The tea house is a small, single-storey, rectangular building with a structural framework of round timbers and lightly squared tree trunks – mainly cedar – and with earth infill panels between the framing. The posts stand on fieldstones. The hipped-and-gabled roof is covered with two different materials: wood shingles to the eaves areas on the south and east sides of the tea room, and reed thatching over the rest of the roof. Internally there are three rooms: the “chashitsu” or tea room; the “mizuya”, where the utensils are washed; and the “katte”, where food is prepared (ill. 2). In its design and workmanship, the tea room, which is laid out with tatami, reveals a high degree of elaboration (ill. 8). This applies in particular to the form of the soffit, the workmanship and the materials used in its construction.
In its architecture, the tea house is reminiscent of simple vernacular farmhouses, but on closer examination one sees that these forms have been sublimated through the application of elaborate craft techniques. The precise jointing of the load-bearing structure, for example, reveals the high degree of craftsmanship that was necessary to overcome irregularities in the round timbers (ills. 3, 4).
Over the years, the structural framework had twisted in a clockwise direction, particularly in the northern half, where there are no bracing walls internally. The feet of the columns and the sills had also been subject to heavy animal attack. Some of the joints between the rails and posts had opened up; and over the rails, the plaster, with a thickness of only 5–6 mm in part, had become loose, with cracks appearing in some places. Heavy damage was particularly evident in areas where earlier restoration work had been carried out.
Tea houses are regarded as venerable structures in Japan, and the value attached to the patina of the rendering over the earth infill panels necessitated their retention, despite their dilapidated state. Before removing any areas of rendering, a facing of Japanese paper was fixed to the surface with methyl-cellulose as a means of securing the material. In order to carry out repairs, individual infill panels were carefully removed where the heaviest damage had occurred and where the distortion to the structural timbers was greatest. The remaining panels were left in place and secured for the duration of the restoration work.
The supporting structure to the earth rendering of the old infill panels consists of a latticework of split bamboo. For the rendering itself, a reddish earth with a high iron-oxide content was used. After a drying period lasting a number of months, shrinkage cracks were filled, the edges of the bays were prepared and an intermediate layer of plaster 3–6 mm thick was applied. The overall thickness of the wall was then about 40 mm. Special care had to be taken around the timber rails, since the rendering is very thin here. To prevent cracking, bundles of flax fibres were pinned on or knotted through holes to the rails.
Where the infill panels were heavily damaged and in those areas where the sills had to be replaced, the rendering was carefully removed and saved for subsequent use. After adding about 30 per cent new clay, the earth plaster was soaked for ten months and rice straw was added. On renewing the rendering over the rails, linen fabric was used as a means of reinforcement. At especially sensitive points, bundles of flax or palm fibres roughly 35 cm long were nailed to the supporting structure. They were not fixed to the load-bearing structure, however, in order to prevent cracking of the rendering in the event of distortion. To avoid shrinkage cracks between the structural timbers and the edges of the bays of rendering, twisted cords of Japanese paper were inserted, with folded strips of paper laid over the top. A narrow strip of earth with a high sand content was then applied. Rice straws were pressed into the surface before it dried and covered with a thin coat of rendering (ill. 6). Special care had to be taken at the junctions between new and existing work. Where the rendering had detached itself from the rails, or the skim coat had separated itself from the base coat, a 15–30 per cent solution of skin glue was injected and the loose areas pressed on for one to three days.
Conservation work in Japan implies more than just the repair of damage. Great importance is also attached to achieving an aesthetically satisfying solution. The repairs to the tea house, for example, were carefully matched in colour to the original. Where the plaster was renewed in larger areas, the surface of the skim coat was treated with a solution of manganese oxide, which was applied with a brush to smaller areas (ill. 7).
A further important part of the restoration work was the renewal of the roof covering. As in many other structures with reed thatching, the intervals between its renewal had grown shorter and shorter. In the case of the tea house, they had decreased from 19 to 13 years in the course of a century. This may be attributed to excessive use of fertilizers and to other environmental factors.
The supporting structure consists of 2 cm bamboo canes tied with straw to the rafters at 20 cm centres (ill. 9). Reeds are first laid out singly and with great care to the eaves to create an attractive visual effect from the underside. The roof covering, in the form of bundles of reeds, is then laid on top and fixed with copper wires. The covering to the roof slopes is 35 cm thick (about 10 cm thicker than European reed thatching). The ridge construction is extremely elaborate (ill. As the most sensitive point of the roof, it has to be especially durable. At the same time, it is also an important ornamental feature and has a symbolic content. The ridge of the tea house was first “packed” by binding bundles of long reeds over the top. Short bundles were then laid transversely to this and covered with two layers of cedar bark. This additional covering, approximately 12 cm thick, was fixed to the supporting structure with bamboo canes and copper wire. Finally, 12 cm diameter bundles of reeds encased in cedar bark were fixed at regular intervals at right angles to the ridge. Originally, this whole construction was tied together with cords. Today, more durable copper wire is used. The subsequent use of palm-fibre cords is merely a visual embellishment. The roof covering is then trimmed with shears, and the eaves are cut (ill. 5).
