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Building with Cross Laminated Timber (CLT): Pros and Cons

Building with Cross Laminated Timber (CLT): Pros and Cons

The Rise of a Curious Contender

There’s always some hype surrounding new products that promise savings, sustainability, or environmental benefits. Cross laminated timber (CLT) is no exception. First introduced in Europe in 1994, it quickly gained support as an alternative building material and has grown in popularity in the US.

As someone who genuinely appreciates the beauty and versatility of timber, I have to admit that CLT is one of the nicest building materials I’ve come across. But of course, as with any innovation, there are both pros and cons to consider.

So, let’s dive in and explore the features that make CLT an excellent choice for building, as well as the aspects that aren’t quite as appealing. By the end, you’ll have a clear understanding of whether this curious contender deserves a spot in your next project at timber-building.com.

The Advantages of Cross Laminated Timber

Let’s start with the features of CLT that make it an exceptional choice for building. And I’ll do my best to maintain a balanced perspective, even though I have a bit of a soft spot for this material.

Sustainable Timber Utilization

One of the primary benefits of CLT is its efficient use of timber. The dimensionally small sections required for CLT construction allow for a significant percentage of the harvested tree to be converted into usable lumber. Sections of lumber that would traditionally be discarded as too small now find a purpose in CLT boards. This means smaller trees can be harvested, reducing the threat of devastating forest fires.

You see, tightly packed smaller trees act as kindling, so harvesting them not only fulfills a positive role in fire prevention but also utilizes a material that had no commercial value in traditional logging. The controlled harvesting of lumber also positively affects biodiversity and wildlife habitats, as it allows for a wider variety of vegetation to thrive and provides more sources of food and shelter.

My steel and concrete-loving friends may argue that the true construction time is from when the boards are laminated, formed, and cut to size. But in my opinion, the more important factor is the time saved on the construction site, and in this regard, CLT is undoubtedly much faster.

Rapid Construction and Precision

A crew of four to six skilled craftspeople can install more than 10,000 square feet of building per day using pre-cut CLT panels. The sequence of pre-cut boards delivered in the correct order on the allocated date has an almost idealistic ring to it. Less waste, fewer on-site workers, and faster construction times – what’s not to love?

Furthermore, the tight tolerances required in CLT construction ensure that the joints are airtight or at least tight-fitting, resulting in excellent draft-proofing and significant energy savings. And the solid wood construction helps preserve the internal temperature of the building, reducing the need for insulation.

Structural Strength and Resilience

CLT panels have an exceptional record of surviving seismic events, making them the ideal building material for areas prone to earthquakes. Tests in Japan demonstrated that a seven-story CLT building could survive 14 seismic events without substantial damage. That’s pretty impressive, if you ask me.

The alternating wood grain patterns in CLT boards also produce immense strength and stability, making them ideal for long spans while offering superior vertical strength. And to top it off, these panels perform exceptionally well in retarding the spread of fires, thanks to their self-insulating and charring barrier properties.

Acoustic and Aesthetic Qualities

CLT boards have excellent sound absorption qualities, making them ideal for theaters, cinemas, and other spaces where an echo-free acoustic environment is desired. The tight joints in CLT construction play a significant role in reducing both airborne and impact noise.

And let’s not forget the natural beauty of wood. CLT’s soft, comforting appearance brings the beauty of nature into our living spaces, and the finish is conducive to a variety of interior decorating effects. It’s a win-win for those who appreciate the aesthetics of timber.

The Drawbacks of Cross Laminated Timber

Now, let’s take a look at some of the aspects of CLT that aren’t quite as appealing. As with any innovation, there are always a few hurdles to overcome.

Cost Considerations

At the outset, it’s worth remembering that change is disruptive, and CLT does herald considerable changes to conservative building methods. CLT is still considered an expensive option compared to traditional construction materials.

However, we need to take a holistic view on what constitutes value. Is it only the monetary cost, or should we also consider environmental benefits, employment potential, and aesthetics? If a midsize building uses CLT timber, it could reduce the global warming potential by 15 to 25%. Isn’t that worth something?

Insurer Hesitancy and Code Restrictions

As the popularity of CLT construction grows, insurers are still catching up. The relatively short history of CLT construction sits uncomfortably with insurers, leading to higher premiums for buildings using this material. But as the track record improves, this gap will likely narrow.

Additionally, code restrictions around buildings constructed using CLT are still being evaluated and fine-tuned. This can create some challenges and delays, but it’s all part of the process of introducing a new building material to the market.

Installation Considerations

One of the drawbacks of CLT-constructed walls is the lack of cavities that would typically house plumbing and electrical wiring. This requires careful planning and can have an impact on overall costs, as provision must be made in flooring and ceilings to accommodate piping and cabling.

Vertical panels may need to be routed to accommodate pipes and cables, or an additional light frame partition might be added to house them. This adds an extra layer of complexity to the construction process.

Moisture and Insect Concerns

The moisture content of CLT boards must range between 9 and 15%, and they must be protected from the weather during delivery and construction. Any water absorption by the boards may result in mold and rot, which could compromise the structural integrity.

While the tight tolerances and use of CLT as an internal material help reduce the threat of insect infestations, a recent study found that vacuum-treating the boards with a borate solution is necessary to resist some insect pests, particularly termites. This adds an extra step to the construction process.

Balancing the Pros and Cons

As with any building material, there are pros and cons to consider when choosing CLT. The benefits, such as sustainable timber utilization, rapid construction, structural resilience, and appealing aesthetics, make a strong case for its use.

However, the higher costs, insurance challenges, installation complexities, and moisture/insect concerns are hurdles that need to be carefully navigated. It’s all about finding the right balance and determining whether the advantages outweigh the drawbacks for your specific project.

One thing I can say with certainty is that the more planning and attention to detail you can put into a CLT project, the better. The lesson I learned is that there can never be enough planning in the early stages. CLT construction is all about fitting tight tolerance pieces together, so the more you can prepare, the smoother the process will be.

As for the speed and silence of CLT building progress, they’re more than impressive. The time savings associated with this building material are not overstated, so be prepared for things to move along a little quicker than you might be used to. Just make sure your sequence of erection is critical and takes the stresses of the structure into consideration.

While flexibility in design may be somewhat limited with CLT, it does allow owners to move into the completed house and complete the interior fitting out themselves. So, there’s a certain level of customization and personal touch that can be added to the process.

At the end of the day, whether CLT is the right choice for your next project at timber-building.com comes down to careful consideration of your specific needs, budget, and the overall vision for the build. But with a balanced understanding of the pros and cons, you’ll be well on your way to making an informed decision.

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