Plants used in the thatch prototype. from far left: European Water Reed (Phragmites Australis ) Winter Wheat (Triticum aestivum ) Switchgrass (Panicum virgatum ) Prairie Cordgrass (Sporobolus michauxianus ) Big Bluestem (Andropogon gerardi ) Little Bluestem (Schizachyrium scoparium )
So, I asked, what would thatch look like in the contemporary Outouais region, both as place-specific, multi-species cladding and as a technical reality within today’s building industry? Doubtlessly, this hypothetical condition requires magical thinking – near future, sci-fi speculation involving a drastic shift in the government’s relationship to their own stated climate goals. But it also begs for tangible testing and physical prototyping, as speculation will never accurately predict the tactile and dynamic lessons inherent to an act of making. I began by sourcing and foraging for six species of plant spanning three broad categories: agricultural, invasive and native; each category bearing a unique set of infrastructural implications. The first species is winter wheat straw, a byproduct of agricultural grain production. As such it represents the candidate which – in its present state of industrialised commodification– is nearest to a state of fullscale supply chain integration, that could ostensibly meet the demands of housing contractors. Winter wheat is specifically important to Ontario’s agricultural economy because it is used as a cover crop between corn and soy rotations, offering a soil-replenishing alternative to fallows. Incidentally, Letts describes winter wheat as one of the most resilient thatching species used in England prior to the mid- twentieth century. The second species is European Water Reed (Phragmites Australis australis ), an invasive cousin of the Phragmites Australis americanu s, which is native to Central and Eastern North America. This plant grows in dense thickets at phenomenal speeds while releasing toxins from their roots, effectively outcompeting most native wetland species in their natural habitats. The Canadian government has officially sanctioned its elimination, wherever possible, though this process is arduous and the success rate is low. Incredibly, this very species is the most common thatching material in Denmark, and is often cited as the most durable thatch, with a 50+ year expected lifespan. It may thus be useful to speculate on the compatibility between the prescribed management of Phragmites and its usefulness in construction.
The remaining species consist entirely of perennial grasses native to Ontario: Big Bluestem ( Andropogon gerardi ), Little Bluestem ( Schizachyrium scoparium ), Prairie Cordgrass ( Spartina pectinata ) and Switchgrass ( Panicum virgatum ). 97% of Ontario’s native tallgrass prairie ecologies have been depleting due to urbanisation and agricultural expansion. The Tallgrass Prairie initiative was introduced to raise awareness about this vanishing landscape and to persuade farmers to plant tallgrass species on agricultural land. Unintuitively, perhaps, this includes routine thinning and mowing, which lends us the opportunity to speculate on the use of their excess as thatching material. Though these four species are not discussed in thatching literature, they satisfy Hall’s description of a thatch candidate and are thereby worthy of further material investigation. All three of these thatch categories, agricultural, invasive and native, present opportunities for farmers to add value to their crops while catalysing new biogenic building practices. But these new, hyper-local supply chains require additional infrastructure which do not presently exist in so-called Canada. For instance, modern combines chop straw far shorter than the minimum required length for thatch, and there are no industrial instruments which specialise in the harvest and threshing of reed or for parsing out wild grasses. Beyond this, there are the concerns about building code inertia mirrored by an understandable reticence of industry professionals to integrate vernacular crafts into a well-worn construction regime. While the former concerns must be left, for the moment, to the realm of science fiction, I address the latter through design (speculation in another skin). I went on to detail a prefabricated, unitised thatch cladding system which is pressed into forms under controlled conditions in specialised facilities, after which it is shipped off to building sites and installed. The unit consists of two parts: a recyclable wedge which is affixed to the structure, and the thatch overlay which is strapped down to the wedge, suspending the fibres away from the envelope surface at an angle of 20°. The bands which secure the stems to the wedge are spring-loaded so that
42 on site review 48 :: building materials
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