Wood stock: the many lives of lumber
Softwood lumber is treated to extend its lifespan in use, but it has many other lives.
In the quiet of Covid-shuttered economies, we could hear the hammering of new garden decking. As homeowners built outwards, seeking more outdoor space and something to do, the decking industry celebrated unexpected gains, lumber prices shot up and lumber stocks sold out.
Deck material choices present a complicated assortment of lifespan predictions, aesthetic promises and price tags: will it be pragmatic and affordable pressure-treated softwood, domestic decay-resistant cedar or redwood, a pricey imported tropical hardwood or a recycled plastic lumber or composite? Within each of these choices is a tangle of ethical dilemmas and contradictions at multiple sites and scales: from forest exploitation to material durability to chemical toxicity.
When it comes to decks, we anticipate rapid decay and replacement. Decay is a basis of life on Earth, but in deck-terms, it is bad news. While a house might last for generations, a deck might last a decade or two.
Even before it becomes structurally compromised, a deck is obsolescent if a user doesn’t like the way it weathers. In home renovation culture, decks are outdoors and visible, and allow curious neighbours to take stock and imagine what might be happening inside.
It is this legible, rapid turnover of the everyday deck that draws our attention to the wasteful (il)logic of the cycles of material use in mainstream architecture, landscape architecture and design.
Decking expiration dates are coded into how materials are sold, discussed and popularly understood; from the moment of specification, these materials are already conceptually landfilled.
Beyond hypothetical years of ‘service life’, and all the good times it may support, are other temporalities through which this material should be understood: how tree plantations speed up tree growth and wood production, how wood preservation methods slow down or arrest biological decay, how chemical preservatives persist indefinitely in landfills and organisms, and how all of these time-shifts relate to cycles and concepts of waste and waste-deferral.
Chemically preserved or pressure-treated (PT) softwood makes up more than half of the massive industry of deck materials. It is affordable, reliable, domestically produced and ubiquitous.
Identifiable to even amateur deck-builders, PT lumber is recognised by a tinge of green or brown – and these are shades that have changed with chemical evolution. It is wood, but not only wood. In the US, commercially available PT lumber is likely to be Southern Yellow Pine – a category, not a species. SYP, in lumberyard parlance, is a category of grading and use, whose name joins three disparate things: a general region of the US, a visual characteristic and the common name for a genus (Pinus).
As if there was a word between ‘cow’ and ‘beef’, SYP specifies both ecological entity and fungible commodity, while generalising at the same time.
‘According to this framing, not cutting wood was wasteful, and discouraged the forest from reaching its productive potential – slow growth was waste’
An SYP board is likely to be one of four species: loblolly, longleaf, shortleaf or slash pine. Prior to the mid-20th century, longleaf pine’s straight and dense wood – slowly maturing in old-growth forests – was prized as strong framing lumber, but old-growth trees were quickly over-harvested. Today, it is the fastest growing of the SYP pines, loblolly pine, that dominates the label.
Loblolly pine grows quickly in plantations and can survive in poor, sandy soils, and its speed and ability to grow like a weed, quickly and in non-ideal conditions, makes it a popular, profitable choice for both large and small growers.
The SYP appellation emerged in 1915 to establish common grading standards, but it also served to further abstract a builder’s relationship to the specificities of wood species and the landscapes that they come from. With this new name, multiple species (and their distinct growing habits and life cycles) disappeared into a single, homogeneous commodity stream.
The invention of SYP as a category – and the attendant commodification and standardisation of southern forests – was followed a couple of decades later by the emergence and widespread embrace of tree farms in the US. By the 1930s and 1940s, timber companies were eager to distance their industry from the extractive practices that had cleared the nation’s eastern and southern forests and saw the new tree farm model as a way to flip the script. In the late 1930s, the Weyerhaeuser Timber Company launched the ‘Timber is a Crop’ advertising campaign, framing lumber production as cultivation and careful management, rather than wasteful and short-sighted extraction.
Like food crops, Weyerhaeuser implied, timber crops required expert oversight and regular harvesting to reach maximum productivity. According to this framing, not cutting wood was wasteful, and discouraged the forest from reaching its productive potential – slow growth was waste.
Oils, extracts and chemicals, including creosote, advertised here in 1920, have been employed as treatments, as well as heat, to improve the durability of wood and extend its lifespan
Cultivation paradigms influence the rate and characteristics of individual tree growth, but also condition the wood’s properties in use, as well as its future decay. Managed plantations encourage faster growth that in turn produces wider annual rings and spongier wood, shorter use lifespans and quicker cycling. Some builders speculate that plantation-grown SYP means worse quality, shorter lifespans, and heading quicker to the dumpster.
Just as fast as the loblolly makes lumber for building houses and decks, it is materially and culturally destined to become waste. Loblolly pine’s ‘weediness’ has been profitable and produced an abundance of cheap, accessible wood products. But cheap and plentiful wood products also come with profound costs, from the colonial occupation of native lands and the dispossession of the continent’s Indigenous people, to the eradication of biodiversity in the clear-cutting and monocropping of forests.
People have devised ways to delay wood’s decay for millennia: from charring methods, to incorporating natural oils and extracts, to chemical treatments. Because people in the US believed they had such an abundance of cheap lumber, patented chemical preservation methods took longer to develop there than in Europe. But in the same decades that SYP was coined, and plantation forests became popular in the US, oil-borne preservation compounds like creosote took off as railways – needing massive quantities of durable timber ties for exposed conditions – threaded across the North American landscape.
Wood boards are placed in a vacuum chamber and as air is sucked out, preservatives are injected into the wood tissues. The process makes a functionally different material, imbuing resistant properties that trump even the most decay-resistant species.
‘As with the emergence of plantation forests, the wood preservation industry pitched itself as a means to preserve forests’
As the US Forest Products Laboratory developed wood preservation research and standards and the American Wood Preservers’ Association emerged, a new material was born – one that both shifted the usable lifespan of a given piece of wood, but also removed its ability to decay. As with the emergence of plantation forests, the wood preservation industry pitched itself as a means to preserve forests, arguing that longer-lasting wood would mean less consumption and would also allow a greater range of tree species to be used.
As in the invention of SYP, the paradigm of pressure treating turned multiple species into a homogeneous commodity with similar, standardised cycles of decay. But these optimistic forest preservation arguments didn’t necessarily come to fruition and, as historian Mark Aldrich argues, ‘preservation preserved markets, not forests’.
Chromated copper arsenate (CCA) became the primary wood preservative for residential use from the 1950s until the early 21st century, incorporated into home decks, playgrounds, planter boxes and shade structures. The copper in the CCA is a fungicide, while the arsenic acts as an insecticide, and the chromium fixes the other two elements to the wood.
These chemicals were designed to kill fungi and wood-boring insects but as with all biocides, they also affect ‘non-target organisms’, and those include people. CCA chemicals held tight to wood tissues, but also raised concerns about how they leach into soils and water – entering into the people working with, playing on and living with these materials.
By 2003, the Environmental Protection Agency announced a voluntary ban on CCA-treated lumber. As awareness of health risks increased, the ubiquitous CCA playground structures were taken apart and removed prematurely before their ‘service’ years were over.
Preservatives may result in lumber no longer being considered as wood for the purposes of composting facilities, leading to massive dumps of replaced decking boards and other timber products
Today’s primary wood preservation chemicals, alkaline copper quaternary (ACQ), free from arsenic and chromium, are considered safer and less toxic. But while we might not be concerned about arsenic in the playground, the chemicals persist beyond a ‘serviceable’ lifespan, and they do so by design.
Even after the PT boards are removed, the chemicals persist for decades. Embedded chemicals predetermine the pathways that this wood can take once the deck is dismantled. By the standards of most recycling facilities and landfill, treated wood is no longer technically ‘wood’. In its waste pathway, it becomes unacceptable for most municipal composting operations and instead must be found space in a sanitary landfill. PT sawdust, chips and scraps, which look to the untrained eye like ideal compost material, must be treated as a controlled waste product. Sealed in a landfill with the rest of our monstrous hybrids, the PT board is unintentionally permanent.
So much of the built environment is obsolescent by design, and in a process of continual ‘upgrade’. Garden decking foregrounds this disposition – and in this context brings attention to the tangle of considerations that any material choice must engage.
Terms like renewability and durability signal the potential of both rapid replacement through natural growth, as well as long-term use without degradation. These terms are levied as a pre-emptive defence against potential accusations of wastefulness, but they are themselves imbricated within waste mentalities. PT Southern Yellow Pine is renewable and durable, but only because of a range of interventions into the natural cycles of wood growth and decay.
The timescales of these cycles have been bent to a desire for more, faster and longer-lasting, and yet even as the garden decking is installed, its near-term replacement is imminent.
The fast wood, slow(ed) decay and indefinite chemical persistence of deck boards offer a lens to see how the disposable culture of contemporary building practices are coded into our very materials, the environments from which these materials come and the environments to which they are jettisoned when the time comes for the next upgrade.
If PT lumber evolved to reduce maintenance and delay decay, perhaps – from a late pandemic and climate crisis perspective – it is time to imagine what the reverse could mean: grappling with materials that might be considered toxic or unhealthy, developing a curiosity for material ageing and wasting, and making some time for higher maintenance and care.
Department of Architecture: https://www.ibu.edu.ba/department-of-architecture/