Offsite construction is helping to meet the quality and cost requirements of a variety of modern buildings. Innovation within offsite construction means it is now possible to offer greater flexibility in the design of modular buildings than ever before. The offsite sector has been able to do this by introducing modern hybrid systems that offer all the advantages of conventionally built structures, but with the speed and quality of offsite construction systems. The beauty of these buildings is that they are permanent and are guaranteed to last as long as you would expect a traditionally-built structure.
One of the most significant advances in the design of such buildings has been the introduction of corner-loaded modules, which greatly increase the scope for design. These systems can also generate significant cost savings on site and throughout the lifetime of a building.
Corner loaded modules allow for the construction of more visually engaging buildings with, for example, full height glass walls. Glazed walls are now possible because of the advances we have made in panel bracing, which means that the systems can be engineered into different structural members contained within the module.
Technical developments such as these mean that offsite buildings now offer much greater design flexibility. For example, by choosing an offsite corner-loaded system, units can be supplied either fully serviced – and with watertight exterior cladding – and ready to be craned into position, or as flat pack panels where there is a site access issue, which are easily assembled and finished on site.
Hybrid offsite systems are based around a steel frame, which provides greater architectural freedom in an economical and space-efficient building. The steel frame system allows the building designer to literally break out of the box and specify modules that are non-rectangular in design 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 to be incorporated into the design – a feature that is becoming very popular in domestic and commercial buildings, as building designers look to maximise the benefits of natural daylight, for health and well being benefits.
There are other advantages of corner loaded offsite systems, such as the savings 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 to significant benefits in terms of sustainability.
Many customers are looking for a seamless link with an existing traditionally-built structures. This means having to create a visual match externally, along with ensuring that internal floor heights are the same. In response to this, we adapted our corner loaded system so that floor levels could be set at any height required to suit existing floor levels, avoiding any unnecessary steps or slopes.
Exterior finishes are an important part of any offsite building and help to establish the character and context within local surroundings. The options for modular buildings are the same as those for any other type of building system, ranging from brick and cedar cladding to lightweight aggregate panels that provide 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 enhancing its performance.
A key consideration is whether to match the aesthetics of adjacent buildings. Externally, conjoined buildings can be matched by re-rendering – making the new extension indistinguishable from the traditionally-built main structure. Our modular systems also provide the opportunity to replicate the predominant architectural features in the immediate surroundings, or to go for contrast, for example, aluminium cladding or glass feature walls.
And it is not just the exterior of the building where innovation in offsite systems has been made. Effective interior planning is essential to establish a functional and pleasant environment in which to teach, learn or work. Modern hybrid offsite techniques allow for features such as vaulted ceilings and roof-lights, which are now often incorporated to deliver the feeling of space and to gain all the benefits of natural daylight. In a similar way, movable partitions in selected areas can provide the flexibility to change the interior space to meet different room sizes and to suit a variety of uses.
A recent project to use this type of construction is Lewisham Hospital, in association with Kier London. The design for a new Outpatients’ Suite at the hospital incorporated the Unitrex system to create a double storey permanent building, as part of an overall £12m investment to extend and refurbish the hospital.
A Government survey found that hospital buildings had some of the highest average Carbon Dioxide emissions and, as a result of this, the health sector is looking for ways to improve its energy efficiency and reduce its carbon footprint.
As it serves a large population in the London Borough of Lewisham and surrounding areas, this busy hospital has restricted site access, which meant that all deliveries had to carefully planned and agreed in advance with the client.
Due to the hospital providing Emergency Department services, this meant it was vital to have clear access at all times to these essential areas and therefore extra care had to be taken to ensure normal operations were not affected.
For the Outpatients’ Suite, which links onto the main hospital building, it was also important that it was completed within a very short timeframe, as the work was scheduled in phases. This meant that as soon as the Outpatient Suite was handed over, it could be occupied by other services, 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 modular building’s capabilities due to the bespoke nature of its service. The design of the Outpatient Suite incorporated timber and steel, with wall panels throughout. There is also a three storey circulation tower, which links the new and existing buildings. The tower is built with a concrete roof and floors and is designed so that hospital staff and patients can easily move between the existing and new building at all three levels, providing greater convenience. One of the requirements of the building was to ensure that there was no reverberation between the floors adjacent to the corridors, which meant reinforced floors were provided to reduce any sound or vibration.
The building has been designed to achieve BREEAM Very Good and therefore meets all the requirements for air tightness, improving energy efficiency and reducing the carbon footprint. The architect provided an A-rated specification for all building components, as part of achieving the project’s environmental requirements. A very visible display of the building’s green credentials is that it incorporated a sustainable sedum roof, which will provide a haven for grass and plants 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 doing this as the three storey building will be overlooked by a nearby seven storey hospital ward, improving the outlook for patients.
It was important on this project to ensure that the new building complemented the style of the existing hospital. This meant that cladding was selected to match the finish of the existing structure, which makes it virtually indistinguishable from the main building. Therefore Microrib cladding was specified in metallic silver, which matched the modern external façade of the existing hospital building that it joined. To enhance its aesthetics, the ceiling of the Outpatient Suite featured a light well – again a distinctive architectural feature.
The design of the internals was carefully planned too, down to the detail of the integrated plumbing system, which was included with a frame assembly to avoid the need for site studding. This was part of the hospital’s requirement, as it speeds up installation on site in order to meet the rigid build schedule.
Modern offsite systems, like the one used at Lewisham Hospital, also offer the potential to achieve the very highest ‘A’ rated energy performance, by optimising 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 about because of a lack of a joined up approach between, say, the roofing and façade contractor, which can result in a poor air tight seal between these two critical building elements and therefore lower thermal performance. Offsite construction systems overcome this problem because the elements are pre-fabricated in quality assured production facilities, which ensures an excellent air tight seal site.
Summary Research has shown that the return on investment of an offsite constructed building has proven to be significantly greater than that of a traditional build. This is clearly demonstrating how offsite construction meets the needs of the health sector in many ways and not least due to the excellent lifetime values of buildings. Lewisham Hospital’s outpatient’s suite is a very good example of offsite construction working really well to meet both the building performance requirements 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 within the constraints of short timeframes and the restrictions associated with access to site. However, due to major innovations in design and the development of hybrid systems, this means that non-standard units can be produced and sustainable technologies can be integrated into the design. This also helps to enhance a building’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 and offsite construction can help the buildings of the future to meet all requirements for performance, design, scheduling and cost.