The blaze that destroyed the university’s new laboratory offered a stark reminder of the risks construction can face. But what impact will this incident have on the future of timber-framed builds?
When fire ripped through a new laboratory at the University of Nottingham last week, it brought back an uncomfortable debate for firms about the risks associated with timber-frame buildings under construction.
Fears about the construction method’s vulnerability to fire have been voiced for many years but the industry has taken steps to mitigate some of those worries.
As main contractor on the £20m Carbon Neutral Laboratory for Sustainable Chemistry, Morgan Sindall had carried out tests on regulating fire spread in the structure, which was built from engineered timber beams and cross-laminated timber panels.
Fire investigation experts and insurance loss adjusters are investigating the blaze site.
Nottinghamshire Fire and Rescue Service is working with the university and its contractors to investigate the cause and recover as much of the site as is possible.
The blaze tore through the new laboratory after the initial alarm was raised at 8:36pm on Friday 12 September and the speed that it engulfed the site has again underlined the susceptibility of timber buildings to fire during the construction process.
But insurers this week made clear their commitment to assisting contractors involved in building timber-framed structures.
Industry body the Association of British Insurers reassured contractors they will continue to provide cover to construction projects regardless of structural framing material, with each case assessed on an individual basis.
An ABI spokesman said: “A major event like the incident at the University of Nottingham will not put people off using these systems and nor will it dissuade insurers from offering cover.
“The risk will continue to be assessed on an individual basis and the sector will continue to be well looked after”
Association of British Insurers
“There will be no blanket refusal to cover projects using timber-framing systems, the risk will continue to be assessed on an individual basis and the sector will continue to be well looked after.”
Construction work on the £20m development had begun under a £15.8m deal with Morgan Sindall in September 2013 and it was due to be handed over to the client in April next year.
Although it was not due to have a sprinkler system fitted even after completion, it would have had a 30-minute fire resistance to allow time for evacuation.
Construction News visited the site just hours before the entire building was gutted.
Morgan Sindall project manager Nick Hilton had said: “We spent lots of time working with the chemistry department on tests including fire spread and chemical attack. The completed building will feature fire suppression throughout but there will be no sprinkler system.”
The laboratory is not the first timber structure to be destroyed by fire during construction.
Steps taken in recent years
Concerns from fire officers over the methods used following severe fires in 2006 and 2007 prompted representatives from the timber industry to develop guidance for designers and contractors on the management of timber-framed sites to help mitigate fire risk.
“Statistics from the DCLG demonstrate that only a small percentage of building fires involve structural timber”
Structural Timber Association
The industry responded by working with fire officers and engineers to develop the 16 Steps to Fire Safety booklet, which provides advice on how to reduce fire risk.
It includes advice on securing sites against arson attack, on inspection regimes and fire detection and warning.
A recent study of fire in timber framed structures by the Department for Communities and Local Government suggested there was little difference in terms of fire damage between completed timber-framed buildings and those of other structural frame.
But it added that during construction there was “evidence that the difference between the distributions of the amount of damage in non-residential buildings is statistically significant between non-residential buildings of i) timber frame and ii) no special construction”.
A carbon-neutral blueprint
The laboratory was set to become a blueprint for eco-friendly designs at locations around the world for pharmaceutical giant and project sponsor GlaxoSmithKline.
With offices and teaching labs on the ground floor, labs and write-up areas on the first floor and a top-floor plant room, the main structure had been built using glulam timber beams and columns, while cross-laminated timber (CLT) panels were used in the wall, floors and roof.
Particular consideration was paid to the fire retardant on the timber members, with stringent tests to protect against the spread of fire and to ensure the fire resistance at the fixing points between each member.
Steps included a wooden plug-bolt fitted into the countersink behind the bolt fixing.
The bulk of the CLT panels were 200 mm thick, with panels bolted together to form the continuous ground floor to plant floor shafts.
B&K Structures was brought in for that work as well as the installation of the 300 x 400 mm and 450 x 450 mm glulam columns at 6-8 m centres. The largest of the glulam beams spanned 8 m, were 1.5 m deep and weighed just 1.8 tonnes.
Floor plates at first-floor lab level measured 3,500 sq m. A reinforced concrete slab with a cast-in underfloor heating system had been placed on the ground floor.
The scheme is sited on reclaimed brownfield land and has been treated using an array of vibro stone columns - a departure from the initial plan to use CFA piles and save more embodied carbon.
Reinforced concrete use was limited to the two retaining walls at the base of each of the building’s wings, the ground-floor slab and the pad foundations it sits upon.
A spokesman for trade body the Structural Timber Association said: “Any large-scale fire is a concern, and while we do not know the specifics as yet, our thoughts are with anyone affected by the recent incident.
“Statistics from the DCLG demonstrate that only a small percentage of building fires involve structural timber.
“Nevertheless, the STA continues to ensure fire safety is paramount, with our sector leading the way in terms of safety and sustainability.”
He said the STA was working hard to underpin the safety of buildings during construction and is “proactively working and engaging with a range of stakeholders to further improve the performance of structural timber-based buildings”.
“We must also recognise the hard work that went into preventing this incident from being much worse”
Wayne Bowcock, NFRS
It is carrying out technical research, guidance preparation and training course delivery.
The building may be gone, and more than a year’s construction with it, but the determination to see the project through to completion remains.
The university’s vice-chancellor Sir David Greenaway said “it may now take a bit longer, but it will still be delivered” and a university spokesman confirmed it was determined to rebuild the project.
As NFRS deputy chief fire officer Wayne Bowcock said: “It’s terrible that the University of Nottingham and the wider education community have lost what was set to be an iconic building, but we must also recognise the hard work that went into preventing this incident from being much worse.”