Client for the 13,000m2 new building is Abertawe Bro Mogannwg University Health Board.
The three-storey extension will house renal dialysis, dental and x-ray departments among others, as well as a staff training centre.
The scheme is aiming for a BREEAM Excellent rating, with sustainability features including photovoltaic cells on the roof, use of combined heat and power, and modular services installation.
Completion is scheduled for autumn 2014.
BAM has committed to providing a number of apprenticeships and work experience placements on the project, which is included in the company’s bid for national skills academy status.
BAM is already working on the hospital’s Specialist Rehabilitation Centre.
The scheme was procured via the Welsh Health Estate Designed for Life Framework. BAM has completed more than £300m of projects under the framework, representing around 40% of the awards. Its previous schemes include Ysbyty Ystrad Fawr in Caerphilly and Ysbyty Aneurin Bevan in Ebbw Vale.