The hachiman-zukuri (八幡造) is a traditional Japanese architectural style used at Hachiman shrines in which two parallel structures with gabled roofs are interconnected on the non-gabled side, forming one building which, when seen from the side, gives the impression of two.[1] The front structure is called gaiden (外殿, outer sanctuary), the rear one naiden (内殿, inner sanctuary), and together they form the honden.[2][3] The honden itself is surrounded by a cloister-like covered corridor called kairō' (回廊) (see photo). Access is made possible by a gate called rōmon (楼門).
It has a hirairi or hirairi-zukuri (平入・平入造) structure, that is, the building has its main entrance on the side which runs parallel to the roof's ridge (non gabled-side). There are entrances also at the center of the gabled sides (see image). In general, the rear structure is 3x2 ken,[4] while the front one is 3x1.[1]
The space between the two structures is one ken wide and forms a room called ai-no-ma (相の間).[1] The actual width and height of this room vary with the shrine.
Extant examples are Usa Shrine and Iwashimizu Hachiman-gū. This style, of which only five Edo period examples survive, may be of Buddhist origin, since some Buddhist buildings show the same division. For example, Tōdai-ji's hokke-dō[5] is divided in two sections laid out front and back. Structural details also show a strong relationship with the Heian period style called shinden-zukuri used in aristocratic residences.[1] Another possible origin of this style may have been early palaces, known to have had parallel ridges on the roof.[1]