GOING WITH THE GRAIN

envisioning a holistic mass timber future

“I CHECK MY FOREST FIRE MIND AT THE TRAILHEAD OF WONDER…”

YEARS AGO I JOTTED THIS PHRASE DOWN IN MY NOTEBOOK AFTER ENCOUNTERing THE INCREDIBLE REDWOODS AT MUIR WOODS. IN OUR FAST-PACED, FRANTIC AGE OF INCESSANT PRODUCTION, I KNEW THESE TREES WERE LIVING TESTIMONIALS TO A DIFFERENT WAY OF BEING AND THAT MY PERSPECTIVE HAD BEEN PERMANENTLY ALTERED.

“The tree which moves some to tears of joy

is to others only a green thing that stands in the way.”

Though this quote, attributed to the poet William Blake, was made two centuries ago, it is as relevant as it ever has been. Humanity is facing the need to build homes at an unprecedented rate and scale. Our current methods for designing, fabricating, erecting and maintaining our buildings is a major contributor to human-generated carbon emissions, accelerating climate change and its consequences.

Mass timber has emerged as a promising building material at this crucial juncture. These days, one can hardly open an architectural or structural engineering publication without seeing one or several articles related to mass timber within the industry. The excitement around mass timber is palpable and warranted. The increased strength and stiffness of mass timber provides us with the opportunity to design wood buildings taller and with longer-spanning elements than ever before.

Timber is a renewable resource. That is to say, it can regrow within a timeframe relatable to humans. As such, timber offers us the opportunity to re-balance humanity’s relationship between the built environment and the forest. Other building materials, like steel and concrete, are quarried from the earth’s finite crust and their raw, constituent materials taking millions upon millions of years to regenerate. If implemented thoughtfully and holistically, mass timber can help us significantly decarbonize the building industry.

Pondering Blake’s quote further, one can see that it is reductive. It labels us and distills us into two distinct camps: tree-huggers & tree-cutters. Of course, human history is riddled with examples of these two groups being pitted one against the other. Tree-huggers versus tree-cutters.

But I believe that a successful relationship between humans and trees must land somewhere between these two extremes. Somewhere between this dichotomy we can begin to envision a future reciprocity, a mutualism, between the forest and a timber-rich built environment; a world of healthy forests and healthier buildings. But we cannot conceive and build a mass timber world without careful consideration as to how trees and forests thrive.

To help us envision this potential future, I might re-phrase Blake’s quote in the form of a question:

Is a tree a miracle or a commodity? Can it be both?

Trees are the most incredible 3D printers on the planet.

From carbon and sunlight, out of thin air and soil-derived nutrients, they create their biomass through the process of photosynthesis. The architecture of a tree is incredibly honed; no leaf, no twig, is wasted. The physical form of a tree responds to, and is shaped by its local soil conditions and the most efficient pathway to accessing sunlight.

A tree is the original skyscraper.

The cellular make-up of a tree trunk adapts to be stronger in compression or tension based on the resulting forces from prevailing winds.

Tree roots provide structural stability against overturning forces while engaging and retaining the soil in close proximity, preventing erosion.

But trunks and roots, as with every element of a tree, serve more than one purpose. Trunks double as vertical transportation systems with bundles of xylem transporting nutrients between root and leaf. Roots facilitate resource-sharing with neighboring trees, serving as distribution networks.

the form and function of a tree are in harmony.

Though trees are incredibly efficient structures, they retain their aesthetic appeal. Each one is beautiful and mesmerizing on its own accord; limitless in expressiveness and individuality.

Considering this, one could claim that a single tree is a highly evolved, idealized work of natural architecture. And if an individual tree is an idealized work of architecture, then could we imagine a collective to trees to be a metropolis? delving into how forests function, we uncover some remarkable parallels between cities and forests.

In 1997, Dr. Suzanne Simard published astonishing findings in Nature magazine with an article titled ‘Wood Wide Web’. In it, Dr. Simard described the experiments and findings that proved the interconnectivity of trees through underground mycorrhizal networks.

A mycorrhizal network is a dense fungal network within the soil that taps into the roots of trees, connecting them. (Envision something akin to a neural network.) Mycelium is self-proliferating; hyphae at the tips of each mycelial thread reconnoiter, burrowing through the soil, seeking out the nutrients for its own growth and the needs of the trees it connects.

The shear density of the world’s mycorrhizal network is astounding. Estimates claim that between thirty and fifty percent of the living mass of all soil is mycelium. If one were able to extract all the mycelium in the top ten feet of soil on the earth’s surface and stretch it out linearly, it would extend nearly half the width of the Milky Way Galaxy.

Through this network there is a daily and seasonal redistribution of vital resources like phosphorus and nitrogen across different plant species. Mycelium regulates this distribution based on the needs of the tree community. In other words, trees depend on each other and mycelial networks. Thus, the more interconnected trees are to the species around them, the more resilient they become. Biodiversity is a measure of resiliency.

Similarly, a thriving city is one that boasts diversity of people, cultures, economic means, functional educational and healthcare systems, and quality transportation and infrastructural networks. Resilient cities mimic the attributes of resilient forests.

Different tree species grow at different rates. To successfully integrate renewable resources into our built environment, the rate of our timber construction must synchronize with the growth rate of our trees. If we are to integrate mass timber at scale, we need to plan our resources. We need to plant and grow the volume of wood that meets our cities’ current and future needs, which begs the question: what is our current and future demand?

Planning a healthy forest is complicated, especially in the face of rapidly shifting climates. It relies on many interdependent factors: native species, soil health, climate patterns, and biodiversity, to name a few. Nevertheless, this complexity must not paralyze us. Using a few basic assumptions, I will demonstrate that it is indeed possible to achieve a mass timber future while stewarding healthy forests.

At present, the overwhelming majority of species used for structural timber are softwoods: spruces, pines, and firs. And for good reason, they grow straight, tall, and relatively fast. They are abundant in many regions within the United States. Our current fabrication techniques and grading systems are all based on the large-scale usage of these softwood species.

Operating within this current paradigm, consider a fir tree that matures at an age of 80 years. An 80-year-old, 80-foot tall fir tree with a 2-foot diameter trunk will yield approximately 750 board feet of wood. If we understand a tree’s yield, we can compare it to the volume of wood within a timber building and determine the number of mature fir trees that building will demand. Furthermore, if we know the average diameter of the crown of these trees we can determine how many can reasonably fit within one acre of land. If the average crown diameter of a mature fir tree is 25 feet, approximately 70 fir trees can grow in one acre of forest. And if we determine the yield of a fir tree and the volume of trees that can grown in one acre, we can link the volume of timber in our buildings to an equivalent acreage of forest.

A stick-built, wood-framed, single family home of 2,600 square feet will use 16,380 board feet of wood. Applying our assumptions of a mature fir tree, this would require 22 mature trees or roughly one third of an acre.

a sampling of four mass timber buildings that I’ve had a hand in designing range from 6-10 board feet of wood per square foot of building. If we average this range and assume 8 board feet of wood per square foot of mass timber construction, then a 50,000 square foot mass timber building would require 400,000 board feet of wood. At seventy trees per acre, this building would demand 7.6 acres or 533 mature fir trees.

Let’s scale up. In New York City in 2023, 23 million square feet of new construction was permitted in Q4. For the sake of demonstration, let’s maintain this rate of construction. 23 million square feet per quarter is 92 million square feet of new construction in a single year.

If all this new construction were to be mass timber, 92 million square feet at eight board feet per square foot would require 460 million board feet of wood annually; or 14,019 acres populated with 981,333 fir trees each year. This is the equivalent of 16.6 fully forested Central Parks per year.

Don’t get me wrong, that is a lot of trees. But consider this acreage in the context of New York State’s 18.6 million acres of forest. To sustain all new construction in New York City in mass timber, it would require only 0.08% of New York State’s current forests per year. If New York City were to maintain the same rate of mass timber construction for the next 80 years, it would require only 6% of New York State’s forested area over that period of time.

I am making this connection between New York City and New York State’s forests because New York City, given its size, density, and rate of construction, is an extreme example of construction material consumption (an issue which also must be addressed). If we make the case that local or regional forests could conceivably support the rate of construction in New York City, then this a promising model for other cities and their regional forests.

I am aware that this example is a gross, idealistic, over-simplification. The majority of species in New York State are actually hardwoods, not softwoods, and hardwoods are not, at present, commonly used in mass timber production. Furthermore, 60% of New York State’s forests are privately owned. So any scalable solution towards a mass timber future must involve more wood species. It must also involve public and private sectors working in concert towards a shared understanding as to what constitutes proper forest stewardship. Nevertheless, it is reasonable to believe that we could plan for a 6% expansion to New York State forests to accommodate a mass timber future.

The tree species used in our mass timber production should expand include hardwood timber and salvaged or reclaimed wood. It is logical that the wood species in our buildings should reflect the diverse wood species in our regional forests.

For many years we believed that the right way to ‘design’ a productive forest was to plant singular, softwood species in neat rows and use pesticides to kill off any competing species so that a monocultural tree plantation could grow unencumbered — straight, tall and fast.

But forests do not grow this way naturally. Reducing biodiversity makes them less resilient, more susceptible to pests, pathogens, storm damage and wildfires. Presently, there is a disconnect between the design of resilient forests and the timber that we use for the construction of buildings. A built world of softwoods means that our forests would be mono-cultural softwoods. But a built world of mixed species, soft and hardwoods would encourage the cultivation of biodiverse forests.

We can look at past and present indigenous cultures to better understand forestry practices that focus on mutualism rather than extractive measures that solely benefit humans.

Consider the Menominee in Northeastern Wisconsin whose forestry practice promotes biodiversity, tree age, long term growth and yield on their 235,000 acre forest for their community-owned sawmill, which has been operating for the past 160 years. Their forest is FSC (Forest Stewardship Council) Certified.

Their forestry practice was dictated by Chief Oshkosh.

“Start in the west, make your circle by taking only the sick and mature trees, yet, keep in mind by taking care of the other creatures and leaving it as you first came, as so when you make your circle to the point of the start, you then will again have another stand ready for you on your next circle. For it is truly this circle, if we take care of her, Mother Earth, for it is true that she will always be there to take care of you!”

There are now 1.9 billion board feet of standing sawn timber in their forest. This is more than the 1.2 billion board feet that was present in 1854 when the sawmill started. During the 160 years of operation, 2.25 billion board feet of what has been harvested from that same acreage.

Indigenous forest management and stewardship techniques are living examples of success. These strategies are vital for us to adopt in a mass timber future.

At present, our cities do not adequately track the volume of materials coming in or out of their city limits. I don’t mean to suggest that this is an easy feat to accomplish, especially at the scale of a city the size of New York, but if we’re to embark on any sort of design-to-resource synchronization, then we must try. We live in an era of big data, data-tracking, and computational tools. Mapping and understanding material volumes at large scales has never been more possible than it is today.

States, cities and municipalities must begin thinking this way if we’re to envision a future where we can understand and potentially modulate the volume of materials going into our buildings.

Trees alone are not the solution.

We already have an incredible storehouse of materials within the built environment. The unfortunate reality is that most of these demolished materials lie inert or decomposing in landfills while we continue to extract more material from the earth. Collectively, we must value the materials we have already mined and harvested by finding ways to reuse them and by accommodating their future reuse in our current designs with thoughtful configurations and detailing. In other words, we need to embrace and perpetuate an adaptive-reuse-first mentality.

This is not an easy task. We are immersed in a culture that perpetuates a myth of lack and the desire for more and more and more. We extract 90 gigatons of resources from the earth’s crust every year. Our present-day built environment is an architectural manifestation of this myth and mindset.

Who among us will offer up alternative narratives? Narratives that value reuse and enoughness? Who among us will apply our skills and our materials for the benefit of the collective whole, not just the few who can afford more?

The profession of structural engineering can thrive in a world where we devote our expertise to reuse the building materials we already have. And then, only when we must build new, we design our buildings with renewable resources to the extent possible, applying our ingenuity to optimize our designs.

We also need to lead and encourage our architects and our clients to develop elegant design solutions. As Bob Silman, a brilliant pioneer in sustainable engineering taught us: Just because we can digitally model something, doesn’t mean that we should build it. The more important question is Ought we build it?

We are gatekeepers. We produce the structural drawings and models that articulate these designs and the material needs that manifest themselves as physically built works. We have a responsibility to change the impact of our industry on the planet and guide us to low embodied carbon, healthier planetary future.

The implementation of mass timber, at scale, within the built environment is an opportunity for us to look more comprehensively at the current framework of the industry; to examine and question our supply-chains and the value of the material that we use. If every single tree is a miracle, then we must honor its transformation into a structural element and its capacity to shelter us.

No

There is no

this is the way the world is

there is only

the way we’ve imagined it to be

the way we imagine it could be