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We are about to witness the next big evolution in the construction of buildings—a true innovation that will protect the environment, create jobs in the timber industry, and save residential builders time and money. This revolution is the use of a building method called CROSS-LAMINATED TIMBER, (CLT), aka, MASS TIMBER. In mid-rise buildings (up to 18 stories), this will replace the now common, environmentally taxing, steel and concrete structural methods. In this blog I will talk about the big picture differences between traditional steel and concrete methods vs. the new CLT method.
Explore this follow up blog post regarding the global uprising of CLT and stay tuned for future posts on the manufacturing and installation of CLT.
What’s wrong with steel and concrete?
The production of steel and concrete causes grave disruption to nature. Apart from the pollution created through the manufacturing of the product, it is also time-intensive and noisy, creating an imbalance to its surroundings.
Foremost, steel and concrete are highly carbon intensive in their manufacturing. Steel is mined, heated to high temperatures, and requires much on-site welding. Concrete is bonded by Portland Cement which demands huge amounts of natural gas used to heat it to extremely high temperatures.
Concrete and steel are heavy, which require stronger seismic considerations, especially as you get to the higher stories. When complete, steel buildings are fixed, making it hard to alter for future uses. To find out more about carbon emissions in making cement, click here.
Photo courteous of APA-The Engineered Wood Association
What is Cross-Laminated Timber construction?
Similar to traditional building construction, Cross-Laminated Timber is composed primarily of posts, beams, and horizontal flat surfaces. However, instead of steel columns and beams with concrete infill at floors and roofs, CLT is all wood. Posts and beams are composed of small wood members laminated together. These types of beams are commonly known as Glulams and have been used for decades.
The greater difference between traditional construction methods and the CLT construction is the walls, floors, and roofs are comprised of wood panels. CLT panels are made of layers of lumber boards that are stacked crossways at 90 degree angles and glued into place. The result is wood panels typically three to nine inches thick and up to 9 feet wide by 80 feet long.
Why is CLT such a promising alternative?
Comparatively CLT or Mass Timber has the following attributes:
Wood sequesters carbon. CLT manufacturing requires only small diameter (young) trees, about 10 inches in diameter. These grow fast and absorb carbon as they grow.
Mass Timber buildings are 30% lighter which makes a big difference seismically, especially on upper floors.
Since panels can be delivered pre-cut, the assembly is faster, requiring smaller crews and fewer deliveries.
There are other advantages to this method of construction such as fire resistance and pre-finished surfaces:
The entire design from production to completion is quicker than alternative materials and because of its design it will save builders time and create possibilities for more custom design work. The panels come to the site pre-cut and even pre-finished, expediting the time it takes to prepare materials for installation. The panels are cut on a CNC mill based directly on the pattern drawings produced by the architect. Since the CNC mill can handle cutting complex geometry with ease there is little cost difference. This helps open up new design possibilities including creating custom patterns, contoured window openings, and changing thickness along a wall section. The best part is that it’s made from wood all the way through. This makes the CLT method both cost effective and aesthetically pleasing. You can read more about North America’s largest timber building construction here.
An Owner’s Representative can be a critical facilitator in the construction process from the beginning stages of planning to completion of the building. Having an intermediary with ample experience ensures that the desires of the occupants, as well as sound decisions around construction materials and functionality of the building, are well communicated. With the many teams involved in a construction project, including the contractor, architect, builders and design teams, hiring an Owner’s Representative allows you to have one point person, making the project more successful and pleasant for its future occupants.