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Monday, May 20, 2024
Arch-i-text: Wood can be a happy answer to design problems
Brian Marshall says the human invention of mass timber allows engineered wood products to be used in the construction and design of buildings that are strong, less heavy than concrete and more environmentally sustainable.

Driving into the outskirts of Old Town, it is impossible to miss the steel and concrete edifice rising on Niagara Stone Road. 

Now, this is not a commentary on the design – the rendering of which makes it appear vaguely like a temple – but rather the construction method and materials, which impose limits on architectural creativity and expression.

One can make a concrete and steel building look industrial, commercial or institutional and through decorative artifice and elements reduce its inherently cold, brooding and rigid appearance.

Further, a talented architect can create a building from these materials that is impressive, artistic and even inspired.

However, you cannot make it organically inviting nor warm and embracing on an intuitive human level.

Moreover, the cement and concrete industries are one of the two least sustainable industries in the world.

According to a November 2020 report from Princeton University, they produce over eight per cent of overall global emissions and 4 billion tonnes of carbon dioxide (production of each pound of concrete releases 0.93 pounds of CO2) annually.

The highly energy intensive steel production industry isn’t far behind.

The International Energy Agency 2023 publication, “Emissions Measurement and Data Collection for a Net Zero Steel Industry,” reported that, “The steel industry accounts for around 2.8 gigatonnes of CO2 emissions per year, or eight per cent of total energy system emissions.”

There has to be a better way from both a sustainability perspective and for architectural design grounded at the intuitive human level.

The happy answer is look to wood — but, not just any wood as we will see.

So, several decades ago, I found myself just west of Bath, England, as a guest in a house built circa 1100.

The squire, whose family had originally built the house, showed me to my bedroom while apologizing that we had to step over the timber frame members that formed the structural integrity of the building.

But, each time I stepped over those timber beams, my mind asked, “How integral is the timber frame to the survival of this house for over more than 800 years?”

It turned out that, just like Ontario’s 19th-century barns – many of which are still in active use today – a properly designed timber frame with mortise and tendon oak pegged joints is a marvelous structural construct.

In addition, it’s one of the principal reasons for the longevity of many historic buildings.   

That said, our ancestors were surrounded by plentiful old growth forests from which they could harvest long (species dependant, they could be more than 60 feet), straight, strong, old-growth trees.

They are four to six times denser than secondary or tertiary growth with corollary benefits of greater tensile strength, stability, plus fire, decay, insect resistance and more — they were used as logs in their timber frames.

And, while it takes several centuries of species competition in a healthy forest ecosystem to yield old-growth trees, it only took humankind less than 100 years to largely eradicate North America’s old growth forests.      

Thus, by the early years of the 20th century, the majority of the wood available for construction was harvested from smaller and inferior secondary and tertiary growth — wood generally suitable only for stick-framing.

Enter the advent of steel.

Steel suffers from few of the downsides of wood and has a higher tensile strength per cubic space inch occupied.

Yes, it was more brittle and prone to failure during seismic events.

Yes, it was more expensive – and remains so today – than traditional wood construction.

And yes, engineered steel construction limited full architectural expression.

But, it was readily available and a product of the late 19th and early 20th century “way sexy” allure of industrialization.

Given that steel and concrete have been the go-to construction materials for the last 100 years, while the use of available lumber is limited to sticking framing, why would I suggest that wood might be a “happy answer”?

Enter human invention in the form of engineered wood products.

Commonly known as “mass timber,” these engineered products were developed to utilize the inferior wood produced in secondary and tertiary growth forests.

As a group, the products are made from dimensional lumber, veneer or wooden strands that are laminated – generally with glue, but may occasionally be dowelled or nailed – together into “massive” structural elements such as panels, columns and beams.  

The key mass timber products include cross-laminated timber, glued laminated timber, nail-laminated timber, dowel-laminated timber, mass plywood panels, laminated veneer lumber, parallel strand lumber and laminated strand lumber. 

Similar to the manufacture of common plywood – in which strength and stability are engendered through glued cross lamination of multiple layers of processed wood sheets, each type of mass timber product is manufactured through processes which are derivatives of or variations on this theme.

For instance, glulam is made by gluing parallel layers of finger-jointed lumber into columns and beams while laminated veneer lumber is made from glued layered veneer.

Parallel strand lumber and laminated strand lumber are produced from wooden strands impregnated with glue and formed into beams or columns.

Like its name suggests, mass plywood panels are massive sheets of plywood, albeit much thicker (up to 12 inches), longer (up to 60 feet) and wider (up to 12 feet), that can be used for floors, walls, roofs or formed into columns and beams.

Cross-laminated timber, on the other hand, is made by gluing alternating grain direction layers of machine stress-rated, finger-jointed, dimensional lumber into large panels suitable for use as roof, wall and floor assemblies and industrial mats.

Production happens in a factory, and when the manufacturer obtains the engineered building drawings, the dimensions, measurements and so on can be inputted directly into the manufacturing process, thereby producing mass timber components of a size and configuration exactly matching the plans.

This leads to less waste and shortens construction time by approximately 25 per cent.

As a point of reference, mass timber products are not inexpensive, however, the columns, beams and panels, on average, weigh one-fifth the weight of concrete and steel materials, reducing shipping costs and requiring a smaller workforce to install.

Combined, these items (amongst others) and the reduced construction time are significant cost competitive advantages.

Mass timber is fire resistant — generally, well exceeding the fire ratings in North American building codes.

Recent mass timber buildings weigh approximately one-fifth that of comparable concrete buildings, which in turn reduces their foundation size, inertial seismic forces and embodied energy.

High strength-to-weight ratios enable mass timber to perform well during seismic activity.

And, it’s sustainable: according to the U.S. Department of Agriculture, “the near term use of cross-laminated timber and other emerging wood technologies in buildings seven to 15 stories could have the same emissions control affect as taking more than two million cars off the road for one year.”

But, at the beginning and end of the day, wood structures have a biophilic effect on people, increasing occupants’ overall health and wellness.

Moreover, some of the most beautiful recent architecture has been built with mass timber.

So, yes, wood is a “happy answer.”

Brian Marshall is a NOTL realtor, author and expert consultant on architectural design, restoration and heritage.

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