Wood and civilization

It is easy to understate the importance of timber in the development of modern civilization. Timber is one of the oldest material resources exploited by humankind for so many aspects of its survival and progress ‐ shaping its environment, sustenance, creating habitats, economics, and waging war.

InTechnics and Civilization, historian and philosopher of technology Lewis Mumford expounds upon the qualities of wood that set it apart from any other natural materials, asserting that it is the most fundamental material in the shaping and development of civilization: its role in delivering man

”from the servitude to the cave and to the cold earth itself”, in the tools

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that enabled digging for stone and minerals, its versatility in processing, and its adaptivity to a huge multitude of functions and purposes. Even stone was secondary, according to Mumford: ”Wood, then, was the most various, the most shapeable, the most serviceable of all the materials that man has employed in his technology: even stone was at best an accessory” (Mumford 1934, p. 77‐79). Later on, wood remained a pivotal element in the growing pains of Central Europe, both in terms of its technological potential as well as in the politics of its access and distribution. Joachim Radkau describes the political struggles between those who owned forests and those who lived in and used them. Economics, politics, and wood resources ‐ both as fuel for the furnaces of the mining industry and as a building material ‐ were tightly bound together, especially in the face of wood shortages (Radkau 2012).

In light of this foundational role that wood plays in the shaping of our physical surroundings, it is no surprise to find it in all sorts of corners of society and culture, including language. Linguistically, the wordarchitectand its roots derive from terms associated with wood: ”master builder” in some accounts and ‐ more precisely ‐ ”master carpenter” (Perlin 2005). So does it appear in more recent architectural theory as well: Kenneth Frampton writes that the origin of the term ”tectonic” comes from Sanskrit words relating to carpentry and Auguste Choisy suggests that important elements of the Greek Doric order are direct translations from carpentry principles and methods (Picon 2014). Further in tectonic theory, Gottfried Semper’s prototypical primitive hut is a wood hut, again relating the origins of tool‐making and building to the use of wood before anything else (Semper 1851). In this discourse, tectonics and wood sit in opposition to stereotomics and clay;

filigree and lightness versus mass and solidity. However, as will be later discussed, glue‐laminated timber in fact presents an opposing character: a stereotomic aggregation of wood mass that is carved into highly complex forms.

Wood has driven many building traditions around the world: the stave churches of Norway are an example of enduring Scandinavian wood architecture from many centuries ago (Fig. 3.2); the highly respected Japanese tradition is well known and still finds application today, either with traditional means or with modern reinterpretations using numerically controlled machines and new technologies.

The contemporary usage of wood is still vast and diverse: its use as a source of energy has expanded from firewood to the production of wood pellets for furnaces and power plants; the industrial revolution brought standardized lumber and stick framing traditions for the production of mass housing;

it permeates the household in furniture, utensils, and fashion. Indeed, the presence of wood has permeated all facets of life in all of its different manifestations ‐ from its figure and aesthetics to its utility in building and

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Fig. 3.2:Heddal stave church, Notodden. The largest stave church in Norway.

Photo: Micha L. Rieser toolmaking.

3.2.2 Benefits

The benefits of timber as a construction material are several. As a grown organism, its supply requires only sunlight, water, and good soil. Once cut, forests can be replanted. Properly maintained and with good stewardship, they can be harvested and replenished indefinitely. In contrast to concrete and steel, wood begins its life with a carbon negative footprint, absorbing carbon from the atmosphere through the leaves of trees and sequestering large amounts of carbon in the dense mass of their trunks. This head start over the energy‐intensive extraction and smelting processes required to bring other materials into existence often keeps it ahead all the way to the building site ‐ and sometimes by a very hefty margin, depending on the type and degree of processing along the way (Robertson, Lam, and Cole 2012). Further, the responsible harvesting and usage of timber for engineered wood products provides a greater sequestration of carbon than in unharvested forest stock (Oliver et al. 2014), meaning that the usage of wood in construction has more benefits than simply letting the wood grow.

The easy workability of wood translates into less energy and time spent turning it into a finished product as well as a particular accessibility,

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flexibility, and versatility. Wood is machined with multi‐axis CNC machines in large dedicated production halls, but it is also carved by hand in backyard workshops, or shaped by electric hand tools on the building site. The ease with which trees can be turned into comfortable homes and warm shelters is well known, even in the cold northern climates, as evidenced by building traditions in Scandinavia and North America, for example. If maintained correctly, wood provides a pleasing interior environment and helps to mitigate fluctuations in moisture. Due to its porous cell structure and fibrous mass, it is also a decent heat insulator.

From a technological point of view, advances in material sciences, manufacturing technology, and material engineering have led to an explosion of new types of timber products, new applications for timber in construction, and an increased precision and economy of processing and assembly. Increased precision in industrial processes has decreased the margin of error typically attributed to crafted wood construction and made its structural analysis more robust and predictable (Radkau 2012).

The evolution of timber processing has shifted from haptic and immediate involvement by the workman to an information‐based production which privileges automation and the use of machines to ”replace both physical and intellectual labor” (Schindler 2007). Developments in structural adhesives throughout the 20th century have enabled timber to surpass the limits of the log ‐ important as the older, larger stock of forest becomes more scarce ‐ and use smaller trees or timber stock of a lower quality to produce higher‐quality building products. An example of this is the strong surge in adaptation and acceptance of cross‐laminated timber (CLT) by the building industry (Brandner 2014; Karacabeyli and Brad 2013; Amy Frearson 2015). Developed as a way to utilize lower‐quality timber and otherwise unusable stock, CLT panels are finding a particularly strong uptake in the design and construction of multi‐story buildings and large‐scale housing projects as an alternative to concrete construction.

Glue‐laminated timber is being used as an alternative to steel and concrete construction, and is seeing an increase in formal and technical complexity due to advances in computer‐controlled machining and advanced timber engineering (Müller 2000). New adhesives and lamination techniques have introduced new possibilities, such as hardwood glulams (Muraleedharan, Reiterer, and Bader 2016) ‐ which allow the utilization of new hardwood timber stocks previously left untapped for large‐volume construction;

block gluing ‐ the structural gluing of finished architecturally‐scaled components, exemplified in bridge construction (Aicher and Stapf 2014);

and reinforcement via fibres and other composite means (Romani and Blaß 2001).

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Comparisons to other building materials

Timber and engineered wood products also provide certain advantages over other common building materials such as concrete and steel. Mumford emphasized these, noting that ”wood has the qualities of both stone and metal: stronger in cross section than is stone, wood resembles steel in its physical properties; its relatively high tensile and compressive strength, together with its elasticity” (Mumford 1934, p. 78).

Compared to concrete, timber has a much higher tensile strength, is stronger per unit weight, and has a much smaller carbon footprint: the production of reinforced concrete accounts for between approximately 5% (CSI 2002) and 8% (Rodgers 2018) of the world’s CO₂ emissions. Although the cost of building with cast‐in‐place concrete is lower than building out of wood for mid‐rise buildings, the gap is rapidly narrowing (CKC Structural Engineers 2018).

In comparison to steel, timber is also stronger per unit weight. Construction lumber has a strength of about a tenth of that of mild steel, though at considerably less than a tenth of the density. The greater unit strength of timber means taller buildings can be made lighter. This comes at the cost of more bulky beams and panels, however this increased sizing has a silver lining: the larger cross‐section of timber elements means they are less prone to buckling than steel members of a similar strength.

Also, despite occupying a greater volume than a comparable steel beam, timber members demonstrate a much better performance in fire due to the differing way in which fire acts upon the material. Steel loses the majority of its strength when heated at the temperatures typically experienced in a building fire ‐ about 700‐1000°C ‐ making its failure sudden and catastrophic (NZ Wood n.d.). The charring of mass timber in a fire insulates the underlying wood from the heat, while also depriving it of oxygen, thereby slowing down the rate of burning. The result is that the timber cross‐section retains much of its structural integrity under high temperatures more consistently than steel and for a longer period of time.

3.2.3 Relevance

Today, timber has acquired a new and particularly pressing relevance as a building material in light of mounting concerns about the causes and effects of global climate change, sustainability, and the general health and well‐being of our built environment. Two of the major social issues confronting architects and builders today ‐ overpopulation and climate change (Gopu 2010) ‐ are calling into question the continued usage of high input‐energy materials and their untenable value chains, as well as

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the optimization of material yield and efficiency. More homes and cities must be built ‐ which puts an ever‐increasing toll on the planet’s resources

‐ meaning the effects of material extraction, processing, and usage will be more keenly felt along with the enormous amounts of energy expenditure involved. This seemingly presents a paradox of requiring less environmental impact on the one hand, but more usage and greater exploitation on the other hand. In face of the depletion of oil resources and shortages of aggregate for the concrete industry, more and more focus is turning towards the world’s forests ‐ replenishable, green, and familiar. Wood is seen as

”the steel and concrete of the 21st century” by some (Green 2012; Kunkel 2015), demonstrating its favourable return to the forefront of social and architectural discourse.

Coupled with technological advances in computation, digital sensing, and software‐hardware interfaces, new opportunities arise for the re‐evaluation and re‐conception of existing timber practice and a closer look at recent timber developments in light of these advances. The rise of computation especially allows ”reconnecting the material’s inherent capacities with the characteristics of contemporary design and construction processes”

(Menges 2016, p. 98). These benefits and new technological developments have positioned timber as an attractive, economical, and effective building material in contemporary architectural design.