Also ni 荷. Lit. load. The downward pressure exerted by the roof structure, purlins, transverse beams, etc. on the lower framework of a wooden building. External pressures from natural causes such as snow, earthquake, wind velocity and the expansion and contraction of materials due to temperature extremes must all be considered to calculate the strength needed for the roof structure. Related terms include: seikajū 靜荷重, a dead load, used when calculating the weight and strength of a beam or an entire roof; jūkajū 重荷重, a very heavy load; idō kajū 移動荷重, a shifting load. The weight of structural members constitutes a still load. External pressures constitute a heavy load. A shifting load is exemplified by Hōryūji *Gojū no tō 法隆寺五重塔, which is constructed around a central pillar *shinbashira 心柱 so that it can sway safely in violent winds or during earthquakes.