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Modern Offsite Buildings

Adrian Day, Managing Director of Terrapin, discusses how offsite construction ishelping to meet the quality and cost requirements of a variety of modernbuildings.

 “Innovation within offsite construction means it is now possible to offer greaterflexibility in the design of modular buildings than ever before. The offsite sectorhas been able to do this by introducing modern hybrid systems that offer all theadvantages of conventionally built structures, but with the speed and quality of offsite construction systems. The beauty of these buildings is that they arepermanent and are guaranteed to last as long as you would expect atraditionally-built structure.

One of the most significant advances in the design of such buildings has beenthe introduction of  corner-loaded modules, which greatly increase the scope for

design. These systems can also generate significant cost savings on site andthroughout the lifetime of a building.

Corner loaded modules allow for the construction of more visually engagingbuildings with, for example, full height glass walls. Glazed walls are now possiblebecause of the advances we have made in panel bracing, which means that thesystems can be engineered into different structural members contained withinthe module.

Technical developments such as these mean that offsite buildings now offermuch greater design flexibility. For example, by choosing an offsite corner-

loaded system, units can be supplied either fully serviced – and with watertightexterior cladding – and ready to be craned into position, or as flat pack panelswhere there is a site access issue, which are easily assembled and finished onsite.

Hybrid offsite systems

Within our range,these hybrid corner-loadedmodules are based around asteel frame, which provides

greater architecturalfreedom in an economicaland space-efficient building. The steel frame system allows the building designerto literally break out of the box and specify modules that are non-rectangular indesign or have internal atria or balconies.

For clients, this means offsite buildings are indistinguishable from traditionally-built structures. These hybrid systems also allow for full height glazed walls tobe incorporated into the design - a feature that is becoming very popularin domestic and commercial buildings, as building designers look to maximisethe benefits of natural daylight, for health and well being benefits.

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There are other advantages of corner loaded offsite systems, such as thesavings that can be made on foundation materials and therefore cost. The use of fewer foundation materials, which tend to have high embodied energy content,also results in a building with a smaller carbon footprint and that leads tosignificant benefits in terms of  sustainability. 

We find that many customers are looking for a seamless link with an existingtraditionally-built structures. This means having to create a visual matchexternally, along with ensuring that internal floor heights are the same. Inresponse to this, we adapted our corner loaded system so that floor levels couldbe set at any height required to suit existing floor levels, avoiding anyunnecessary steps or slopes.

Exterior finishes are an important part of any offsite building and help toestablish the character and context within local surroundings. The options formodular buildings are the same as those for any other type of building system,

ranging from brick and cedar cladding to lightweight aggregate panels thatprovide variety and interest in colour and texture.

On some projects, customers are recognising that the exterior render of the modular building could be refurbished relatively easily and cost-effectively,providing a completely different, updated look to the building, whilst enhancingits performance.

A key consideration is whether to match the aesthetics of adjacent buildings.Externally, conjoined buildings can be matched by re-rendering – making thenew extension indistinguishable from the traditionally-built main structure. Our

modular systems also provide the opportunity to replicate the predominantarchitectural features in the immediate surroundings, or to go for contrast, forexample, aluminium cladding or glass feature walls.

And it is not just the exterior of the building where innovation in offsite systemshas been made. Effective interior planning is essential to establish a functionaland pleasant environment in which to teach, learn or work. Modern hybrid offsitetechniques allow for features such as vaulted ceilings and roof-lights, which arenow often incorporated to deliver the feeling of space and to gain all the benefitsof natural daylight. In a similar way, movable partitions in selected areas canprovide the flexibility to change the interior space to meet different room sizesand to suit a variety of uses.

The most recent project to use this type of construction is Lewisham Hospital,for which we worked in association with Kier London. The design for a newOutpatients’ Suite at the hospital incorporated our Unitrex system to create adouble storey permanent building, as part of an overall £12m investment toextend and refurbish the hospital.

A Government survey found that hospital buildings had some of the highestaverage Carbon Dioxide emissions and, as a result of this, the health sector islooking for ways to improve its energy efficiency and reduce its carbon footprint.

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Challenges

As it serves a largepopulation in the LondonBorough of Lewisham and

surrounding areas, thisbusy hospital has restrictedsite access, which meantthat all deliveries had tocarefully planned andagreed in advance with theclient.

Due to the hospitalproviding EmergencyDepartment services, this

meant it was vital to haveclear access at all times tothese essential areas andtherefore we had to takeextra care to ensure normaloperations were notaffected.

For the Outpatients’ Suite,which links onto the mainhospital building, it was

also important that it wascompleted within a veryshort timeframe, as thework was scheduled inphases. This meant that assoon as the Outpatient Suite was handed over, it could be occupied by otherservices, including children’s and adult outpatient services.

Design and build

Lewisham Healthcare NHS Trust was looking for a non-standard width for the

new Outpatients’ Suite, which was perfectly within Terrapin’s capabilities due tothe bespoke nature of its service. The design of the Outpatient Suiteincorporated timber and steel, with wall panels throughout. There is also a threestorey circulation tower, which links the new and existing buildings. The tower isbuilt with a concrete roof and floors and is designed so that hospital staff andpatients can easily move between the existing and new building at all threelevels, providing greater convenience. One of the requirements of the buildingwas to ensure that there was no reverberation between the floors adjacent tothe corridors, which meant Terrapin provided reinforced floors to reduce anysound or vibration.

The building has been designed to achieve BREEAM Very Good and thereforemeets all the requirements for air tightness, improving energy efficiency and

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reducing the carbon footprint. The architect provided an A-rated specification forall building components, as part of achieving the project’s environmentalrequirements. A very visible display of the building’s green credentials is that itincorporated a sustainable sedum roof, which will provide a haven for grass andplants to flourish, as part of reducing the building’s carbon footprint. As well as

being of great environmental benefit, there were also aesthetic reasons for doingthis as the three storey building will be overlooked by a nearby seven storeyhospital ward, improving the outlook for patients.

It was important on this project to ensure that the new building complementedthe style of the existing hospital. This meant that cladding was selected to matchthe finish of the existing structure, which makes it virtually indistinguishablefrom the main building. Therefore Microrib cladding was specified in metallicsilver, which matched the modern external façade of the existing hospitalbuilding that it joined. To enhance its aesthetics, the ceiling of the OutpatientSuite featured a light well – again a distinctive architectural feature.

The design of the internals was carefully planned too, down to the detail of theintegrated plumbing system, which was included with a frame assembly to avoidthe need for site studding. This was part of the hospital’s requirement, as itspeeds up installation on site in order to meet the rigid build schedule.

Modern offsite systems, like the one used at Lewisham Hospital, also offer thepotential to achieve the very highest ‘A’ rated energy performance, byoptimising insulation and energy performance. With traditional building methods,it is more difficult to meet such high performance, without, for example,incorporating extra wide cavities to accommodate more insulation and then

there is the issue of achieving adequate airtight seals. This can come aboutbecause of a lack of a joined up approach between, say, the roofing and façadecontractor, which can result in a poor air tight seal between these two criticalbuilding elements and therefore lower thermal performance. Offsite constructionsystems overcome this problem because the elements are pre-fabricated inquality assured production facilities, which ensures an excellent air tight sealsite.

Summary

Research has shown thatthe return on investment of an offsite constructedbuilding has proven to besignificantly greater thanthat of a traditional build.This clearly demonstrateshow offsite constructionmeets the needs of thehealth sector in many waysand not least due to theexcellent lifetime values of 

buildings.

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Lewisham Hospital’s outpatient’s suite is a very good example of offsiteconstruction working really well to meet both the building performancerequirements and site access restrictions.

Offsite construction is becoming a popular choice in the health sector, due to the

fact that it can deliver permanent, high performance buildings, working withinthe constraints of short timeframes and the restrictions associated with access tosite. However, due to major innovations in design and the development of hybridsystems, this means that non-standard units can be produced and sustainabletechnologies can be integrated into the design. This also helps to enhance abuilding’s BREEAM rating. 

With the current requirements for good value, high performance buildings,offsite construction is rising to the challenge to meet modern building needs.Innovation within offsite construction means design is no longer restricted andoffsite construction can help the buildings of the future to meet all requirements

for performance, design, scheduling and cost."

 As a leading UK provider of offsite construction solutions, Terrapin has been in

the business of permanent and temporary solutions for 60 years. Off site

construction delivers fast, accurate and affordable solutions to permanent,

temporary and relocatable building requirements for healthcare, education,

developer and commercial projects.

Compared to conventional building methods, Terrapin’s modular solutions reduce

time on site, cut the number of deliveries and are virtually unaffected by 

weather considerations. Importantly, for a site where disruptions must be kept 

to a minimum, the offsite construction approach creates much less noise and 

interference to the day to day operation of the site and its occupants.