Before settlements appeared, some of the earliest shelters were made by nomadic man who would have fashioned sticks and canvas (animal hide skin) into structures. Similar shelters are still in use today. The tupic, a tent dwelling, is built in lieu of an igloo during the summer months by the Inuit people of the Arctic. ‘Constructed from slender poles made of pieces of antler or willow wands lashed together’(29), the tent protects the Inuits from the worst of the weather.
At the other climatic extreme are the black tents of the Tibetan nomads. These are designed to protect against radiant heat with the thick, dark woven cloth providing shade from the sun. Oliver reports that in essence ‘the tent cloth is a membrane held in tension with guy ropes and stretched over, or between, a number of poles.(30)
Both of these structures are designed to protect the occupant from the worst of the severe climates while also being light enough to pack up and move on to the next location. The materials need to be locally available and very efficient at performing their given role. Any wastage is translated into extra weight which is unwelcome when you spend your life on the move.
Hemp stalk is extremely efficient in its structure, its relative strength made even more impressive by its light weight. It could effectively perform as a transportable material. However an individual stalk lacks the robustness that the nomadic peoples would traditionally choose to ensure the longevity of the materials. It is too easy to bend a hemp stalk, rendering it useless.
The black tents use as few elements as possible to take the total load of the cloth. For hemp to take the same load, a greater number of stalks would be needed and would therefore be less practical. Also using long sections of the hemp stalk would increase the likelihood of bending and buckling. Instead the hemp needs to be regularly supported along its length to reduce the risk of such failures.
The Ituri pygmy shelter or lobembe consists of a ‘light domical hut of thin saplings, stripped of their bark and bent to define arcs. [...] A net of thin, peeled withies is then woven into a skeletal frame until the dome is complete’.(31) This is subsequently covered in large waxy leaves creating a waterproof shelter inside.
Replicating such a technique with hemp highlights its tendency to buckle. The saplings used for the lobembe are much more supple and able to weave in and out of one another. This creates a tension within the woven material which is reduced if the individual elements buckle. A technique where the hemp stalk’s structural integrity is retained may be more appropriate.
The Marsh Arabs of southern Iraq use reed to construct their dwellings. A number of weak elements are clustered together and tied to form one larger and stronger element.
Because of their attenuated form and length-to-width ratio, grasses alone are not suitable as structural materials. They have great flexibility and elasticity, but little compression strength and, when severed from their roots, insufficient rigidity to support their own weight. Bundled and tied, however, certain grasses can be used structurally.(32)
This approach may be beneficial for hemp stalk as well. Bundling and tying many stalks together would provide lateral support for each stalk, reducing the risk of buckling and increasing the overall stiffness of the element. By staggering the stalks along their length it would be possible to exceed the length of an individual stalk, producing elements of any required length.
The Tuareg people in the southern Sahara combine large bundled elements with external matting which both stiffens the frame and provides a cladding. A mat is usually ‘formed from different varieties of palm and rattan and is widely used in the construction of buildings and shelters throughout the world, principally in walls, but also in roofs.’(33)
Bamboo is often split, flattened and woven into mats.(34) It ‘can be cut this way because of its structural properties and long fibres with their parallel orientation’.(35) By splitting the hemp stalk in a similar manner it becomes more pliable and weaves around larger elements with greater ease. Hemp fibre could also be used to tie or weave, either as a processed product or in its natural stripped state.
Varying success is achieved by the different weaving techniques. Some produce a flexible fabric while others are stiff in one or two dimensions and could be used as supporting elements.
An alternative to weaving or bundling is to create joints between the individual elements. This relies less on the mass of material and more on skilled workmanship, joinery and an understanding of loading physics. Elements can be built into extremely efficient structures, such as space-frames, where the material is only placed along the lines of loading forces. The Institute for Lightweight Structures, University of Stuttgart, has undertaken advanced research into the use of stick materials (specifically bamboo) in such structures as space-frames.
Hemp is lightweight and efficient in its load bearing capacities and could therefore work in similar space-frame configurations. The connections between the structure’s members are put under a lot of stress, therefore the joints need to be extremely strong. ‘The stability of bamboo constructions depends on the strength of the material, on the correct tight knots and the rope used for lashing.’(36)
Plemenka Supic describes lashing as the ‘oldest, universal method used to assemble different materials.’(37) It creates a strong connection between two elements however can loosen when the joint is worked and can also allow the materials to slip down each other’s length. A strong lashing joint may also apply pressure on the elements. Hemp has a hollow centre which could be crushed if the lashing were too tight. A pin-joint restricts movement of the two elements relative to one another. They may also need to be tied to stop either element slipping off the pin. However, this joint involves creating a hole through the stalk which could compromise its structural strength. These jointing techniques are explored with hemp as photographed below.
From this analysis it is possible to see that hemp has many potential applications as a structural frame. Perhaps its most efficient use would be within a space-frame structure. The examples discussed above could prove interesting as a possible reaction to Third World shelter demand. However, they are unlikely to be utilized in a developed country where housing standards and building regulations have to be met. A more complete building envelope, separating interior and exterior, cannot be provided solely by sticks or stalks. It is therefore important to find materials that work in symbiosis with hemp, creating a total solution.