What are the most popular Mass Timber products?

May 16, 2023

63 views

5 min read

Mass Timber Products are quickly becoming more popular throughout North America as a sustainable alternative to concrete and steel construction. How can we use nails, glue and dowels to make these massive wood panels that hold up skyscrapers? Can we even use recycled wood to make mass timber instead of sending it directly to landfills?

Introduction

Wood construction is typically associated with light wood frames, made of dimensional lumber like 2×4 and 2×6. More than 90% of American homes are built with these structural members that are usually cut to size and assembled on-site. Instead, Mass Timber buildings, are pre-fabricated as a kit-of-parts which can be erected quickly and smoothly.

Mass Timber is short for “Massive Timber”, a term for different forms of engineered wood products that perform as structural elements. They are made of douglas-fir, spruce-pine fir and western hemlock.

Since wood products are 50% carbon by dry weight, mass timber buildings can store carbon well into the future. Additionally, they have a lighter environmental footprint than energy-intensive materials like steel and concrete. They can also decrease foundation costs and reduce transportation emissions because of their lighter load. Finally, the biophilic qualities of exposed wood can even improve occupant well-being. There are several types of mass timber products. Let’s begin with the most popular type.

Glued Laminated Timber or Glulam

Glulam is made by gluing together three or more small pieces of lumber, typically 2 to 4 inches in width. Individual pieces of lumber or laminations are laid out with the grains running in the same direction, parallel with the length of the member. Then, a durable, moisture-resistant adhesive is applied to each lamination. Later, the laminations are clamped together with a hydraulic press until the glue has cured. Glulam is a strong, versatile material that can be used for roof and floor systems, beams, and architectural features. They can be straight, curved, arched, or tapered.

Cross Laminated Timber or CLT

CLT is made by gluing three, five, or seven layers of lumber at right angles to each other. First, the panel is placed into a hydraulic press and compressed under high pressure to ensure that the glue is evenly distributed and that the panel is tightly bonded together. It is then trimmed to its final dimensions, sanded, stained, or coated with a protective finish. CLT is used as an alternative to concrete to form the walls, roofs, floors and ceilings of a building, bridges, and other structures. It can be pre-insulated, left exposed for its aesthetic appearance or even encapsulated.

Laminated Veneer Lumber or LVL

LVL is made by layering thin wood veneers and bonding them together with a strong adhesive. First, logs are debarked, steamed and peeled into thin sheets, or veneers, 1/16th to 1/8th of an inch thick. Layers of veneers are stacked and a strong adhesive is applied. The panel is compressed at a high pressure and temperature to activate the adhesive and bond the veneers together. Finally, the finished LVL panel is then trimmed down and any rough edges or defects are removed. LVL is often used for concealed beams, trusses, planks and rafters where strength and stability are critical.

Dowel Laminated Timber or DLT

DLT is made with stacked dimensional lumber, fit together with hardwood dowels made of beech, maple, or oak. Dowels are inserted into pre-drilled holes and a hydraulic press forces the dowels to interlock with the boards, creating a strong, rigid panel. DLT is the only all-wood mass timber product with no metal fasteners, nails, or adhesives. It can be used for walls, floor and roofs in offices, schools, commercial and public buildings.

Nail Laminated Timber or NLT

NLT is made by stacking boards and inserting nails or screws at an angle. Any excess nails or screws are trimmed, and the panel is sanded and finished to create a smooth surface. The manufacturing of NLT does not require any sophisticated or expensive machines for gluing or pressing. It is simple and relatively easy to assemble. NLT can be a cost-competitive alternative to cross-laminated timber but it is more labor- intensive. NLT can even be bent to form beautiful curved roofs.

Parallel Strand Lumber or PSL

PSL is made from long wood strands that are bonded together with adhesives and heat. Logs are debarked and cut into long, thin strands 1/8 inch thick. Layers of veneers are stacked, a strong adhesive is applied and the panel is compressed with a hydraulic press. PSL has a rich, warm texture with dark glue lines. It can be made with waste materials from plywood and LVL production. PSL is used for long-span beams, heavily loaded columns and large headers where high bending or compression stress is required.

Even though mass timber has its limitations and shouldn’t be used for every building, it is a promising alternative to energy-intensive materials like concrete and steel. Wood is a renewable resource. It can be regenerated with sustainable forest management practices. What if we could make mass timber even more sustainable by using reclaimed and recycled wood instead of virgin wood?

Urban Machine

Urban Machine is a startup in California that uses robotics and AI to remove nails, screws and staples from old growth, reclaimed wood to turn it into premium lumber products. They are on a mission to divert the 37 million tons of wood waste sent to landfills every year and turn it into glulams, CLTs and other mass timber products. Their automated process could also drive down the cost of mass timber construction. If you’d like to learn more about the Urban Machine, check out my podcast with their CEO, Eric Law!