Paul's Column: A ban on engineered timber in construction would be based on politics, not evidence

09 April 2019

If the answer used to be Norway but last year became Canada and is now Norway again, what was the question?

Could it be something to do with snow, or ice hockey or reindeer?

No, try again.  Forests?

Very good, you’re almost there.

Norway is once again home to the world’s tallest wooden building. Mjøstårnet in Brumunddal stands at 85 metres tall. Congratulations to Norway, taking the accolade away from Vancouver’s 53 metre high Brock Commons Tallwood House student residence at the University of British Columbia.

With structural strength comparable to concrete and steel, these engineered timber buildings are a double win in the battle against climate change.  Between them the manufacture of concrete and steel are responsible for 15% of global carbon emissions hence a reduction in their use is desperately needed.  Conversely, wood sequestrates large amounts of carbon locking up CO2 in engineered timber buildings for generations.  Furthermore, the planting of new trees to maintain supply generates further absorption of CO2.

The UK has been at the forefront of the application of engineered timber with the world’s largest wooden building (not tallest but the most wood in a building) completed last year in Hackney, London and designed by timber architect specialists Waugh Thistleton.  UK architectural firms are well placed to lead the timber charge against climate change.  While engineered timbers are not yet made in the UK several initiatives are underway which could see this change soon, for instance the Centre for Offsite construction and Innovative Structures within Edinburgh Napier University are testing a prototype hardwood Cross Laminated Timber (CLT) made from UK beech with a view to industrial production somewhere in the UK, hopefully in the North East.

However, these potential new green jobs and the significant reduction in carbon emissions they could help deliver are under threat due to the fall-out from the horrific Grenfell Tower fire of 2017 that caused 72 deaths.  It is clearly beholden on all the relevant authorities to ensure that such a horrendous fire never again occurs in a high-rise building. Lessons are being learnt from the main enquiry and other separate investigations but are the right conclusions being drawn?

One piece of work commissioned by the government was The Independent Review of Building Regulations and Fire Safetyby Dame Judith Hackitt. The report identified many failures in building procurement and the responsibilities of key members of design and construction teams. She made many recommendations but was explicit that banning materials was not the remedy.

Notwithstanding this, the government launched a consultation on banning combustible cladding on residential buildings above 18 metres.

A proposal that timber, or any combustible material, would not be used on the outside of tall buildings above a certain height seems a sensible conclusion especially given the fire at Grenfell travelled up the outside of the building and re-entered the building at a higher level and in this way the fire avoided detection but still spread.

However the ban has now been implemented and includes the entire external wall, which precludes the use of CLT in this area. Not only is this not merited, it is clear that the ban is based on politics, not evidence.

By restricting the use of CLT there is an implication that CLT construction is less safe, which is absolutely not the case.

Massive engineered timber panels form a char layer if they catch fire which protects the rest of the wood. Large format, solid panels are very effective at preventing the spread of fire between rooms, and from rooms to the outside.

It should be noted that Grenfell Tower contained no engineered wood rather it was a traditional 20th century concrete and steel structure. It is also notable that the spread of fire to the outside of the building was via the PVC windows, which can still be used as window frames and are excluded from the ban.

Rightly there is a very high level of sensitivity around the construction of tall buildings in the aftermath of the Grenfell Tower fire but to successfully tackle climate change and maintain fire safety we cannot afford to dispense with a key component - engineered timber – especially if the arguments for doing so are flawed.

Do you think the North East needs its own voice in the EU exit negotiations?

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