As a well-established methodology for constructing buildings, and with its embodied carbon credentials, it could well be the silver bullet that the industry is after – but it is not without its challenges. Whilst the use of timber has been sky rocketing in the housing sector for a number of years, it is yet to fully take off in the commercial and high-rise housing sectors, with the industry slower to fully embrace the engineered timber solutions available.
What do we mean by “engineered timber?”
Engineered timber is a catch-all term for structural timber products where they have been “engineered” in some way prior to installation. The most common types of engineered timber are:
- Cross-Laminated Timber (CLT) – Also known as X-Lam, CLT is the most commonly used engineered timber product. It is a two-way spanning, prefabricated panel which is used to form environmentally sustainable structural walls, roofs and floors. It is produced by stacking anywhere from three to seven layers of timber, each at 90 degrees to the layer below – gluing each layer to the next with a very small quantity of adhesive (circa 0.6% of the final panel). Manufacturing is done using state-of-the-art CNC (Computer Numerically Controlled) joinery machines, ensuring exceptional levels of accuracy are achieved.
- Glulam – Also formed by stacking sheets of timber on top of one another, but unlike CLT/X-Lam, they are stacked parallel to the grain/each other. The real advantage of Glulam is that it can form very long, continuous beams with an impressive load bearing capacity.
Whilst there are a number of other variations of engineered timber out there, broadly speaking, they all follow one of the two models above – utilising differing numbers of layers of timber stacked on top of one another and then glued together to increase the strength, durability and fire resistance of the end product.
Why use engineered timber in a development?
There are a number of potential benefits to using engineered timber:
- Cost – Whilst the material cost itself can be cheaper, the overall cost of development is often significantly lower. This is because using engineered timber can speed up the overall construction programme and therefore deliver the end product much more quickly; labour onsite can also be reduced, with more of the work being done in factory ready for delivery and installation “just in time” on site.
- Aesthetics – Many architects are extremely keen to use engineered timber in their designs in order to create beautiful, natural and healthy looking buildings.
- Environmental – Perhaps the most obvious benefit; engineered timber contains embodied carbon, meaning it can hugely reduce or even nullify completely the carbon footprint of a building, long into its operational life.
- Weight – In locations where the overall weight and foundations of a building are an important consideration, such as over railway lines or tunnels, engineered timber is significantly lighter than its traditional counterparts, allowing for far more flexibility in building design.
What are the drawbacks?
As with anything, there are some potential concerns and hurdles to overcome when using engineered timber:
- Fire – With wood fundamentally being a fuel, there are concerns about the fire performance of engineered timber products. Huge amounts of research and testing are currently underway to better understand this potential risk. For the time being, concerns remain around the performance of exposed CLT and Glulam during a large fire – not so much for their ability to meet building standards for structural integrity, but more so for their long term, post-fire structural performance and remediation/reinstatement.
- Longevity – Whilst timber has been used as a construction material for millennia, engineering timber products are still relatively new. With buildings being designed for minimum lifespans of 50 or 60 years, no CLT or glulam structure has yet lasted the full test of time, and thus there is a concern around how the products will perform in the long term.
- Capacity – As architects and design engineers look to go higher and higher with timber buildings, there is uncertainty around the limitations that exist with the various products and how their performance may change under larger and larger loads.
What does all this mean when trying to insure an engineered timber building?
At present, there is still a relative lack of knowledge within the insurance sector when it comes to timber – both at broker and insurer level. There is also a lack of hard, statistical experience, meaning insurers have to base their pricing on a limited sample size, and a sample size which unfortunately in the UK does contain some large fire losses. All this makes placing timber risks, into what is already a hard market, much more challenging.
The good news, however, is Gallagher has been working with the Structural Timber Association (STA) for the last 10 years to try and educate insurers. As a result, there has been a sea-change in attitude across all sectors in recent times, with the sector increasingly keen to find workable solutions. In the past 6 months alone, two further cross-industry working groups have been set up to find solutions to building in engineered timber long term. In the meantime, in terms of trying to insure a specific risk, our top tips are as follows:
- Engage us VERY EARLY ON – There is almost no point at which it would be too early to begin the conversation. If it is a building or extension/re-development in design, insurers may want to have significant input in relation to that design – whether it be mandating sprinklers, or ensuring the appropriate separation distances are being planned for. Furthermore, in what is already a hard market, engineered timber risks take even longer to place; with more insurers needing to be involved, and insurers requiring longer to understand the risk. The earlier you can begin that conversation the better.
- Use a broker who understands timber – Hopefully it goes without saying, but there are still pockets of expertise within the insurance sector. Engaging with the right individuals will go a long way to achieving a positive result.
- Work with your broker when presenting information – Insurers by nature are keen to understand the likely worst case scenario – as that is how they calculate their likely maximum loss. The more you can demonstrate firebreaks, fire protection, site management, experience and separation distances (to name but a few elements) the more favourably an insurer can look at the risk.
It would be naïve to say that insuring engineered timber right now is easy; however with the right engagement, collaboration and information, it is certainly doable – and with engineered timber being the obvious material of choice to combat climate change, new solutions are being drawn up all the time.