Bunnings will invest more than $100 million in the developments, fit-outs and stock for the two stores.

The projects will create more than 380 permanent jobs and more than 760 jobs during construction.

ADCO Constructions are the appointed builders for construction on both sites and are busy with the store builds.

Bunnings chief operating officer Peter Davis, at Castle Hill, said the slabs for the two car park levels have been completed, structural steel has been erected and the concrete panel walls are being put into place, construction of the roof has begun and floor slabs for retail space will soon be laid.

At Rouse Hill, the erection of structural steel framework has begun and the first slabs have been poured for both the retail level and the undercroft car park.

"Bunnings is committed to working toward carbon neutral growth and long-term footprint reduction and, in keeping with this, the proposed Bunnings store will implement a number of energy and water saving design features," Mr Davis said.

Both stores are expected to open for trading in mid-2012.