Gutter

A device that collects rainwater from the roof and directs it to the ground. A gutter that runs along the eaves to collect water from the roof surface is called a eaves gutter, a gutter that collects water from the eaves gutter and directs it to the ground is called a vertical gutter, and a gutter that connects the eaves gutter and the vertical gutter is called a call gutter or anglerfish gutter. A gutter that is exposed on the outside of a building, such as at the eaves, is called an external gutter, and a gutter that is not visible from the outside, such as on the inside of a flat roof's parapet (a handrail wall found on the roof or in an open corridor), is called an internal gutter. The cross section of a eaves gutter is usually semicircular, and is connected to the vertical gutter with a slope of about 1 in 80 to 1 in 100, but in careful work, the outside of the eaves gutter can be supported by a box-shaped cover, which is called a box gutter. Using a box gutter has the design advantage that the slope of the eaves gutter is absorbed inside the box, allowing the eaves line to be aligned horizontally. The best material for gutters is copper sheet, and usually galvanized steel sheet, although more recently colored steel sheet or formed synthetic resins have also been used. Iron pipes are used for vertical gutters close to the ground where they are likely to be hit by objects, and for particularly long gutters in high-rise buildings. Half-split bamboo is sometimes used for the eaves gutters of Sukiya houses and other buildings. If a valley is formed in the roof, box-shaped gutters are made from copper sheet or similar, but for long land valleys (which are unavoidable with sawtooth roofs), specially formed products that are waterproofed with asphalt are sometimes used. In general, the key to reducing leaks is to avoid internal gutters and to prevent the formation of valleys, especially land valleys.

The eaves gutters are supported by gutter metal fittings attached at regular intervals to the rafters and fascia, while the downspouts are supported by metal grips attached in the same way to the pillars and walls. Both are made of iron and must be treated with anti-rust coatings such as coal tar.

[Yamada Koichi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

屋根から雨水を集めて地面まで導くための装置。軒先に沿わせて屋根面からの水を受けるものを軒樋、軒樋の水を集めて地面まで導くものを竪樋(たてとい)、軒樋と竪樋とを接続するものを呼樋(よびとい)または鮟鱇(あんこう)という。また樋を軒先など建物の外に表すものを外樋、陸(ろく)屋根のパラペットparapet（屋上や吹抜き廊下にみられる手すり壁）の内側などに設けて外から見えないものを内樋とよぶ。軒樋の断面は半円形が普通で、80～100分の1程度の勾配(こうばい)をつけ竪樋につなぐが、ていねいな仕事では軒樋の外側を箱形の覆いで受けることがあり、これを箱樋という。箱樋を用いれば軒樋の勾配は箱の中で吸収されて軒の線を水平にそろえられる意匠上の利点がある。樋の材料は銅板を最上とし、普通は亜鉛めっき鉄板、最近はカラー鉄板や合成樹脂で成形したものも用いられる。竪樋で地表に近く物の当たりやすいところや、高層建築でとくに長いものには鉄パイプが使用される。また数寄屋(すきや)などの軒樋には半割の竹を用いることがある。屋根に谷のできる場合は銅板などで箱形の谷樋をつくるが、長い陸谷（鋸(のこぎり)屋根の場合に避けられない）では、特別にアスファルト防水などを施した成形品を用いることもある。総じて内樋を避け、谷、とくに陸谷をつくらぬようにするのが雨漏りを少なくする要諦(ようてい)である。

　軒樋は垂木(たるき)、鼻隠(はなかくし)に一定間隔に取り付けた樋金物に、竪樋は柱、壁体に同様に取り付けた把(つかみ)金物によって、それぞれ支持される。いずれも鉄製で、コールタール塗りなどによる防錆(ぼうせい)処理を施さねばならない。

［山田幸一］

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