At a glance
- Modern methods of construction (MMC) are increasingly common in today’s building designs
- While often offering cheaper, quicker or more sustainable options, new construction methods can also introduce a number of additional risks, both during and after the building phase
- We look at some of the leading MMC and what construction customers should consider when using them
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Modern methods of construction (MMC) can often provide quicker, cheaper and more sustainable ways of constructing buildings. This makes them an attractive solution for today’s designers, and construction professionals are increasingly being introduced to them on projects.
However, MMC can also introduce added risks at the construction stage and require extra precautions throughout a building’s lifetime.
We look at some of the leading modern materials and building methods and highlight the key considerations for customers when working with them.
Timber is considered more sustainable than brick or concrete, making it an attractive option for designers.
However, engineered material, such as cross-laminated timber (CLT), is now enabling timber to be used much more comprehensively, and on much larger projects.
“The obvious issue is that timber burns, and is especially vulnerable during construction,” says Andy Penny, Construction Underwriting manager at Zurich.
“Any increase in the amount of timber needs corresponding increases in fire protection. Designers need to consider fire breaks to prevent the spread of fire should the worst happen. Contractors should also think about compartmentalisation and installation of internal walls etc during the construction stage, large open structures have been shown to be more vulnerable.”
Volumetric, modular and panelised
Advances in pre-fabrication are enabling larger and more complex components to be manufactured elsewhere and assembled on-site. Components can range from wall panels – such as structural insulated panels (SIPs) – to whole sections of buildings, complete with plumbing and electrics pre-installed.
Additional considerations when using MMC:
- As many MMC systems are new and innovative, contractors may have no previous experience of the materials and assembly techniques required
- Using lightweight and combustible materials can cause a greater degree of fire spread
- Modular construction can create hidden voids and cause small problems to result in disproportionately high losses
- Expensive delays can occur if a pod in situ needs to be removed
- The ability of some MMCs to withstand extreme weather and flooding is currently unknown
- There could be difficulty in obtaining replacement components in the future, especially if a particular manufacturer goes out of business
While using these techniques can be quicker, cheaper and more accurate, extra care needs to be taken to avoid large losses occurring.
Modules, for example, are often built using timber and other combustibles, and may feature voids between each module once in situ. While each module should have built-in firebreaks, it is important that these are not compromised.
“Fire breaks are only as good as their weakest link,” explains Andy. “So, if any aspect of the module is altered – for example new services installed by drilling into walls – then it is important that those fire breaks are reinstated.”
Not doing so can allow fire, smoke and water to spread quickly throughout a building, leading to disproportionately high losses. This not only applies at the construction stage – losses can come to light many years afterwards.
Bathroom and kitchen pods
Pods are another modular technique, often used for bathrooms and kitchens. Pods are essentially ready-made rooms, pre-installed with fixtures, fittings and services. Once in situ, they only require basic connections to give a finished result. Pods frequently feature in the construction of hotels, student accommodation and other projects where consistency and cost are prioritised.
However, this perception of ease of use is one reason that pods are a common area of loss. When connecting services, such as plumbing, contractors often choose to do it themselves, and make simple mistakes that a specialist tradesman would not.
“People often think that they can avoid the cost of skilled labour, but you still need somebody who knows what they are doing when connecting them,” says Andy. “For example, forgetting to fit supports underneath waste pipes is a simple, but common, mistake.”
Repairing pre-fabricated, component parts in pods can also be incredibly difficult, or even impossible. Sometimes, the only option is to remove the entire pod and install a new one or replace it with more conventional but bespoke fittings incurring extra costs.
“While they are quicker and cheaper during construction, in terms of longevity and what they cost to repair if there is an accident, some MMC can prove more expensive in the long-run,” says Andy.
Cladding and roofing
With techniques such as Structural Insulated Panels (SIPs) now commonplace for building the superstructure, cladding is often used to give the desired finish, and to protect these vulnerable components from the elements.
Combustibles – such as timber and polystyrene – often feature in external cladding, and there have been several incidents around the world where fires have quickly spread up the side of buildings as a result. It is therefore important to install firebreaks behind cladding, and limit opportunities for ignition or damage – often achieved by commencing cladding from the first floor upwards.
In terms of longevity and what they cost to repair, some MMC can prove more expensive in the long-run.”
Andy Penny, Construction Underwriting Manager at Zurich
Brick slips are another popular cladding system. While resistant to fire, it is important that the correct fixing systems are used to prevent these heavy components falling from the building.
Various pre-fabricated roofing systems are also now available, which can be quickly and easily fixed to make a property watertight. As with cladding, it is important to ensure appropriate fixing methods are used.
“With MMC roofing, wind loads should be given particular attention,” says Andy. “We have seen several instances where the correct fixing specification has not been used by the contractor, and roofs have literally blown off of buildings.”
Working with customers to disclose MMC
A wide range of MMC are now being used in building designs. Each can alter the risk profile of any construction project, so requires the right corresponding risk management action to be taken.
The use of MMC is always a factor that can influence an underwriter’s decision, so it is important that their use is always disclosed. Customers should therefore be clear on whether MMC feature on any of their construction projects, and carry out further investigations if they are unsure.
You can also find out more and access helpful guides and insight with our new Fire Risk Resource.</strong