Teen boy dies in fall on Perth work site

The death of a 17-year-old boy who was working at a construction site overnight has been described as tragic and a waste.

The boy fell 12 metres to his death while working at the General Post Office building in the centre of Perth about 4.30am on Thursday.

He is understood to have fallen from scaffolding while installing glass as part of the fitout of the building for Swedish fashion retail giant H&M.

"It is just a tragic event in the first week of the year when the majority of the construction industry is still on their summer break," Construction, Forestry, Mining and Energy Union state secretary Mick Buchan said.

"We are absolutely devastated to wake up to this, what a waste that this young individual will not be going home."

The CMFEU would investigate the death in co-operation with the builder, he said, along with WorkSafe and the coroner.

The work is behind schedule, with the international retailer having missed its mid-November opening target.

WA is the only state or territory where the building industry fatality rate worsened between 2014 and 2015, Mr Buchan said.

German woman Marianka Heumann, 27, died in similar circumstances when she fell down a lift shaft at a Finbar construction site in East Perth less than three months ago.