How is Cross-Laminated Timber Made?

How Are Cross-Laminated Timber (CLT) Wall and Floor Panels Manufactured?

Foreword by Ian Thompson, Editor

Today’s video takes us on a tour of a factory situated in the northern region of Victoria. The factory, owned by XLAM, leverages locally grown softwoods for the production of cross-laminated timber, also known as CLT.

Cross-laminated timber has been gaining recognition and popularity worldwide as a high-performing, eco-friendly structural material. Initially developed in Europe, and some 50+ years later, it has made its way into the architectural practices of Australia and North America.

In this tour, we will delve into the process of cross-laminated timber panel production, guided by Tyson Infanti, from CLT supplier XLAM. Tyson will be explaining the intricate details of this layered wood product, its versatility in terms of size, and the way it is cut and prepared for site use.

We will then explore the manufacturing process. A dedicated and skilled workforce maintains a safe, highly coordinated environment to ensure the products are ready for use in commercial and residential building projects.

We will walk you through the initial stages of sourcing wood sections, moisture content scanning, and the finger-jointing process, which enables the production of long boards from feedstock of any length.

Quality and safety assurance is a crucial part of the process as well, and Colin Stone, the Quality and Safety Manager for XLAM Australia, will shed light on their rigorous testing procedures.

Later, we will explain how the planed and cut boards are assembled into a panel, discuss the adhesive bonding and pressing processes, and finally, show how the CNC machine adds the finishing touches, cutting out windows and door openings.

We will also highlight additional services offered by the factory, including pre-coating with a moisture barrier, lining with a water-resistant membrane, and delivering panels in perfect condition.

So, let’s delve into the world of cross-laminated timber and discover how this sustainable building material is made.

Unveiling the Craft of Cross-Laminated Timber (CLT) Manufacturing

Video Transcript

Today we’re at a factory in northern Victoria that uses locally grown softwoods to produce cross-laminated timber. Let’s go and see how it’s made.

Cross-laminated timber or CLT is quickly growing in popularity around the world. While the product was first developed in Europe, recent years have seen Australia and North America quickly adopt the high performing and environmentally friendly structural material.

I asked Tyson Infanti from a local CLT supplier to explain the product further. “So cross-laminated timber is part of the mass timber family. So it’s a panelized system made up of multiple layers of boards. You can see the multiple layers here. This is a three-layer panel. In each subsequent layer, the boards run 90 degrees to each other.

So with an odd number of boards, we can make up a range of three, five, seven, and nine-layer panels. And with that, we can make 60 mil panels all the way up to 350 mil panels. In terms of the actual format or the size of the panels, we can make up to 16 meters by three and a half meter panels. And then they’re cut up into the sort of the final panels that would go to site.”

So now we know what we’re talking about, let’s take a closer look at how it’s made. Like all engineered wood products, cross-laminated timber is manufactured in a safe, highly coordinated factory environment. Here a workforce of dedicated and skilled staff monitor production and test product to ensure the highest quality output possible.

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The manufacturing process starts with rough sawn wood sections. These are most commonly untreated structural softwood, but treated softwood and even hardwoods are now possible. Different thicknesses of cross-laminated timber panels may require different layups comprising boards of varying thicknesses. For this reason, cross-laminated timber producers must plan ahead to ensure they have the right feedstock for a project.

Once the specified boards have been sourced, they are loaded onto the production line where they are first scanned for moisture content before proceeding to the next station. Here the boards go through a finger-jointing process to create a single long board out of any feedstock length. This means that even if the factory only has two meter long feedstock, it can still produce a panel of 16 meters in length.

The finger joint owes its name to its form, which looks similar to two hands with fingers entwined.

To create this join, both ends of each board must first be cut into the zigzag profile which fits snugly into the profile of the corresponding board. One of these profiles then receives a thin layer of high strength glue, and the two zigzag profiles are pressed together under force to create an immediate bond.

The newly finger-jointed board can be cut to the exact length required and is left to rest in a large storage rack to allow the glue bond to cure.

“My name is Colin Stone and I’m the Quality and Safety Manager for XLam Australia, and this site specifically. Our testing is from the infeed feedstock, with finger joint feedstock into lamella. We’re constantly monitoring the pressure, the glue application. We take finger joint samples every shift and test those against the standards. Through the whole process, we’re doing quality checks to ensure that the end product is within specification.”

Once secured, the long boards are mechanically planed on all four sides to the exact section size required for the panel layup. While this planning process can occur at an earlier stage, completing this process just before the cross-laminated timber panel is assembled ensures a clean fresh surface for the adhesive to bond to, making for a reliable product.

Cross-laminated timber is produced as a rectangular panel, and as it features boards running in two directions, it is necessary to produce both long and short sections. For this reason, once planed, some boards are transferred to another cutting station which cuts shorter lengths. These boards are then transported by conveyor to the panel layup area.

With all boards now planed and cut to size, the panel layout process can commence. This process can vary; however, all manufacturers follow the same basic steps. The first layer of boards is laid on the platform and tightly packed together to minimize any gaps.

When ready, a layer of adhesive is applied and the next layer of boards is stacked on top of the first, this time in the perpendicular direction. This gluing and stacking process continues until the total number of layers is assembled, at which time the panel is transferred to a press.

Here we can see a mechanical press being used; however, other types of press may be used depending on the supplier. Depending on the panel thickness, press type and adhesive used, this pressing process can vary in duration. A typical panel and mechanical press, shown here, takes 25 to 30 minutes to complete the pressing and curing process. After this time, the pressure is reduced and the panel is transferred to a holding bay for processing.

With the master panel now pressed, it can proceed to the CNC machine. The CNC uses the digital design to cut out openings and smaller panels, pre-drill holes, and complete any other fabrication. These robots feature a head that can rotate in up to 11 axis, and can select from a range of cutting, drilling or chasing tools to process an element as per the design. CNC machines take the human error out of the cutting process, resulting in very tight tolerances and a perfect fit on site.

The CNC cuts multiple samples from every panel which then undergo rigorous testing. Every single bullet is checked for glue line durability, dimensional tones moisture, and nothing leaves the site until all the checks and balances are done. Once processed by the CNC, panels are stacked in order, ready for delivery to the job site at the agreed time. Panels leave the factory with lifting straps pre-installed, streamlining the on-site installation process.

Here we can see a prefabricated stair produced from a thick 8-layer CLT panel with treads and risers than cut out by the CNC machine. As with all timber construction, these panels will be installed using only screws and brackets, making for a safe, quiet site.

Where required for the project, a cross-laminated timber supplier can typically offer to add value to the panel prior to delivery. At this factory, panels can be sanded, pre-coated with a liquid moisture barrier, and lined with a breathable water resistant membrane. The final step before delivery, panels are packed and covered in a UV and water resistant sheet to ensure they arrive on site in the same condition they left the factory.

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