioned correctly as fast as possible.

Lindapter’s Girder Clamps allow contractors to loosely fasten the cable tray modules into position before aligning into position and tightening the clamps with standard hand tools to complete the installation. Girder Clamp by Lindapter also allows for a convenient disassembly or removal for maintenance, while preserving the integrity of the steelwork.

Hollo-Bolt by Lindapter is also used extensively in the modular construction industry. A recent example is The Spurn Discovery Centre in East Yorkshire where Hollo-Bolts were used to connect the Structural Hollow Section (SHS) frameworks of the rooms together.

The Hollo-Bolt was selected because of its high strength capacity and its range of independent technical accreditations, including the CE Mark and the ICC-ES seismic approval for resisting wind loads in all seismic design categories.

The Hollo-Bolt allowed a fast and convenient installation process from the inside of the modular rooms using just standard hand tools, which resulted in an efficient construction schedule.

Find out more about Lindapter steelwork applications in the new modular and offsite construction booklet that is now available for download from www.Lindapter.com.
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Collaboration is the key to creative structural solutions

The structure of a building is integral to its success: choosing the right material and method of construction can affect everything from the finished project’s BREEAM rating to the return on investment. Getting it right from the beginning is crucial.

With potential legislation changes pending, working with a partner you can trust is just as important than the final choice of the structural frame solution. An experienced structural specialist is ideally placed to work alongside architects, main contractors and even the end client to deliver a successful scheme that meets regulations and exceeds expectations for all involved.

At B&K Structures, we have a long history of innovation to ensure that our projects will stand the rigours of time, conform to legislation, offer environmental benefits as and meet the design challenges.

Our commitment to innovation means we think beyond the structural frame, moving forward towards more frame and envelope solutions which will include full system testing from the outset ensure that our products interact with all elements of the building.

The options

Different projects call for different solutions, and we work closely with designers and our supply chain partners to deliver the correct result.

We always look for ways we can add value to projects – whether it’s reducing the load on the foundations whilst gaining additional storey heights, or maximising floor space to create airy interiors. Certain materials lend themselves to applications more than others.

Greener structures

For projects where sustainability and reducing environmental impact is a key target, engineered timber is the best option, and we remain fully behind our cross laminated timber (CLT) and glulam offering. Our timber products are fully PEFC or FSC certified, and the carbon is locked into the building rather than released to the atmosphere.

Timber is the only truly renewable construction material, and when combined with offsite construction methods, CLT’s impact on a project’s sustainability is impressive – especially where there are carbon reduction targets in place.

Using CLT as a structural material will lower the overall mass of the building, having a positive impact on foundation and piling design, reduces construction programmes and allow follow on trades to the start much sooner in the process then traditional build solutions. CLT also brings forward fewer site personnel, fewer deliveries, all helping to have a positive impact on the local community during the construction phase.

Reduced costs, reduced time on-site, and increased return on investment makes CLT a future heavyweight in residential construction.

Glulam is a structural element that is used in both vertical columns and in roofing trusses and supports. In terms of performance, it is comparable to light gauge steel frames and reinforced concrete structures whilst being, respectively, more sustainable and considerably lighter.

Where steel works

Where space and floor areas are a priority, we encourage our clients to consider steel. We have over 35 years’ experience in structural steel, so for projects which require open, airy spaces with uninterrupted square footage on the ground, we know that steel is often the best solution.

Steel structures use slim columns and large unsupported spans and are ideal for new build projects and refurbishments. What’s more, our offsite construction methods allow us to accommodate changes to the design during construction, and its lightweight nature means it can be installed quickly.

When we couple a steel frame with CLT floor decks on commercial builds, we begin to see a very compelling argument.

At B&K Structures our extensive use of BIM modelling cuts down on waste during the manufacturing of the glulam element, and our offsite construction methods with factory-controlled conditions allow us to create the glulam structural elements with minimal on-site contact.

And with the option to combine CLT or glulam with steel elements as part of a hybrid structure, we can help to control costs, create innovative solutions and improve the environmental impact and aesthetic of buildings in equal measure.

Whatever the project, we can work with our partners to devise a long-lasting structural solution that not only ticks all the boxes but safeguards the development for the future.

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Protect Membranes delivers U-value benefits for new modular innovation

A variety of wall construction membranes, roofing underlays and accessories from Protect has been installed into an innovative new modular concept manufactured by Tingdene Homes, holiday and park home specialists.

Offered under the THL Modular branding, The Loft is a contemporary two-storey holiday home designed and manufactured completely offsite in Tingdene Homes’ factory, using cutting edge design and high end specification to meet the needs of the growing “staycation” market. Fully LABC product approved and constructed to UK Building Regulations, The Loft can be built to suit varied client needs ranging from a two or three bedroom luxury lodge to a two or four room hotel pod, club house or café. A number of Protect products were supplied and installed on THL Modular’s first show home, including Protect BarriAir, an internal airtightness membrane, Protect VC Foil Ultra used as the insulating low emissivity vapour control layer, Protect TF200 Thermo insulating low emissivity breather membrane for external walls and Protect VP400 Plus LR, a roofing underlay offering unrestricted wind uplift resistance, and exceptional vapour permeability.

Phil Harold, Quality Assurance Manager at Tingdene Homes commented, “The use of numerous Protect products for this development helped us meet specification and achieve our target U-values of 0.18 W/m2K for external walls and 0.14W.m2K for the roof element. With the numerous benefits of offsite manufacture over traditional construction including build speed, quality precision and reliability, we wanted a supplier who understood these principles to ensure our delivery demands were met. Protect supplied products quickly which enabled our process to run without interruption and facilitated swift turnaround at the factory.”

Protect’s range of wall, ceiling and floor construction membranes together with its roofing underlays and accessories provides a comprehensive solution to the modular build sector. In particular, Protect construction membrane products with reflective technology help deliver thermal efficiency benefits to meet low target U-values and ensure compliance with relevant Building Regulations.

For details of how Protect products can be incorporated into residential and commercial builds, please visit www.protectmembranes.com, email info@protectmembranes.com or call 0161 905 5700, quoting ‘The Loft.’
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Raising the Bar for Offsite Construction

As one of the largest specialist off-site manufacturing businesses in the UK, Caledonian Modular offers much more than your everyday construction company. Founded over 50 years ago, they supply around the UK from a 40-acre advanced manufacturing site in Newark, Nottinghamshire.

Over the last few years’ Caledonian has achieved significant growth and now has a turnover of over £50m. A series of new contract wins look set to continue this success with a target of nearly doubling turnover by 2019, an objective they are will on the way to achieving.

Mind you, this kind of performance hasn’t come about on its own, but from a clear vision for the company, backed by a strong management team, and a focus on projects that are aligned with its key strengths and sectors that it understands; education, housing and healthcare. These include an ability to achieve up to 94 per cent completion of building modules off-site, meaning buildings can be handed over in up to half the time it takes for a traditional build, and with less disruption to roads and nearby buildings. Underlying this ability to consistently deliver projects on time and within budget is a commitment to excellence through the use of BIM, design for manufacture and assembly (DMFA) and lean manufacturing techniques.

A case in point is the £55m contract awarded to Caledonian by Laing O’Rourke to build the accommodation modules for Hinkley Point C (HPC) nuclear power station in Somerset. The contract comprises 1,496 en-suite bedrooms across 44 individual buildings at two locations. The first accommodation units rolled off the factory production line in March last year and were delivered 96% finished, ready for rapid completion. Each 34 bedroom block will be completed on site within just eight weeks from delivery. The entire HPC project is worth £18 billion across the board for the Nuclear Build programme, the largest modular government project across the entire country.

Another recent success, in partnership with their partner architects HLM, involved securing first place on the modular framework to provide permanent, component-based buildings and facilities for the ESFA’s new secondary schools block replacement programme. They won this procurement competition with others from the off-site construction sector, securing top spot against 64 other bidders. Being awarded first place immediately secured two projects with a combined value of £12 million, with the potential to realise further schemes within the £250 million funding allocated to the lot.

A track record of delivering these projects on time and within budgets means the management team can replicate their approach on each successive new contract – a great confidence builder with clients and main contractors. A case in point is the £25m contract awarded to Caledonian by Bowmer & Kirkland, announced in the last few weeks, for the 680 bedroom First Way Campus student development in Wembley.

The ability of Caledonian’s modular building system to help meet the strict deadline dates on this project, which required handover in time for Euro 2020, helped secure this contract. As did their pre-engineered fire compliant modular solution suitable for a high rise development, which rises from 7 to 11 floors.

Other recent contracts wins include the MOD Single Living Accommodation (SLA) for MoD Lyneham in Wiltshire as part of a £35m Kier development. Part of the Army Basing Programme, the project will create 296 rooms over 5 blocks, providing accommodation for troops returning from overseas and relocating within the UK. The latest contract continues a long partnership with the MOD, with the team successfully completing 1,145 rooms over 12 blocks on the same base for Kier in 2012/13.

Caledonian Modular prides themselves on the fact that their projects look as authentic as a traditional-build, indeed they are indistinguishable, while remaining as efficient and cost-effective as they do. By sticking to what they know – modular and off-site construction systems – underpinned by BIM, DFMA and lean manufacturing, this Nottingham based company is raising industry standards and demonstrating how modular buildings have the ability to resolve the UK’s building shortages quickly and efficiently.

To find out more about Caledonian’s modular building system, visit www.caledonianmodular.com. Alternatively, call 01636 821645.
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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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