Weekend House Osaka

Hiroshi Nakao

Subject | The architect Hiroshi Nakao, only 35 years old, has also made a name for himself as an artist through various exhibitions in Japan and elsewhere. Professor Masao Furuyama from the Technical Institute in Kyoto describes him as not belonging to any architectural or artistic school, his architecture representing an antithesis to conventional visual refinement and his work resisting all explanation. He refers to him as an architectural archaeologist who digs deep, discovers his works like archaeological treasures and then reveals them to the world. So, like stone-age artifacts, his works are uncannily corporeal, yet inexplicable. According to Furuyama, Nakao's architecture is like coal - originally wood but now highly compressed and mutated into jet-black stone.

His "Dark Box and Birdcage" (Nakao's title for the weekend house), built in 1991, is a petrified black object like a mineral, like a crystal. Of course, this interpretation is very sympathetic to the pure geometrical styling of classical Japanese architecture. Perhaps this approach even evolved from this almost abstract type of architecture. In any case, the weekend house is an extraordinarily simple and clearly defined structure which, with its sparse furnishings, exudes a Zen-Buddhist composure. Simple means have been employed here to create a room layout which is up-to-date but also timeless.


Prefecture Osaka, Japan (further details withheld at the request of the client).


Nakao Serizawa Architects, Tokyo

Design Team

Hiroshi Nakao, Masahiko

Inoue, Hiroko Serizawa

Structural Engineer Mase Building Agency

General Contractor Tomi Komuten

Date of Completion 1991


The project cost 25 million Yen.

Design | Hiroshi Nakao has accommodated the simple layout in a basilica-like structure based on a 3 x 3 m grid. The tall "nave" contains the living room and the equally high internal courtyard, linked with each other via a large glazed wall. The upper section of the courtyard walls above the "lateral aisles" is broken up by horizontal slats. Like in a clerestory, the light penetrates into the courtyard through these slats and also from above via the open roof. At the rear of the living room there is a small gallery (approx. 6 m2) which can only be reached by a ladder. The ladder is located in an imaginary vertical "shaft" identified by three circular openings: a rooflight at the top, the access opening at gallery level and a recess in the living room floor which is filled with black pebbles. These define the position of the ladder and crunch when ascending or descending - a sensory effect desired by the architect.

6 | Section, scale 1:25. Roof construction from top to bottom: roofing felt, 8 mm asbestos-cement sheeting, 4 mm plywood, 60 x 120 mm members laid to match roof fall on 105 x 180 mm roof joists, 50 mm thermal insulation between 60 x 120 mm members, suspended timber lattice comprising 38 x 45 mm battens, 4 mm plywood ceiling.

External wall contruction from outside to inside: horizontal 240-mm-wide tongue-and-groove planks, waterproof sheathing paper, 9 mm chipboard, 40 x 120 mm studding at 500 mm centres, 50 mm thermal insulation in the bays; in living areas, tongue-and-groove planks as on the outside, otherwise 4 mm plywood on 15 x 45 mm battens.

Floor: surface of 36 x 200 mm planks on 40 x 45 mm battens, mortar levelling course, concrete ground floor slab, polyethylene sheeting.

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7 I Horizontal section through exterior wall, scale i:io. Left, an exterior corner; right, joint with patio door between study and internal courtyard.

The living room extends on both sides into the lower lateral aisles where the floor too is 150 mm lower. This leads to an unusual dual usage: on the side facing the road the aisles are provided with sliding doors so that they may be used as garages if required. The aisles extend alongside the internal courtyard, providing - on a 450 mm plinth - kitchen facilities, bathroom and a small bedroom on one side as well as entrance hall and study on the other. Both the bedroom and the study open across their full width onto the middle courtyard. Furthermore, the study also opens across its full width on the other side onto another small, enclosed and lower courtyard situated at the end of the carport and access area. Hence the result is highly differentiated spaces with different lighting effects. However, the underlying harmony of the black-painted, strict geometric wooden surfaces prevails; floors, walls and ceilings which in no way conceal their identity.

Structure | The structure, exclusively of timber-frame, is erected on a concrete substructure and reinforced concrete foundations. The 120 x 120 mm timber columns of the main framework are arranged in a 3 x 3 m grid on continuous 105 x 105 mm or 105 x 150 mm sole plates supported on the concrete strip footings. Only at the road end is the final bay shortened to 2.3 m. In the middle rows of columns, between "nave" and "lateral aisles", the columns are connected together by 105 x 240 mm beams at the level of the aisle roofs and by 105 x 180 mm beams at the level of the nave roof. Fixed to these are the loadbearing 105 x 180 mm roof joists which are positioned at half the bay width, i.e. at 1.50 m centres. The lower outer walls of the aisles are of identical construction and form the exterior supports for the roof joists. The roof joists in turn carry 60 x 120 mm secondary members at 400 mm centres which support the actual roof construction and are positioned at different levels to accommodate the 1 in 20 roof fall.

The external walls incorporate 120 x 40 mm studs at 500 mm centres between the main columns. Attached to the inside of these are 240-mm-wide tongue-and-groove planks which are butted together at the main columns and which are provided with vertical 34 x 36 mm cover strips at all studs and main columns. This surface made up of horizontal planks and vertical battens at 500 mm centres prevails over the entire building. Only in some ground-floor areas is the interior cladding in the form of smooth plywood panels. On the outside face, 9 mm chipboard, to brace the whole construction, is screwed to the intermediate studs and main columns. This is followed by a waterproof sheathing paper and tongue-and-groove planks like the inside. The 50-mm-thick thermal insulation is placed between the vertical studs.

The 60 x 120 mm members supporting the roof construction are covered by one layer of 4 mm plywood and one layer of 8 mm asbestos-cement sheeting followed by the actual roofing felt. The thermal insulation - again 50 mm thick -is nailed onto the underside of the plywood. The roof beams support a suspended ceiling consisting of 4 mm plywood on a grid of 38 x 45 mm battens suspended on 30 x 36 mm hangers.

The floor is made from 36 x 200 mm planks which are fixed to 40 x 45 mm battens at 400 mm centres. These are supported by 105 x 105 mm members or, in the areas where the floor is lower, embedded as fixing strips in a mortar levelling course which covers the entire concrete ground floor slab. Polyethylene sheeting is laid on the compacted ground under the concrete to protect against rising moisture.

All wooden surfaces, including cover strips as well as window and door frames, are painted black. This ensures the lighting effects which the architect wished to achieve - the contrast between jet-black and glistening brightness.

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