Ban must not impact UK’s Timber construction leadership27 March 2020
In making the building sector more risk averse on use of wood, new regulation on use of combustible materials in and on external walls risks turning the industry off environmentally beneficial engineered timber-based construction, says Anthony Thistleton of architects Waugh Thistleton
The government has recently released its “Review of the ban on the use of combustible materials in and on the external walls of buildings”, which proposes to extend the ban to a wider range of buildings and to lower the height at which the legislation applies – from 18m to 11m.
This brings it into line with the Scottish regulations in terms of the height, but it excludes an alternative route to compliance via testing.
While we support the principle of a ban on combustible materials in the facades of tall buildings we do not think that the current ban is effective in reducing the risk of fire spread across the outside of buildings, which is its primary purpose.
A blanket ban requires exemptions, as is the case in this legislation. However, these are largely made on the basis of expedience and cost, in that compliance would exclude an economic element, such as PVC windows. Furthermore, the legislation excludes materials that are safe and are not part of the facade, such as CLT.
This is damaging for two key reasons: by allowing certain combustible elements, it implies that these are safe, which is not necessarily the case and could lead to facades that do not adequately resist the spread of fire.
It also implies that materials that are proscribed under the ban are inherently unsafe, which is also not always the case.
The only way to ensure safe building facades is by imposing a total ban on all combustible materials, unless verified by specified testing. This levels the playing field across all materials and elements and ensures that the construction build-ups we employ are fit for purpose and fire safe.
The growing use of CLT over the last decade has been an exciting development offering the construction industry a way to signifcantly reduce its CO2 emissions: the timber itself is a carbon store, having absorbed CO2 during growth; CLT and glulam can be used in place of concrete and steel, which have a very high level of embodied energy and, more crucially, a move towards the greater use of timber will drive demand, and therefore supply, which will lead to large scale reforestation.
The timber industry and, in particular, the use of CLT, has suffered a significant impact from the unwarranted negative perception created by this legislation and a number of developers are now moving away from CLT as a result, not just in buildings covered by the legislation.
The UK has been an acknowledged global leader in the adoption of this building technology over the last decade, which supports innovation, economic investment and employment. The loss of leadership could have a significant impact on these benefits.
It is essential for the safety of the occupants of tall buildings, for the fight against climate change and for the delivery of housing, jobs and economic growth in the UK, that the legislation be properly drafted to address the actual risks and not unreasonably exclude and discredit mass timber.