Once a construction material outlier, mass timber is fast becoming a product that offers flexibility and sustainability in structure construction. Connect CRE recently queried Danny Harrington, Project Management Advisors’ Director of Innovation about this building product.

Connect CRE: What exactly is mass timber and how is it used in construction?

Danny Harrington: Mass timber utilizes compressed engineered wood products in structural building applications. Mass timber products are pre-fabricated off-site into panelized wood assemblies and used for load-bearing walls, columns, beams, floors, and roof construction. Products are formed through lamination with fasteners or adhesives.

Mass timber framing systems come in various types and offer the potential for great flexibility. A post-and-beam mass timber system creates a skeletal structural framework and most resembles historic heavy timber buildings from centuries past. Mass timber floor and wall systems utilize panelized wood assemblies with load-bearing walls and floor panels that can have two-way spanning capabilities. Hybrid mass timber building systems, the most flexible of all, refer to structural systems relying on any combination of wood, steel, concrete or masonry that together harness the best properties offered by each building material. 

The product was invented in Austria and Germany during the 1980s and 1990s and was once a European specific technical building innovation. With its rapid adoption in the U.S., mass timber is gaining popularity as a building material that is proving to be a regenerating versatile alternative to carbon-intensive steel and concrete construction.

Connect CRE: Why is the product becoming more popular?

Danny Harrington: While mass timber is seen as a critical tool for addressing the imminent crises of both climate change and affordable housing, increased global demand for modern residential construction is the primary driver of current and forecasted mass timber market growth.

Mass timber products, specifically CLT, are increasingly utilized as ceilings, floors and walls in residential construction. Regionally, Europe is the dominant market player in the value and volume of manufactured mass timber. Europeans value the enhancements to total thermal efficiency and structural durability that wood-based materials provide.

Mass timber construction also provides an aesthetic appeal with the allowance of exposed wood, a differentiator from the dropped ceiling finishes provided by the traditional construction market. Exposed wood helps building occupants affiliate with the natural world – a biophilic design property that speaks to our inherent needs to associate with natural features and processes.

In addition to residential construction, mass timber is used for commercial and institutional building projects. Space-planning configurations for building programs such as office and education work well with optimized mass timber structural grid layouts. Aligning space modules with mass timber structural modules can help achieve cost and material savings.

Connect CRE: Why and how is mass timber a sustainable material?

Danny Harrington: Mass timber construction provides an opportunity to reduce the carbon footprint of the built environment. It emits less carbon than steel and concrete during the manufacture and construction processes because it requires less energy and generates less greenhouse gas emissions during processing.

Wood building materials also store sequestered carbon that would otherwise be released back into the atmosphere if the trees were allowed to decay naturally in the forest. Removing mature trees and planting new seedlings is a cyclical carbon-absorbing forestry process that results in lower emissions.

Wood is a renewable and recyclable construction material, and wood construction generates less onsite waste and speeds up construction time. Wood also has greater energy efficiency because it exhibits a low thermal conductivity (high heat-insulating capacity), making it a better insulator than comparable building materials. Therefore, mass timber buildings have the ability to be zero-emission, or carbon neutral, but this is predicated on establishing and monitoring sustainable forestry management practices.

Connect CRE: Are more builders gravitating toward mass timber?

Danny Harrington: Many jurisdictions don’t have prescriptive code recognition of new tall mass timber construction types (IV-A, IV-B, IV-C), as specified in the 2021 International Building Code (IBC) code. Despite this, officials in cities like Washington DC (80M Street), Cleveland (Intro), Milwaukee (Ascent) and Boston (11 E Lenox) approved mass timber projects that push the boundaries of what can be built with carbon-sequestering engineered wood. Such forward-thinking attitudes from city officials encourage developers, architects and builders to consider mass timber as an alternative to fossil fuel-intensive concrete and steel.

Forecasts for mass timber market growth predict a 13.6% annual rate of expansion through 2028. Billions of homes need to be built over the next decades to house new occupants in densifying urban centers around the world. Buildings built of mass timber instead of concrete and steel are a viable solution and would prevent huge amounts of carbon from being emitted and warming our atmospheres.