Picture credit: Hans-Joachim Kaiser on Unsplash. Picture caption: Mjøstårnet, an 18-storey, 85.4m tall building in Brumunddal, Norway
Architects are warning that the government’s recent consultation on fire safety guidance may put the UK far behind our peers in Europe, effectively making it impossible to build timber towers taller than 11m.
Timber construction is seen as a positive step for carbon sequestration and may be vital in enabling this country to hit (or get close to) our 2050 carbon goals. However, potential changes to Approved Document B (ADB) appear to prevent the use of timber as a load-bearing material or as external cladding.
ADB is the main statutory guidance document in England, created to help with meeting the legal requirements of the Building Regulations 2010 on fire safety. The Health and Safety Executive consulted on the changes between March and early July this year, via an online survey, and now we await the outcome of the consultation.
Some architects are suggesting the changes mean that timber buildings such as The Black & White Building in Shoreditch and Backstage at the Old Vic could not now be built.
The Black & White Building is the tallest fully engineered timber office building in central London. It’s built from a combination of beech, pine and spruce timber, with a slatted tulipwood facade. Although concrete is used for the foundation and lower ground floor, the rest of the structure uses cross-laminated timber (CLT), resulting in 37% less embodied carbon than in an equivalent concrete structure.
The building’s curtain walling is made from glued laminated timber (glulam), with columns and beams constructed from laminated veneer lumber (LVL).
The Old Vic extension is a six-storey structure, composed of low-embodied-carbon European spruce glulam timber and solid timber floors. It has been engineered in a way that means it can be disassembled and reused at the end of its life, something that is much harder in concrete construction. It’s an inspiring, colourful space which expands the theatre and includes a triple-height cafe and bar, a script library and a dedicated writers’ room.
The consultation text states that buildings more than 11m above ground level should not be built using materials that have a classification lower than an A2-s3, d2 (limited combustibility) as load-bearing elements of the structure. Most timber products would not be able to meet this combustibility standard. Previously, this standard only applied to external wall elements in residential buildings above 18m in height.
Under the new guidance, neither The Black & White Building, at 17.8m tall, nor Backstage at the Old Vic, at 19m, could be built. Of course, the text acts as guidance, so there is speculation on how strictly it would be applied.
With Scandinavia leading the way in mass-timber architecture or “plyscrapers” and the UK lagging behind, it was positive to see some excellent examples of timber construction appearing in our capital and, while safety is vitally important, it would be a shame to take a backwards step in our approach.
One positive aspect of the guidance is the proposal to require buildings of more than 18m tall to include evacuation lifts that will fit a wheelchair and accompanying person. This would give disabled people the chance to get out of a building without relying on firefighters – an eminently sensible approach for new tall buildings.
It will be interesting to see what follows the consultation and whether there is an impact on timber construction. From an eco point of view, timber is better than concrete and this could have been an area where we saw many more developments. Let’s hope that this guidance isn’t the beginning of the end for taller timber construction in this country.
Meanwhile, if you need any assistance with the structural elements of an upcoming project, please do get in touch.
