Mass timber construction on the rise

Wood is gaining renewed popularity as a building material thanks to technological and industrial advances improvements. The reason? Mass timber construction. Research into wood has led to major regulatory changes across the globe that are boosting the use of mass timber in construction projects – expanding its use beyond residential projects to high-rise commercial buildings.

Mass timber can bring many benefits to engineers, architects and designers: reduced reliance on carbon-intensive materials, faster construction times on and off-site, comparable strength to concrete and steel at a lighter weight, and good performance under fire conditions.

Below, we look at timber in detail and tell you what you need to know when planning construction projects with mass timber.

Mass timber is the collective term for a set of industrially produced composite wood products of various sizes and functions. In a nutshell, production involves gluing, nailing or doweling together pieces of softwood —conifers like pine, spruce, or fir, but also deciduous species such as birch, ash, and beech — to form larger pieces with greater compressive and tensioned strength. These mass timber products are produced according to established standards to help ensure customers get the performance they need. Structural engineers, architects and designers then work together to choose the right wood material for their projects.

Main types of mass timber

• Cross-laminated timber (CLT): CLT is well-suited for wall or floor panels as it consists of an odd number of solid lumber boards glued together at alternating 90°angles.
• Glue-laminated timber (Glulam): A structurally engineered and highly customisable wood product. Used for elements such as beams and columns and consisting of pieces of wood bonded together in a layer-cake style.
• Dowel-laminated timber (DLT): An all-wood mass timber product for floor and wall panels. Made of individual laminations held together using wooden dowels. Easy to construct and modify on-site.
• Nail-laminated timber (NLT): Individual laminations mechanically fastened with nails or screws for extra strength. Used for floor and wall panels, its exposed aesthetic lends itself to open-space concepts.
• Laminated veneer lumber (LVL): Vertical layers glued together with composites. Used for beams and columns. Generally made from softwoods, LVL is aesthetically pleasing but less durable.

With more than 70 years of perspective, Hilti has seen many construction trends come and go. But the signs are that mass timber is more than just a fad. Timber construction is expected to make up a 32% share of the construction industry by 2030 – driven by a series of global changes that are converging to place wood a cut above other base materials:

• Climate change: Many countries are aiming to reduce CO2 emissions. Turning trees into timber can mean the emission of fewer greenhouse gases.
• Demographic change: Limited space in urban areas means adding floors to existing buildings is on the rise. Timber is an attractive option here because it is lightweight
• Digitalisation: Digital planning and modelling allow mass timber designs to take advantage of full modularisation. In addition, because mass timber buildings are, by default, prefabricated and assembled on-site, construction time can be significantly shorter. In urban areas where accessibility and construction time can present a challenge when using building materials like cast-in concrete, this shorter construction time can be crucial.

What’s more, the addition of mass timber provisions to international building codes is encouraging developers to explore new ways of using wood in their projects. Countries with healthy forestry sectors like Austria, Sweden and Finland were among the first to adapt their codes and introduce incentives for using mass timber. Others have followed suit. From the Landesbauordnung in Germany to the IBC in North America, standards now direct architects and engineers on how to maximise protection and reach new heights in their building projects. Our wood connection and firestop solutions have been approved for a broad range of applications in wood, based on rigorous testing by European and international standards bodies.

Advocates of mass timber projects cite mass timber’s ability to create a more environmentally friendly construction industry. Research suggests this could be the case: mass timber construction may reduce the global warming impact of buildings by up to 26.5% while the use of emerging wood technologies in high buildings could have the same emissions control effect as taking more than two million cars off the road for a year, according to estimates cited by the US Department of Agriculture. The main benefits include: 

• Lower emissions: As they grow, trees absorb and store carbon from the atmosphere. The wood used in a tall building can sequester vast amounts of carbon.
• Less waste: Wood can be cut and altered quickly and easily into different structures, skins and surfaces – ideal for highly specific, prefab constructions.
• Recycling: Mass timber construction uses a wider array of material quality, and the wood can have a second or third life after being taken out of a building.
• Biophilic design: Timber fits naturally to this design, which helps create healthy, sustainable spaces using elements like atriums, green roofs, and natural light.

Deforestation

Mass timber may be changing the building landscape, but what about deforestation? Some supporters of mass timber argue that strong markets for wood give landowners an incentive to keep land forested. In recent decades, Europe saw a slight growth in net forest area from 1990-2020 while US levels were almost unchanged in that period, according to a United Nations report.

Meanwhile, the European Union says that wood products are crucial in the shift towards a climate-neutral economy. But the EU also warns that the benefits of the use of wood products are unlikely to kick in before 2050. It has also warned that the supply of wood products had to be part of an over-arching strategy for responsible use of global forests.

Fastening in wood construction

A mass timber building is not usually 100% wood. Depending on the application, non-wood materials like steel or concrete continue to play a role.

That’s where Hilti’s joined-up thinking comes in. Our fastening solutions for mass timber construction enable wood-to-wood, wood-to-concrete, and wood-to-steel connections. And the placement of Hilti’s HCW anchor system into the jobsite enables wood-to-concrete fastenings of prefabricated wall panels to concrete panels. It also allows for wood-to-wood fastenings of prefabricated wall, floor and roof sections with a simple “drop and click” hardware connection.

In addition, we offer a glued-in-rod connection system with our HIT-RE 500 V4 epoxy anchor.

Mass timber buildings are highly fire-resistant due to the fire-retardant properties of mass timber, which chars at a slower and more predictable rate while retaining its strength. Nevertheless, fire compartmentation is critical in mass timber buildings as in any other steel and/or concrete buildings, so firestop is an essential part of their design.

To enable fire compartmentation in mass timber buildings, Hilti has invested in an extensive testing programme to verify the suitability of its products in mass timber construction. The focus was to ensure safety, while retaining the productivity of timber construction, including off-site prefabrication. We were one of the first companies to develop listed and certified firestop systems in cross-laminated timber in accordance with ASTM and UL standards. 

Learn more about Hilti Firestop Solutions 

Researchers haven’t uncovered any basic structural or architectural functions wood can’t handle. However, given the precision needed to cut and shape the various components, mass timber can involve several planning challenges.

To unlock the full potential of mass timber, early planning and design are key. With Building Information Modelling (BIM) and prefabrication, construction professionals can achieve higher levels of productivity and accuracy during the construction phase.

To help ensure the success of your projects, Hilti fastening solutions for mass timber are integrated into CAD software solutions. To help bridge the gap between office and jobsite, we offer digital layout solutions for more accurate laying out of points and lines. In addition, we have a wide portfolio of tools for virtually all your woodworking applications.