School building: Top form

Schools construction is often caricatured as a simplistic battle between design quality and economic efficiency. The old Building Schools for the Future may have appeared to actively champion design but it was also dismissed by many as profligate and self-indulgent.

The alternative Priority Schools Building Programme, championed by the government, may well embrace standardisation and efficiency but this too is dismissed by many as churning out production-line monotony that is low on design quality and architectural charisma. Is there a third way? Can a school be both efficient and cost-effective while achieving the innovation and variety that is essential for good design? Well, a new schools construction model jointly developed by architect Sheppard Robson and contractor Willmott Dixon aims to be just that. And central to this strategy is its soaring glulam roof.

According to the design team publicity, the Liverpool schools model “creates a flexible and economic architectural ‘shell’ in which individual interior components are added to create a mix of learning and social spaces bespoke to the individual school’s requirements”.

Essentially, the concept, as its informal name “schools within a shed” suggests, is based on a structurally independent outer superstructure concealing a secondary inner structure which can be modified to suit specific school requirements.

The outer structure is spanned by a glulam bowstring truss roof, thus far capable of spanning up to 56m column free. The inner structure comprises a steel frame with concrete floors and is configured to form the various internal spaces required by the school. It is based on an 8m grid which allows classrooms of up to 64m².

So far, three schools have been built to this model. First came £15.3m Notre Dame Catholic College, a 950-pupil school and sixth form in Liverpool. In a dynamic reflection of the speeds and efficiencies the model claims to be able to realise, the build period was just 56 weeks and the cost per square metre was just £1,459, almost half the cost of comparable BSF budgets and much more similar to PSBP costs - an important consideration as Liverpool council had to fund the regeneration of its education estate after the cancellation of BSF.

Since Notre Dame’s completion in 2013 two further Liverpool schools have followed, Archbishop Beck and Archbishop Blanch, and there are plans to roll out the concept to other schools in the near future.

While the application of the concept onto three distinct schools shows it can be modified to fit various circumstances and needs, the key fixed parameter of the model is the roof. By forming a completely separate structure to the accommodation below, the roof allows any number of school layouts and configurations to be created.

While all three schools follow a typical format of classrooms arranged around the perimeter of the envelope and a large top-lit void to the centre, there are subtle variations in how this layout is achieved.

Notre Dame embeds the idea of community by configuring the void as a large, central communal space, Archbishop Beck adopts a more collegiate, clustered arrangement to classrooms and teaching areas, while Archbishop Blanch disperses its classrooms around two central courtyards.

Under one roof

The key point is that this level of variation is permitted by the structural independence of the over-sailing roof which essentially acts like a lid to a giant hangar. The roof itself is formed by a primary structure of glulam beams supporting steel purlins and aluminium panels built up in a similar fashion to a Kalzip roof. It is in turn supported by an insulated metal frame envelope which forms the hangar’s outer skin.

Spans between the glulam roof beams can either be solid or glazed, the latter permitting light into the centre of potentially deep-plan buildings. The system can also incorporate the addition of photovoltaic panels onto the solid stretches of roof. Impressively the roof incorporates no joints across its span and is fitted with two gutters on either side.

The glulam beams, which vary from 48m to 56m on all three schools, are prefabricated and brought onto site for assembly in three separate parts. The inherent speed the prefabrication process allows is central to the programme efficiencies the Liverpool schools model claims to deliver, but how can the higher cost of glulam be presented as a cost saving?

Sheppard Robson associate partner James Jones explains how: “Yes, steel would have been cheaper and glulam comes with a cost premium. But the glulam was incredibly important to the whole schools concept and actually came as a requirement from Liverpool council and pre-dated our involvement.

“The advantage is that it justifies the use of timber on other areas of the building which also presents a cost-saving on finishes. This in turn embeds a quality of finish and robustness to internal walls and spaces that cannot be value engineered out. Additionally, the entire model isn’t determined by classroom sizes or a restrictive area schedule which can also lead to an unnecessarily complicated and less cost-effective design. The combination of these measures means that there is flexibility to ensure that going over in one area still meant that other areas of the design could become even more efficient to keep costs down.”

Standard issue schools

For Mike Lane, director at Willmott Dixon, several other roof features proved useful in keeping costs down. “There was definitely a cost differential in having such large spans - a smaller building would have worked out more expensive. Additionally, the lack of intermediate columns also represented a saving as did the early integration of the main contractor and structural frame subcontractor into the design team.”

Lane also presents key observations on how the impressive programme was achieved. “The fact we were essentially building a big shed helped. On a conventional build, a key driver would be getting the envelope watertight before internal trades could move onto site. But here we could start everything, including internal trades, at one end and build to the other because the interior was protected by the secondary ‘shed’ envelope.”

Lane also cites the lack of internal ceilings and strong local supply chain collaboration and engagement as factors that saved both time and money. “Services in ceiling voids are left exposed with no suspended ceilings. Not having to perform repetitive visits into ceiling voids for service installation saved six weeks off the project. As did working with local mechanical engineers using localised systems and equipment.”

For Jones, a key long-term cost saving of the system is the fact that the independent roof enables the school to be future-proofed for multiple alternative uses. “In theory, everything inside the school could be stripped out and you’d still have a void underneath the roof which could be used for all manner of activities, such as commercial or leisure.”

He compares the arrangement of a naturally lit and ventilated perimeter supported by a service zone and wrapped around a central void to that of a traditional commercial office building.

But for Jones, the key advantages of the Liverpool schools model is that it is has a “simple form, is cost-effective, quick to build and simple to maintain”. Does this then make it a standardised school? Particularly when considering that the anchor concept within the model is the fixed component of a modular glulam roof?

For Jones the answer is two-fold. “Yes, the model is based on a consistent component system. But it is one that can be applied and translated to a variety of conditions thereby avoiding the monotony and repetition that can sometimes give standardisation a bad name.”

Clearly, the utilitarian shed aesthetic of the roofs in the Liverpool schools model will not be to everybody’s liking. Moreover, it will do little to quell the concerns of those who believe that standardised identikit solutions for school design, even if they are restricted to the roof, stifle design flair and creativity.

But there is no denying the fact that the roof solution does achieve a combination of cost and programme efficiency whilst permitting the kind of layout flexibility that, rightly or wrongly, is not commonly associated with standardised schools systems. The glulam is also central to this achievement, providing a modular structural efficiency that is crucial for programme targets but also softening the industrial aesthetic that steel would doubtless have engendered.