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Timber industry responds to height changes

1 June 2020

THE SECTOR gave ‘swift pushback to the government’s decision to lower building height limits in relation to combustible material use, with the new limit of 11m.

The Architect’s Newspaper reported on the response by the sector to the government’s review consultation for the combustible materials ban on external walls of buildings, which it claimed would ‘take an ax to the tall timber trend’ and ‘lop the maximum height of wood-framed residential buildings and hotels from six stories to just three or four’.

The news outlet noted that ‘to be clear’ Grenfell was a ‘concrete slab structure’, and the combustible cladding was ‘the primary cause’ of the fire, stating in turn that ‘due to the use of specialised wood flame retardants and fireproof cladding materials’, modern timber structures ‘no matter their height’ are ‘not viewed as particularly more susceptible to fire than non-timber buildings’.

However, it pointed out that ‘there’s a view that even slightly tall-ish builings’ using structural timber ‘could present an elevated fire safety risk even if a building’s external walls are not wood’, with the new restrictions to apply to wood cladding and structural timber, meaning that any building above the heights outlined ‘would be limited to having wood floors’. This ‘received swift pushback’ from the sector, which ‘has already experienced a sharp decline in England’ post Grenfell.

Industry company Stora Enso’s Matt Linegar stated: ‘Obviously no-one wants to see another tragedy like Grenfell; protecting life is the main concern. But the government is over-reacting. Properly-constructed timber buildings can be safe in a fire – it depends on the design. Even with the current guidelines introduced after Grenfell there has been a chilling effect on the industry. People commissioning buildings think “I’d better not use timber”. The market has virtually dried up.’

The Timber Trade Association argued in turn that limiting the height of timber residential buildings ‘could have a detrimental impact on housing construction, adding: ‘The best way to improve this legislation would be to focus any extension of a ban on combustible materials down to 11 metres on the external cladding, not the structural wall itself.

‘Making such a change to the ban would also bring us into line with regulations in Scotland, which banned combustible cladding above 11 metres, but does not include the structural wall in the scope of the ban. One of the concerns which emerged from the Grenfell Tower fire was how quickly flames were able to spread across the surface of the building. This occurred due to the external combustible cladding and was not related to the structural walls.

‘There is no evidence that structural walls pose the same fire risk as the external cladding, and so there is no justification for treating the two in the same way.’

The news outlet cited the concrete sector’s calls for ‘no U-turn’ on the combustibles ban, and said that large timber structures are ‘viewed as an attractive, highly sustainable alternative to environmentally taxing concrete and steel construction’, the timber said to ‘act as carbon sinks by locking in vast amounts of greenhouse gas’.

Recently, the Royal Institute of British Architects responded to the consultation, stating that the combustibles ban should be extended ‘to prevent further loss of life’, though adding that ‘furtehr research into the use of structural timber within external walls […] should be undertaken to determine performance when subject to real fire loads’.

Last month, timber company Södra stated that a ‘science first’ and ‘fact-based’ approach to the upcoming fire safety bill was required, as timber’s future in construction needs ‘an objective investigation’. This came after the recently expressed views of Willmott Dixon chief executive officer Rick Wilmott, who warned that ‘efforts to eradicate’ combustible building materials post Grenfell risk going ‘too far’, and create ‘huge’ challenges for developers.

More recently, the timber industry revealed plans to spend £500,000 on fire tests over the next 18 months on cross laminated timber (CLT) to ‘prove’ its safety in housing and large building use.

Timber industry responds to height changes