Cross-Laminated Timber (CLT) – Can It Replace Concrete?
Why Should Builders Care About Cross-Laminated Timber?
Concrete stands out as a vital building material and has been so for tens of years. It allowed us to shape cities effectively and quickly, leading to rapid expansion.
The use of concrete is not debated at the moment whenever building a home, and many other structures. This might change in the future through the use of cross-laminated timber (CLT for short).
Cross-Laminated Timber Vs Laminated Timber
Laminated timber is manufactured through joining boards so that one structural unit is formed. The unit can be straight or curved. However, grains always have an alignment towards one direction.
CLT manufacture involves stacking boards in layers that are perpendicular. This makes it possible to manufacture surfaces or plates, including walls.
We are practically talking about plywood that is made out of boards. This can lead to large dimensions:
- A height of 2.4 meters to 4 meters.
- A length of up to 12 meters.
CLT’s Environmental Impact
Cross-laminated timber was initially manufactured in Austria. The goal was to reuse timber of a lower value. Nowadays, wood is again being used in constructions. This is mainly due to environmental factors.
The footprint that concrete has is huge when we compare it with wood. Creating one cubic meter of concrete leads to 1 ton of carbon dioxide being released in the atmosphere.
CLT includes sequestered carbon, which is practically carbon that is naturally stored inside the wood during the growth of the tree. Due to this, although a lot of energy is used during manufacture and extraction, wood construction has lower overall emissions.
The Concrete Of The Future
Cross-laminated timber is often mentioned as being the concrete of the future because it delivers at least the exact same structural strength that reinforced concrete has. However, the material is more flexible and needs to go through greater deformations in order to collapse and break.
An important thing to note is that one cubic meter of concrete has a weight of around 2.7 tons. The same value of CLT only weighs 400 kilograms and has the exact same resistance.
CLT And Fire
Fire advances at a rate of around 0.8 millimeters per minute in timber. When looking at a CLT wall with a thickness of 100 mm, the material is consumed after 2 hours, even when untreated.
The main cause of death when a fire happens is smoke. It moves from a room to the next through open spaces appearing as different materials converge. When correctly built, CLT is completely airtight.
Due to the airtight advantage, as you built with cross-laminated timber, you have to properly select all the elements that create the structure, like sales and fittings. The majority of the strength that CLT has comes from joints and fittings. Just 10 percent is linked to timber.
CLT And Environmental Conditions
With CLT we do talk about wood and its natural enemies are weather and moisture. The exposed timber suffers. CLT is practically a structural component so we need to properly protect it against corrosion, collapse and wear. Supplementary coating layers can be added, like brick, stone or fiber cement. However, preserving the exposed CLT is possible through other ways.
Mineral paints and vegetable oils help a lot when applied once every 5 years. They actually offer guaranteed protection of up to 25 years against discoloration and detachment.
Mineral paints are great for outdoor exposure and vegetable oils are suitable for indoor use. Such products are odorless and can easily be applied by any person, including the homeowner.
Really Fast Building
If a home is built with the use of cross-laminated timber, everything is predetermined and decided right at the factory. On site adjustments cannot be made. CLT practically behaves with very high precision, just like with furniture. The margin of error is of just 2 millimeters.
With this in mind, projects take longer to draft but assembly is very fast. With just 4 people, a CLT house of 200 square meters can be assembled in just 5 days.
CLT construction and design are guided by specific regulations. These are similar to what is now used when building with laminated timber and concrete.