In this modern building industry, local, organic materials – such as the grasses and reeds that may once have been stitched onto the purlins of farmhouses along the Saint-Lawrence River – do not comfortably fit the code specifications set by these synthetic and economically optimised precedents. Organic materials are as they’ve always been: regionally diverse, seasonally idiosyncratic, qualitatively malleable; in short – alive. The exception is wood - which occupies exaustive sections of our Part 9 code. Settlers tended to favour wood cladding such as bark, shakes and shingles over yealms (thatch bundles) of grass as they built permanent shelters, which is why the log cabin belongs to the Canadian vernacular imagination, and thatched cottages belong to England – a country whose forests were exhausted by the twelfth century. Thatching was simply slower and more laborious than installing shakes, and straw had added value as fodder while wood was free and endlessly abundant. Nonetheless, many material scientists, forestry experts and biogenic building collectives are reluctant to embrace lumber as a catch-all solution for climate-conscious architecture. The International Code Council only grades a limited number of species for use in the built environment. These are typically planted in expansive monocrop stands; artificial landscapes which are tragically vulnerable to pests, disease and fire. When these stands ignite they take enormous swathes of forest with them, irrespective of conservation status, and send megatons of greenhouse gases into the atmosphere, worsening the effects of climate change which, in turn, exacerbates blaze conditions. Our reliance on wood should be limited as we innovate in the field of climate conscious architecture, especially for non-structural elements.
Silviculturalists plant these fast-growing, uniform forests for the same reason farmers pump fields of homogeneous, calorie-dense crops with synthetic fertiliser and fungicides: to maximise yield and minimise input cost. This commitment to productivism over ecological health is baked into the function of ‘Canada’ as a settler colonial project. So-called Canada is a political condition superimposed over a geographic region, wherein colonial heads-of-state have sanctioned the exploitation of natural resources and the expropriation of land for the ultimate end of capitalist wealth accumulation. ‘Canadian’ designers working towards regenerative architecture will not successfully decouple our building material culture from climate violence without a paradigm shift in this underlying economic pretext. This means reducing our reliance on global supply chains and productivist economies of scale, while turning instead to local supply systems at the scale of the bioregion. This may look like our material pallets shifting regionally, based on local viability of minimally processed, ecologically benign materials. Thatch, as an unregulated vernacular building technique, is relatively non-discriminating in terms of species requirements, which historically has allowed for striking regional variation. Though I have found no survey of thatching typologies used on Turtle Island, John Letts has observed hundreds of species of reeds, wild grasses, cereals, bracken and rushes on English roofs while Nicolas Hall describes potential thatching candidates as any plant with a long, woody, hollow stem. 1 When these shoots are combed of leaves and laid out in parallel on an adequately steep slope (a recommended minimum of 45°), water will run down and off their cut ends rather than pooling. Generally, liquid moisture will not penetrate to a depth beyond the first 10 cm. Thatch can provide additional insulation of up to R-2.0 per inch, depending on the thatcher’s skill at achieving even and optimal compaction. It is also important to recognise that thatch degrades over time. Straw, for example, will decompose at a rate of about two centimetres per year due to prolonged exposure to precipitation. These decomposing ends can look grey and haggard or become green and alive with moss. Traditionally, English thatchers would add a new layer of thatch to their roofs once the end of the crooks (the hooks which tie the thatch to the roof) could be seen. Over the years this would result in thick, multilayered roofs, with thatching materials telling the story of what materials were locally available throughout the lifespan of a building.
section through a traditional thatched roof, from the ouside through to the rafters: thatch yealms laid in parallel wooden sways holding dow thatch at mid-length straw rope fixing sways to battens, Iron crooks or hazel spars also used in traditional thatch battens rafters
Nicolas Hall, Thatching: A Handbook.
1 Letts, John, and James Moir. Thatching in England 1790-1940. vol. 5 . Swindon UK: English Heritage Research Transactions, 1999. pp 58–67 2 Halls, Nicolas. Thatching: A Handbook . Rugby UK: Intermediate Technologies Publications, 1988. pp 3–4
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on site review 48 :: building materials
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