Perth-based mining contractor Macmahon expects to make just $2 million from the sale of its construction business.

Macmahon said it was selling its construction assets to Leighton Contractors for $20 million but only expects to make $14 million transferring employee liabilities.

It also anticipates it will incur restructuring and redundancy costs of about $12 million, reducing its total profit to $2 million.

Macmahon said its decision to sell out of construction was part of a new strategy to become a dedicated mining services contractor.

Under the deal, most of its construction projects will be transferred to Leighton, apart from four, which are nearing completion.

The company said some people would lose their jobs but had not put a figure on it yet.