富良野の異形屋根
The Deformed Roof House of Furano 2018
















富良野の異形屋根〜北海道民家のマニエリスム
1974年に建てられ、2度の増改築を経て現在の形となった住宅を二世帯にリノベーションする計画である。異形屋根と称するこのような住宅は、北海道では馴染み深いが美しいとも言い難く、道外では見たことがない。ともすればバナキュラーでアノニマスなデザインであるようにも思えた。
北海道近代民家史を簡単に振り返ると1950−60年代に三角屋根(※1)の様式が確立し、後を受けた異形屋根(※2)の時代は60年代から10年ほど続いた。異形屋根様式は様々な視点から分類可能であるが、様式変化の理由について調べると肝心の動機がわからない。
もっと俯瞰して人類史の視座で考えると、ルネサンスのような「自⽴した様式の概念」ではなく、「正当な様式からのズレとして定義される人類が歴史的に繰り返す概念」であるマニエリスムとすると整理がつく。近代でいうモダンとポストモダンの関係のように、三角屋根に対する異形屋根と位置づけることは、それほど乱暴な話ではないだろう。そのような北海道民家史における奇想とも言える異形屋根住宅を次の世代に繋いでいくことが計画のベースとなった。
改修は1階を親世帯、2階を子世帯とし、必要所室を満足させるためには増築の必要があった。また断熱改修と構造補強も要請されていたためスケルトンまで解体し、異形屋根形態をトレースして妻側に約1間建て増した。増築部分は親子世帯を緩やかに繋げると共に農業ハウス的な空間性質を持つ共有部として、テラス、風除室、アクセス空間などの機能を兼ね備える。農家に不可欠な土間でもあり、職と住を横断する空間ともなっている。そして半屋外空間とすることで増築コストを抑えた。増築部の構造は105×180@1820で柱が立ち、耐風圧を柱の長手方向で受けることで横架材をなくす。決定された構造デザインに(ある意味強引に)プランを重ね合わせることでテラスや開口にズレが生じ、アップグレードされたマニエリスティクな様相が建ち現れた。
※1三角屋根
コンクリートブロック構造でリビングが中心にあり廊下のない平面、屋根は木造で矩勾配の板金仕上げで雪を落としやすくしているのが特徴で、その背景には1953年に制定された「北海道防寒住宅建設等促進法(寒住法)」がある。法に従うことで同形状となった住宅は、敷地中央に配置され、均質に区画された分譲宅地に美しくリズミカルな街並みを形成した。
※2異形屋根
異形屋根の形状には幾つかのパターンがあり、屋根は板金で葺かれている。三角屋根から様式変化した背景には、寒住法の融資範囲が木造住宅へ広がり設計が自由になったこと、板金技術の向上で複雑な屋根形状を作ることが可能になったことがあるが、このデザインの推進力が三角屋根様式の技術改善であることを明確に見いだすことはできない。
※1三角屋根の事例


※2異形屋根の事例





用途 専用住宅 所在地 北海道富良野市 敷地面積 m2 建築面積 96.42m2 延床面積 203.28m2 設計 髙木貴間建築設計事務所 髙木貴間 構造 長谷川大輔構造計画 長谷川大輔 写真 佐々木育弥
The Deformed Roof House of Furano ~The Mannerism of “Minka (local houses)” in Hokkaido~
This plan is to renovate a house, built in 1974, into a two-family house. Its’ current figure is a result of going through extensions and reconstructions twice. Housings such as these which are called “Deformed Roof” houses, can be seen often in Hokkaido, but is difficult to call them beautiful, and cannot be seen out of Hokkaido. It could be said as a vernacular and anonymous kind of design.
Looking back on the modern history of “Minka” in Hokkaido, the style of “Triangular Roof” houses (※1) was established in the period of 1950’s~1960’s. The period of “Deformed Roof” (※2) houses followed that, and lasted for about 10years after the 1960’s. When researching about the reasons of the style change, it is possible to assume by circumstantial evidence, but cannot reach the most important point, which is the motive.
Considering from a different point of view, such as human history, it can be outlined by saying that it is mannerism, which is defined as a divergence from the legitimate style, and a concept that humans repeat historically, rather than a “concept of an independent style”, such as Renaissance style. Like the relationship between modern and post-modern in history, to place “Deformed Roof” houses towards “Triangular Roof” houses would not be so inexplicable. The base of this plan was to pass this “Deformed Roof” house, which can be said as a conceit in Hokkaido “Minka” history, down to the next generation.
The house was renovated so that the parent household would be on the 1st floor and the child household on the 2nd floor, and also extension was done to fulfill the necessary rooms. Since insulation improvement and structural reinforcement was also required, the house was disassembled to its’ frames, and was extended for 1 “ken (a Japanese unit, 1 ken=1,820mm)” on the gable end, tracing the form of the deformed roof. The extended part softly connects the parent household and child household, and also functions as a share unit with an agricultural greenhouse-like nature, possessing features of a terrace, windbreak room, and an all access area. It is also a “doma (dirt floor)”, which is essential for farmer households in Japan, and is also a cross-section space for work and living. Extension cost was reduced by making it a half-outdoor space. In the structure of the extended part, a pillar is placed by 105×180@1820, and by receiving the wind pressure resistance by the longitudinal pillar, the horizontal member was excluded. By layering the plan (rather forcefully) to the decided construction design, a misalignment arose in the terrace and opening, which led to the appearance of an upgraded manneristic dimension.
※1 “ Triangular Roof” houses
The features are 1) concrete block constructed, 2) the living room placed at the center, no corridors in the floor plan, 3) the roof built by wood by gradient method and sheet-metal finished, in order to make it easier for the snow to fall off. The background for such features is that in order to get financial aids, the house had to be built following the “Hokkaido Cold-Proof Housing Construction Acceleration Ordinance (established 1953) . By following the ordinance, houses were placed at the center of building sites, creating beautiful streets with a kind of rhythm in the homogenously divided residential lots.
※2 “ Deformed Roof” houses
There are several patterns in the shapes of “Deformed Roofs”, and all are roofed by sheet-metal. One of the reasons of modal alteration from “Triangular Roofs” is that the range of financing was expanded to wooden houses, allowing more freedom to the design. Another is the advancement of sheet-metal technology, which made it possible to build roofs in a more complex figuration. Nonetheless, it cannot be expressly said that that the driving force of this design is the technical improvement of “Triangular Roof” style.