Mass timber - how to court insurance

With mass timber buildings on the rise, Professor Jim Glockling looks at the impact of insurance considerations and how the newly published Mass Timber Insurance Playbook can help.

One could be forgiven for believing that the provision of insurance is automatic; that the only choice to be made is which insurer gives the best service, value, and free cuddly toy or cinema tickets. Such is the competitiveness within the marketplace you could be forgiven for thinking that, but insurance is not a ‘right’, and in exceptionally rare circumstances something crops up that makes insurers more guarded. When that happens there can be far reaching consequences for all.

In the late 1980s, huge fire losses were occurring in food processing factories and cold stores. The main culprits were polystyrene-filled sandwich panels from which the buildings were constructed, in association with weak regulation in comparison to other countries that did not insist on sprinkler protection, and poor small-scale testing that failed to demonstrate the very different catastrophic fire behaviour that occurred at full scale – delamination. Insurers became wary of such a high level of risk and consequently, insurance became more difficult to get. The solution was an insurer-developed large-scale test for sandwich panels (LPS 1181) that prevails to this day.

In more recent history, light timber frame building has come under similar scrutiny due to extraordinary fire losses both during construction (as the fire resisting layers are the last to be applied), and once built (due to fire spread in voids). The industry has responded with a myriad of control measures, but even now insurance can be punitive for buildings over a certain height.

Now is the turn of mass timber to come under the spotlight. Simon Corbey, Director of the Alliance of Sustainable Building Products describes mass timber as “a generic term that encompasses products of various sizes and functions, such as glue-laminated (glulam) beams, laminated veneer lumber (LVL), nail-laminated timber (NLT), and dowel-laminated timber (DLT).

“The most common and most familiar form of mass timber, and the one that has opened up the most new architectural possibilities, is cross-laminated timber (CLT). To create CLT, timber boards that have been trimmed and kiln-dried are glued atop one another in layers, crosswise, with the grain of each layer facing against the grain of the layer adjacent.

“Stacking boards together this way can create large slabs, up to a 300mm thick and as large as 5.5m long by 30m wide, though the average is something more like 3m by 12m. At this point, the size of slabs is restricted less by manufacturing limitations than by transportation limitations.”

Mass timber is coming more into focus than any other modern method of construction perhaps because of  the types of building proposed to be constructed from it, who these buildings are for, the impact of Grenfell, combustibility and water susceptibility concerns, the novelty of the technology, and the many other sustainability (but potentially insurance-problematic) features now appearing in and on buildings. Mass timber is proposed to replace the prestigious buildings that grace our cities’ skylines – large, serious buildings in which serious things are done for very important companies – a lot is at stake for the insurer if things go wrong.

Whilst the use of mass timber might be for very good reasons in terms of net zero ambitions, insurers must be agnostic in terms of the reasons (good or bad), and just deal with the risk implications presented. It’s a difficult time for many, and it’s not uncommon for mass timber designs to revert to concrete and steel in the face of insurance and Building Control challenges. So, we have moved from a place of familiar building methods, where the owner had a choice of insurer to go to for 100% cover, to a place of uncertainty, where brokers must work very hard to gather limited offered capacity from many insurers to cover the risks – both challenging and no doubt costly. The enormity of the change to timber from concrete and steel cannot be over-emphasised and demands an understanding of the weakness inherent in our building regulations.

Life safety and property protection

In the UK, life safety and property protection are essentially divorced. The life safety compliance objective is generally considered to ensure ‘evacuation before collapse’, but historically it seldom comes to the ‘collapse’ part because concrete and steel are pretty resilient to fire – consider it ‘coincidental’ property protection. If the move to structural timber methods removes the coincidental property protection afforded by steel and concrete, then only additional voluntary measures can make up the shortfall until such time as the UK’s building regulations recognise the need to respond better to mass timber, as well as other forms of modern methods of construction involving combustible structural materials. Without these additional measures, insurers may assume each fire event results in the loss of the entire building, a not entirely foreign situation for thatched buildings and certain commercial classes, but alien for ‘normal’ building types.

In February of last year insurers, through RISCAuthority, produced a white paper highlighting their concerns around mass timber entitled Insurance challenges of mass timber construction and a possible way forward. The document was well received for clarifying the insurers’ stance and laying out the key insurance principles affected. As a new construction method, one that uses combustible and water-sensitive materials and with much research still ongoing, no one can expect insurers to be the guarantor of mistakes made during the learning process – that is the role of research. Where concerns still manifest, however, it demands good in-built risk control features, even if that means compromising on the use of timber, bare or at all, in certain high-risk areas. It may be surprising to know that some insurers consider the potential water-based insurance losses – ingress and escape of water (EoW) – to be more worrisome than those from fire. In the domestic and residential environment EoW losses are incredibly frequent and costly, accounting for more than fire and security losses combined. Now consider this in a multi-storey mass timber building and you soon realise how this might amplify losses still further in the future.

Mass Timber Insurance Playbook

In recognition and acceptance of this, Built by Nature, through the ASBP and in association with Zurich Insurance, Marsh, designers Gardiner & Theobald, and Eurban, commissioned the authorship of a Mass Timber Insurance Playbook (MTIP) which was officially launched in May 2023. This free-to-download guide describes in simple terms the fundamentals of property insurance, and the considerations that the insurer applies to any building presented to them. In doing so it indicates the contribution the designer can make to extending life-safety compliance to include meeting the business continuity objectives of the client and ensuring overall through-life insurability.

Drawing heavily upon the RISCAuthority insurer principles for the protection of buildings from fire, flood, and escape of water, and setting these within the RIBA Design Stages, as detailed in RISCAuthority BDM01 A-Z Essential Principles of building protection, the guide encourages constant attention at every stage to addressing the potential shortfalls in resilience that the use of timber can give rise to. It then recommends applying this alongside meaningful engagement with insurers and brokers throughout. Like any framework it can be applied well or badly, but it offers the opportunity for designers to take forward plans that have gone some way to addressing insurability concerns so that one day a point may be reached where they may be insured on an equitable basis.

Many hurdles still remain. Whilst its publication has been welcomed by most, some designers berate the added intrusion of having to court insurance, perceiving there to be a loss of artistic licence. The perhaps necessary introduction of concrete into areas of specific fire or water challenge can be viewed as defeat by those who want to see 100% timber buildings. That said, the MTIP has already been used successfully to produce a good outcome for the initially rejected design of a school made of CLT to the satisfaction of stakeholders. Hopefully, it will continue to make more valuable contributions to assisting building designers face the current insurance situation.

Fire & Risk Management is the UK’s market leading fire safety journal, published 10 times a year, and is available exclusively to FPA members in digital and print format depending on your requirements. You can find out more about our membership scheme here.

Professor Jim Glockling is a Consultant and the former Director of RISCAuthority.