Fire and termites will be no threat to a nine-storey all-timber office block to be built in inner Brisbane, according to the construction team.

Taller wooden buildings exist in Australia and around the world but 25 King, now underway at the $2.9-billion RNA Showgrounds redevelopment site, is touted as the tallest engineered-timber office tower on Earth.

The Brisbane building is due for completion in late 2018.

Cross-laminated timber (CLT) - layers of wood glued together under high pressure with the grain of each perpendicular to the one before and glulum - glued-laminated timber - will be used to erect the 45-metre tall structure.

Once completed 7,900 square metres of office space will be available for lease.

Acting Premier Jackie Trad, who turned the first sod, said it was a breakthrough for a building of its size.

The building is expected to be completed in late 2018. ( Supplied: Lendlease )

"These materials are sustainable, strong and light, with a structural strength akin to the traditional concrete and steel," she said.

Lendlease said CLT had a lower carbon footprint than other building materials, the production process produced zero waste, and timbers were sourced from certified sustainably managed forests.

Lendlease managing director Mark Menhinnit said pre-fabricated engineered-wood was faster to work with and more environmentally friendly.

But what about fire?

"We've done a lot of testing over many years, burnt a lot of wood with CSIRO," Mr Menhinnitt said.

"The building just gets a char on the outside, the structural integrity is maintained through an intense fire event."

And termites?

"Everyone asks that question. It sits on a concrete podium to isolate the timber from the ground so we don't have that problem," Mr Menhinnit said.

25 King will be Lendlease's fifth engineered timber building in Australia.