A piece of scaffolding blew off the the top floors of the trouble-plagued Auckland Council headquarters, smashing the roof and windows of SkyCity Grand hotel.

Strong winds overnight Saturday are believed to be behind the incident at the Albert St buildings in central Auckland which saw a metal plank blown loose and fall dozens of metres below.

Council and WorkSafe are now investigating what went wrong at the old ASB Tower site, which has been plagued with renovation woes.

Cladding repairs were revealed to be $27 million over budget -- up to $31 million from an estimated $4 million when council purchased the building to be its new headquarters in 2012.


Council's corporate finance and property general manager Kevin Ramsay said that "a metal perforated plank, part of the scaffolding system on the upper levels of the building, came away unexpectedly".

"This appears to have been triggered by a very strong gust of wind dislodging a clip on the plank. The scaffolding system has been installed as per the manufacturers specification and an investigation is underway to confirm the root causes.

"The plank did not go through the roof but did cause damage to the surface membrane and ceiling, leading to some water ingress in the corridor beneath."

A SkyCity spokesman said the metal plank damaged two windows and a roof, causing it to leak.

"I can confirm that as a result of a piece of scaffolding falling from Auckland Council's building, there was some damage to two windows and the roof of the SkyCity Grand Hotel.

"This resulted in some minor water damage to the Grand Hotel gym area. Fortunately no one was injured."

Mr Ramsay said the council's contractor and the scaffolding subcontractor were working with SkyCity to repair the damage, which will be covered by the contractor's insurance.

He said the scaffolding system was thoroughly checked and additional safety measures put in place.


A WorkSafe spokesman said the agency was notified of the incident and was still deciding if any action would be taken.