What You Should Know About Cross-Laminated Timber Construction

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What You Should Know About Cross-Laminated Timber Construction

Engineers and architects are now favouring CLT for projects such as Pavillions, Bridges, Schools, Flats and Office buildings, With having built residences and low-rise commercial structures using dimensional wood framing since the mid-19th century.

Wood was perceived to have significant structural limitations in terms of building height, which has begun to change. When sets of wood boards are glued together at alternating 90°angles, the assembled product becomes very strong. This product is known as cross-laminated timber or CLT. The CLT engineering method made wood available as an option for the construction of mid-rise buildings, with this the “mid-market” for construction, if you will, is where CLT construction could make significant inroads in the coming years.

It won’t stop there though. CLT has already crossed the border between mid-rise and high-rise construction (structures over 11 stories) though architectural and engineering considerations will ultimately dictate how much cross-laminated timber is in a “timber structure.”

Growing Pains

When something disruptive to the status quo comes along, it starts to cause reallocations of capital and labor in the economy. CLT is no different. These reallocations, in turn, often generate intense debates about the net merits of the disruptive process or technology.

More recenltly the goverment has introduced legislation in response to the Grenfell Tower fire which could have unforseen consequences on the growth of CLT in the UK. The legislation prevents the use of any combustible material within the entire external wall of any residental building above 18 metres in height. The result of this is that CLT can no longer be used in external walls of these buildings. 

While CLT in the ban is not merited, it is not a ban on CLT itself and we are working hard with the industry to ensure that this message is clear and understood. The majority of the heavy lifting in CLT construced apartment blocks are in their core, internal walls and floor slabs. Using CLT for this construction is complaint aswell as safe. 

Think of structures being built with non-combustible materials such as metal framed systems but converted to a hybrid structure with floors of CLT on glulam columns and frames, much like the student housing scheme in Vancouver. (Brock Commons Tallwood House).

We are confident in the fire safety of CLT construction, but the industry really does need to support more research and testing to demonstrate this unequivocally. 

With competing perspectives on CLT, the onus is ultimately on a structure owner to decide whether or not to employ CLT construction based on facts, economics, and the owner’s overall value system.

What are some of the advantages and disadvantages of CLT construction?

Advantages of Cross-Laminated Timber

Proponents of cross-laminated timber construction point out a number of benefits to CLT. We have curated them here:

  • Sustainable
  • Easier onsite delivery
  • Faster installation
  • A cleaner, drier construction site
  • No specialised construction experience needed
  • Less expensive foundation (due to lighter weight)
  • Reduced waste
  • Fire-resistant wood construction
  • Better thermal properties
  • Reduces onsite labor by up to 50%
  • Increases project schedule by up to 25%
  • Performing close to Passivhaus standards requiring minimal heating
  • CLT creates long term storage for COsequestered during tree growth

Disadvantages of CLT

Here are some of the current disadvantages as adduced in various sources:

  • CLT is more expensive than steel or concrete
  • Code restrictions on timber building heights
  • Costs of electrical, plumbing and other services can increase (no wall cavities)
  • There can be higher architectural/design costs
  • A higher material transportation cost (relatively few manufacturing plants)
  • Less long-term flexibility (think future renovations)

CLT on the Rise...

As supply and demand for CLT increase, some of these disadvantages may well disappear. More production can drive down costs. More demand means more people with design expertise.

to conclude with the fact that the UK needs to build 250,00 homes a year, if consideration was used to build from CLT it would save over 10 million tonnes of CO2 every year (the equivalent of taking two million cars off the road). and would subsequently drive reforestation.

What remains the same between CLT and other construction materials is that connections need to be made among building components. Learn more about the growing lineup of Simpson Strong-Tie connectors and fasteners for timber construction.

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