UCL's civil engineering students don't rely on textbooks alone to teach them about monocoques – they have a demonstration project floating above the main laboratory.
The civil engineering students of University College London have been presented with a new tool to teach them about structures. In the department's Gower Street building, floating through the upper half of the double-height laboratory hall, are two rows of plywood cabins. Professor James Croll, head of the department, proudly explains that they function like box-girder bridges, with their walls and floors forming rigid semi-monocoque structures.

The whole construction, down to the rows of screwheads fixing the wall panels and the stainless steel pin joints in the two supporting columns, has been exposed to view as a teaching aid.

First and foremost, however, the cabins function as eight permanent offices for department staff. They are a highly original solution to the problem of installing a mezzanine floor within the building shell.

As well as being an engineering demonstration project, the new offices radiate a strong architectural style. The plywood skins of their cabins appear flawlessly taut and smooth with their natural birch finish. The stainless steel screwheads in the plywood panels are neatly arranged in double rows that echo in miniature the industrial rivets of the old building's exposed steel columns and beams. The gangway passing between the two rows of cabins, and the steps leading up to it, are bordered by slimline balustrading in charcoal-grey-painted steel, with smooth grey terrazzo flooring to match.

Croll talks admiringly of the synergy between the project's consultant architect, Ian Simpson Architects, and structural engineer, Martin Stockley Associates, both Manchester-based practices that he selected by competitive interview. "The major concepts of their design were generated by the structural engineers," he says. "That conformed to what we were looking for." Beneath the cabins spreads the original laboratory space, with its headroom cut in half. However, one-quarter of the original hall, where an existing heavy buckling machine stands, remains free of the intruding cabins and has been retained with its original headroom.

"The existing hall is quite busy, with columns, crane rails and engineering equipment," says Ian Simpson. "So we wanted to insert something clear and pure that would maintain the integrity of the double-height space, otherwise there would be no clarity at all. And we wanted to add an element of theatricality." The free-floating cabins suit Simpson's architectural agenda of dramatically differentiating the new interventions from the existing building fabric. This agenda was underlined by the fact that the existing building is one of the few university buildings to be grade I-listed. Although built as recently as 1894, it makes up one wing of a neoclassical ensemble of Portland stone buildings arranged symmetrically around a courtyard and colonnaded portico, designed in 1827 by William Wilkins, architect of the National Gallery.

Although the original interior of the building is industrial, with exposed steel columns and beams and white glazed bricks, English Heritage insisted that the new structures should stand proud of the external walls. So the outer partitions of the offices have been set back 1.5 m from the original stone front wall facing Gower Street.

The downside of this double arrangement of outer walls is that the offices must now rely on mechanical ventilation, even though the outer windows are conventional sashes. Staff have complained about the fierceness of the air supply, and in a few cases have blocked off the air grilles, which are inconveniently located next to their desks.

The £2.4m refurbishment of UCL's civil and environmental engineering department extends well beyond the new pods in the ground-floor laboratory hall. Contained entirely within the historic shell of the building, the project has provided 1000 m2 of additional floor space, and some 2400 m2 of the 4000 m2 existing floor space has been refurbished and reordered in an attempt to solve several accommodation problems at once.

The interiors of the 100-year-old building had been crying out for refurbishment. In addition, more space had to be found to house Croll's growing department, which has more than 290 staff and students. Not least, he wanted to rationalise the internal layout, which had "labs and teaching spaces all over the place".

Part of Croll's plan was to bring together the laboratories of the department's five sections, so that they could all be serviced directly by a central workshop. Two existing workshops existed in basements below the central courtyard, and Simpson and Stockley created more laboratory space and a tiered 100-seat lecture theatre by excavating the undercroft below the ground floor. A feasibility study by the college's estate department had suggested that an extra attic storey could be added behind the parapets, but trial digs showed that a basement could be excavated with very little underpinning to the original 4 m deep footings. This basement solution appealed to Croll, as it would keep the attic option in reserve for a later phase, whereas the reverse sequence would not be possible.

Croll's interest in architecture runs deeper than the stylishness of his department's new accommodation and is even informing a reformed curriculum. In particular, he admires the architectural education system, in which design projects play a central role.

"We are committed to changing the way we teach engineering," he says. "Our students are overburdened by an education that doesn't stimulate the mind. We look over our shoulders and see that architects are taught in a way that is exciting and enlivening." Accordingly, Croll is keen to borrow project-based teaching methods in studios from schools of architecture. "When I was an engineering student in the old days, we were taught in vast drawing studios. These went out of favour when engineering became more theoretical. Now we're trying to recreate these open studios again, as they provide teaching environments that are both educational and social. We have also created a common room for graduates, who are usually isolated working on their own." The refurbishment project was handed over last November, two months late. Croll admits that the disruption of moving in during term time has left "most of the staff still reeling". He has also been dismayed by the proliferation of exposed pipework, cabling and ducting, which has spread like jungle lianas through many of the new and refurbished spaces.

On the other hand, Croll is enthusiastic about "the light, bright modern spaces, which bring huge benefits for staff and students". He also claims that the new common room and studios "have created a better social mix and a bit of a buzz", while the reordering "has united the department for the first time".

Most of all, UCL's civil engineering department has acquired a smart new addition that reads clearly both as an engineering and an architectural structure. As a bonus, the synergy between the two disciplines has fed back into the department's curriculum.

How the pods float in space

The new mezzanine floor of eight offices, inserted within University College London’s department of civil and environmental engineering building, has been designed as a series of box girders or rigid semi-monocoque pods, in which the external skin strengthens and stiffens the internal frame. The elongated pods seem to float in space, spanning 13 m between an existing cross wall and two new spindly steel columns, and cantilevering out a further 4.5 m into thin air. Understandably, they are highly engineered structures, yet the construction of the floors and walls is fairly low-tech, mainly consisting of softwood studwork sheathed in plywood. The monocoque structures draw their strength and stability from the rigid fixing of the plywood sheathing to the studwork by means of gluing and screwing. “We costed out the frames in steel and timber, and we found that timber was more cost-effective and significantly lighter,” explains Julian Broster, associate of structural engineer Martin Stockley Associates. The detailed design involved more elaborate engineering. The studs are typically double sections of 75 × 100 mm, and the sheathing is double 18 mm panels of birch-finished structural plywood. The timber studs were bolted together and strengthened along their edges by steel flitch plates. More steel reinforcement was needed around window and door openings, and in the floor around the two columns. As there are no lids to the monocoques, lateral restraint is provided by timber “pelmets” that span between the original steel ceiling beams and are fixed by steel brackets. Although these brackets do not carry the pods, they have been designed to catch them if fire burns away their permanent fixings.