Potential perils of modern methods of construction
- Modern methods can provide cheaper, quicker and greener ways to build properties, but some materials and methods can increase fire and flood risks
- Joined-up thinking is needed throughout design, build and maintenance process to ensure true risks are recognised
- Zurich keeps its finger on the pulse of the construction industry and has experts who can help assess MMC risks
Construction practices and technology are developing rapidly, leading to the erection of taller and more complex buildings – often using modern methods of construction (MMC).
While every form of construction comes with an element of risk, some MMC introduce large quantities of combustible materials into their designs such as wood, polystyrene and recycled materials like tyres and pallets. Using such materials can alter both the probability of fire and the potential scale of loss should a fire occur.
And it is not just fire. MMC have offered construction companies the ability to build more affordable and sustainable homes with a lower carbon footprint, but their lightweight nature can make them vulnerable to potential water-related risks. The ability of many MMC materials to withstand the effects of flooding is unknown in many cases.
The term MMC also encompasses manufacturing techniques such as steel or pre-cast concrete frames, panellised units, modular and volumetric buildings, structured insulated panels and timber frames – many of which involve off-site manufacture. These can, if used appropriately, minimise waste, deliver quality architecture, reduce costs and satisfy green energy requirements.
The insurance risks around these building techniques mainly centre on timber frames after significant fires have occurred both during and after construction. This building technique now accounts for 25% of new homes built in the UK, according to the Structural Timber Association. Consequently, the STA has introduced a number of fire safety initiatives in order to improve performance.
However, concerns remain over timber-framed structures, as they are still susceptible to ignition sources such as cigarette ends and boiler pipes, as well as radiation from other fires. And if a large-scale timber-framed building were to catch fire, it would generally not only involve the total destruction of the site involved but potentially nearby buildings as well.
Off-site construction is a growing trend in the UK and now accounts for around 12% of all projects. One method, that of volumetric or modular construction, allows for factory-produced ‘pods’ to be placed straight on to prepared foundations, allowing for construction projects to be undertaken much more quickly. However, problems can occur after completion if the pods at the bottom suffer damage, such as in the event of a flood.
Pods may not be able to be repaired in situ and may need to be removed and replaced, causing disruption to and removal of the surrounding pods and external finishes.
And where component parts are fixed together – notably modules and pods – there may well be hidden voids through which smoke and water can permeate throughout a building, leading to even a small incident causing a disproportionately high loss.
“While there have been a number of positive improvements, such as in masonry and cavity walls, I do think that we have a long history of pre-fabrication in this country, which has failed,” said Simon Hay, Chief Executive of trade body the Brick Development Association.
Dangers of new technology
Some MMC, by their very nature, are new and innovative. For this reason alone, contractors may have no previous experience of the materials and assembly techniques required. This may actually lead to a poorer quality finish – and added risks – than if more traditional methods had been used. There could also be problems in obtaining replacement components in the future.
Question marks, too, have been raised over the fire performance of some of the new, ‘green’ insulation materials used in cladding systems, such as polystyrene, which can increase fire risks.
Fire resistance then must be carefully considered when using MMC – including weighing up the combined properties of materials – with a need for ‘joined-up’ thinking throughout the design, build and maintenance process to ensure that the true risks are recognised.
“The inappropriate use of materials arising from cost and energy performance can be without due regard to the form and function of those materials, longevity and the consequences of introducing them in combination into a structure without taking into account the size of the structure to which it relates as well,” said Colin Prince, Zurich’s Underwriting Manager UKGI Property Lines.
MMC risk is not easy to assess, however. That is why Zurich stays abreast of new technologies and witnesses fire and flood performance tests on materials. For instance, to better understand one MMC recently introduced to the UK – a cross-laminated engineered timber – Zurich carried out a research project with a leading manufacturer of that MMC.
Turning to insurers such as Zurich, who keep their fingers on the pulse of the construction industry by talking to trade bodies and those who know about the latest innovations, can lead to a better understanding of what risks might arise, as well as leaning on Zurich’s expertise of assessing MMC building risks.
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