﻿Mass timber building systems are quickly becoming more popular throughout North America as a
sustainable alternative to concrete and steel construction. Wood construction is typically
associated with light wood frames, made of dimensional lumber like 2x4 and 2x6. More than 90%
of American homes are built with these structural members that are usually cut to size and assembled
on-site. Mass timber buildings, on the other hand, are pre-fabricated as a kit-of-parts which
can be erected quickly and smoothly. I made a video on the rise of mass timber
construction and its pros and cons a while back, but this video is going to be a deep
dive into the most popular types of mass timber products. 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?
Mass Timber is short for "Massive Timber", a term for different forms of engineered
wood products that perform as structural elements. They can be 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. 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. 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. A durable, moisture-resistant adhesive is applied to each lamination. Then,
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.
The second is cross laminated timber or CLT CLT is made by gluing three, five, or seven
layers of lumber at right angles to each other. 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.
The third is laminated veneer lumber or LVL LVL is made by layering thin wood veneers and
bonding them together with a strong adhesive. 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. 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.
The fourth is 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. The fifth is 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 like
this train station in Vancouver, Canada. The sixth is 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 and 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. Before we jump into that idea,
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next order with Roofing4US.com. Let’s end this video on the different
types of mass timber by discussing the idea of making the products with reclaimed or recycled
wood.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. Also let me
know if you’d like a dedicated video on their technology. I’m now offering early access to
ad-free videos on Patreon as a thank you to everyone supporting me. I’ll link my Patreon
page in the description. If you haven’t checked out my video on the pros and cons of mass timber
construction, I’ll link it up here and in the description. Don’t forget to hit the like button,
subscribe button and the notification bell too. Thanks for watching. See ya.