An Australian man, clad only in underwear, fell nine stories while trying to build a makeshift plank bridge into a neighbor's flat, but lived to tell the tale.

The bridge collapsed just after midnight Tuesday sending the 35-year-old man plummeting into a building structure below, police in Western Australia state said.

"He was skylarking around, building planks across to his neighbor's place when it happened. He was very lucky. It was an iron and timber structure, possibly a pergola, that cushioned his fall," police spokeswoman Ros Weatherall said.

The man was recovering in hospital with cuts and a suspected broken leg.