Mining services contractor Decmil has won a $28 million contract to build accommodation for Fortescue Metals Group in the Pilbara.

Decmil will build a 200-person rail camp south of Port Hedland as part of FMG's T155 rail expansion program.

Construction will begin next month with completion expected in the second quarter of the calendar year.

The rail camp contract involves the delivery of 200 single person accommodation rooms (with an option to increase to 514 rooms), a wet mess, gym and recreational facilities and administration and central facilities.