Jonathan Roynon, technical director at Buro Happold, explains how and why a groundbreaking set of new timber design principles are a crucial step forwards for the built environment.
Engineered timber can reduce the whole life carbon footprint of a building by over 50%, and its use is key to the decarbonisation of the built environment. Timber also has the potential to be regenerative if sourced sustainably and can be a much faster method of construction than concrete.
However, the tragic events at Grenfell caused understandable concern around the use of combustible materials such as timber in multi-storey residential buildings. At first, concerns mainly related to the removal of combustible elements from the façade zone of buildings over 18m (including timber), but it soon became apparent that many specifiers and clients were avoiding using timber structures completely.
But with London bringing in a carbon tax and planning systems driving low carbon design, there’s a growing need for low carbon materials. Despite this, timber in the main remains off the table. Low carbon concrete is cited as a better alternative, but this has many of its own issues.
In response to these challenges, Built by Nature, a network and grant-making fund dedicated to accelerating the timber building transformation in Europe and the UK, partially funded The New Model Building project. Its aim was to show that timber can safely be used as the primary structural material in residential buildings and can be fully compliant with UK building regulations. The aim of The New Model Building project was to set a precedent for others to follow and increase the volume of structural timber in buildings.
The resulting model, developed by a cross-industry team of experts, is a groundbreaking set of design principles that demonstrate how to safely use timber as the primary structural material in multistorey residential buildings.
How the design principles came about
It is worth noting that the main barriers for structural timber in the years post-Grenfell were initially compliance, but that quickly led to issues with insurance and mortgage lenders. Their concerns have meant that insurance for timber buildings has become increasingly expensive and difficult to obtain. The real issue was that the insurance market lacked data about how timber buildings would react if they caught fire. Without understanding the potential degree of loss, insurers took a risk averse approach, almost regardless of the technical solutions employed to achieve building regulations for compliance.
As warranty providers are a key part of the insurance process for residential developments, it was felt that a proof of concept that clearly demonstrated a viable route to compliance would help grow the market’s confidence in timber-based solutions. The team therefore made sure this scheme did just that. In this case, it demonstrated compliance with the National House Building Council (NHBC), as one of the major warranty providers in UK housing.
Waugh Thistleton Architects led the development of The New Model Building as an exemplar scheme. We at Buro Happold provided our specialist structural engineering advice, alongside guidance on sustainability. Fire engineers at University College London (UCL) developed the fire principles so that every element of the building, from the structure to the attachment brackets for the façade, would be fire compliant.
The project team liaised closely with NHBC throughout the creation of The New Model Building, so their concerns could be raised and addressed at every stage of development. Thus demonstrating a pathway for individual projects to achieve sign off.
The result is a clear, flexible methodology that covers all scenarios for timber design, including columns, beams and solid walls.
Why is this so important?
The New Model Building design principles provide the insurance industry with the confidence in timber buildings, opening the door to it as a primary construction material. The vision is that the principles will be refined as demand for timber grows, and demand for other more carbon intensive materials (such as plasterboard) diminishes.
Ultimately, we hope all the work by The New Model Building project team will encourage the construction industry to use timber as a core construction material with confidence, in the drive to achieve net zero.
