Culvert Guesthouse

in Nagano

nendo

A storage facility for archiving furniture, products, and artwork in Miyota-machi, Nagano Prefecture, with a guesthouse attached. Located in a quiet and nature-rich environment where streams weave through a thick forest of red pine, the tunnel-like architecture took shape through a combination of precast and prestressed construction methods.

For precast construction, common parts are molded in a factory and assembled on site. An example of its applications in infrastructure projects is the box culvert (box-shaped concrete structures), used to store waterways, pathways, power lines, and communication lines buried underground. However, since the method itself does not provide a leak-free composition nor does it allow for stacking, both necessary for this architecture, prestressing was also used to connect the parts together.The prestressing method is a technique used in civil engineering structures such as bridges, in which the parts are aligned and then tightened with wires to connect them. This results in a seamless and smooth surface finish, obtaining a tight seal, and durability.

The common square-shaped parts weigh approximately 12 tons each, and a total of 63 of these parts were used. The size of the parts was derived from the loading size of the delivery truck and the weight that could be lifted by a crane. The 45-degree reinforcement at the entry corner, which is also found in general box culverts, serves as a brace and enhances earthquake resistance. By connecting these parts, a slender, tunnel-shaped space with an internal dimension of approximately 2 x 2.3 m was created. Fourteen wires were used to connect each “tunnel” and care was taken to apply uniform tension to each wire at all times. The work involved gradually tightening the wires over time until a tension of 46 tons was finally applied to each.

The building is composed of four stacked “tunnels” covered with a roof in the center. In addition to a long, narrow storage room with a depth of approximately 40 meters, there are two smaller storage rooms, but it is envisioned that more will be added to the site in the future as the collection grows. The kitchen, bathroom, toilet, and other water facilities are concentrated on the first floor, and a compact bedroom and a study are located on the second floor.

The windows were made without metal frames as much as possible, and high-transparency glass measuring up to 10 meters in length was fixed into the grooves in the same manner as shoji screens. The gravel and plantings used in the exterior were also arranged in the interior to draw the outside environment into the interior. To make it easier to walk on, the gravel was partially hardened with resin. Instead of just pouring resin over the gravel, which is usually the case, the resin was applied to the base first and then gravel was laid on it so that the surface wouldn’t become glossy. In addition, the door handles would have looked abrupt if installed as-is, so an original handle was designed, which hides in the small gap between the door and the wall. The bathtub is carved into the floor, such that the water surface aligns with the floor, creating the appearance that the tunnel shape is continuous.

The resulting space is less architectural, but rather a project that combines civil engineering concepts with product design details.

日本長野箱涵旅宿

箱涵旅宿（Culvert Guesthouse）座落日本長野縣御代田町一處紅松茂密、小溪流淌的自然森林之中，白色隧道式建築，是涵藏家具、商品、藝術品的保管設施，同時附有一間旅宿，供旅人造訪與歇息。

具有建築設計背景的佐藤大（Oki Sato）再度發揮鬼才創意，運用預鑄箱型涵洞（箱形混凝土結構），結合預力樑工法，打造出一座箱涵建築。整體結構由四個箱涵隧道，以井字型堆疊而成，中間覆蓋屋頂，每個箱涵隧道大小不一，最長可達40公尺，室內則是2 x 2.3公尺的細長形隧道空間。由於建築主要用途為儲藏物品，40公尺隧道是此處最狹長的儲藏室，另外還有兩處儲藏空間，廚房、衛浴、衛生間等用水設施，全數設置於一樓。橫貫在二樓的箱涵隧道便為旅宿，設有臥室和書房。

箱涵隧道是由事先在工廠預鑄的方形涵洞，以製作橋樑的預力樑工法，對齊、綑綁而成。總共使用了63個方形涵洞，每個涵洞重約12公噸，每個隧道各都運用14條金屬鐵絲連接著，完整對齊後，必須不斷收緊鐵絲，直到每根鐵絲都施加46噸的張力，才完成無縫光滑的表面，達到穩固的密封性和耐用度。獨特的建築結構意味著許多挑戰。井字型堆疊的箱涵隧道之間，存在著空隙，nendo將此些空隙變成建築窗景，並盡可能不使用金屬窗框，利用日本傳統和室常見的襖(ふすま)和障子（しょうじ）橫拉門，轉化為長達10公尺的高透明玻璃，輕透無限的窗景若有似無，迎入周遭盈滿綠意茂盛的松葉林。

箱涵隧道的兩端開口，同樣是玻璃窗景，睡覺的時候看著窗外星空，望向窗外的浴缸也採用降板設計，使水面與戶外地板齊高，呈現更為流暢延伸的隧道延伸感。白色屋頂下的中心場域，將礫石與植物從戶外延續到室內，為便於行走，室內地板先鋪上一層樹脂，接著鋪上礫石，等樹脂硬化發揮黏著度，行走時石頭就不會隨著步伐而移動。「由此產生的空間不是建築，而是一個將土木工程概念與產品設計細節相互結合的設計作品」－nendo

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www.nendo.jp