An Off Site Building is for Life

Here, Managing Director of Terrapin, looks at how the off site industry has responded to the need to provide well-designed, aesthetically pleasing permanent buildings that meet the latest building performance requirements.

“Over the years, off site buildings have changed from being merely providing temporary classrooms to representing a long term solution to the building requirements of the education sector.

Education providers have recognised how off site construction can offer a bespoke product that is highly engineered to meet the more stringent legislative requirements. Many off site buildings, for example, achieve BREEAM ‘very good’ or ‘excellent’ and it is this focus on energy efficiency, design and performance that is challenging past perceptions about cold, draughty temporary classrooms.

A constant issue within the education sector is the need to construct new classrooms, often during a very short lead time – for example, during the school holidays, or whilst keeping the rest of the school building operational, which again imposes severe restrictions on the contractors.

The off site sector has responded to these requirements through the introduction of modern hybrid systems that offer all the advantages of conventionally built structures, but with the speed and quality of off site 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 - a lifetime of approximately 60 years.

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

These systems allow for the construction of more visually engaging buildings with, for example, full height glass walls. Glazed walls are now possible in off site systems, 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 off site buildings now offer much greater design flexibility. For example, by choosing an off site 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, which are easily assembled and finished on site.

Hybrid off site systems

Within our range, these hybrid corner loaded 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 off site buildings are indistinguishable from traditionally built structures. These hybrid systems also allow corner-to-corner glazed walls to be incorporated into the design - a feature that is becoming very popular in a number of public buildings, as they look to maximise the benefits of natural daylight.

“Modern hybrid off site systems are indistinguishable from traditionally-built structures”

There are other advantages of corner loaded off site 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.

We find that many clients are looking for a seamless link with an existing traditionally-built structure. 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 off site 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.

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 off site 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 off site 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.

Case study: Hastings High School

Hastings High School in Leicestershire is a great example of how off site construction can be put to best use to deliver a permanent structure that meets aesthetic and performance requirements, but within the constraints of time and space.

The project involved our Unitrex panelised system, which uses standardised system components and quality-assured factory fabrication to create an aesthetically pleasing double storey classroom building. The narrow road at Hastings High School meant that traditional volumetric offsite systems could not be transported to site without specialist lifting equipment, which would have added significantly to the cost of the project. The innovative system meant it was possible to create a weathertight seal within five days, which was achieved by carrying out the majority of the fabrication of the ground floor steelwork and panels in factory controlled conditions.

One of the reasons for choosing this system was that it enabled the creation of large clear-span rooms, as it eliminates the need for internal supporting walls, as two or more modules can be supported on goalpost beams. Due to the versatility of the Unitrex system, it meant we could link the new classroom to the existing school building at the finished floor level. This was required in order to avoid any unnecessary steps or slopes, ensuring a seamless link between the existing and new classrooms.

Building Schools – an opportunity

The Government’s policy change around Building Schools for the Future (BSF) does present opportunities for the off site sector. This is because new school buildings will still be needed, either as an extension to existing or as a direct replacement to a building.

With off site construction representing excellent value for money, the education sector is therefore focusing closely on the opportunities it offers.

As education building budgets face an inevitable squeeze, we have already responded to the new age of austerity by offering an opportunity to lease off site buildings. This option means that schools have much more predictability when it comes to long term budgeting, avoiding the unforeseen costs of conventional build being delayed, for example, due to the weather.

Some local authorities are also taking advantage of the option of 10 year rental, rather than outright purchase, as this makes for a more flexible payment arrangement, especially since hired buildings come with the same performance guarantees as new stock. When it comes to overall value for money, research has shown that the return on investment of an off site constructed school building has proven to be significantly greater than that of a traditional build.

Many forward-thinking local authorities have, for a long time, embraced off site construction, particularly in the case of schools, where tight build schedules and restricted access often make it the only practical option. Good project management is all important and this is where our expertise comes into play, by managing the process from concept, through to design and build. In addition, we can assist in meeting the requirements of planning applications, guiding our clients through the process to ensure the building is delivered on time and to budget.

The introduction of modern hybrid off site systems, which have all the design freedom and performance provided by traditional buildings, means that we can expect to see many more educational buildings constructed in this way. With the focus within the education sector on achieving even better value for money, then it is today’s flexible approach offered by off site construction that will help to shape the educational landscape of the future.”