Boral is looking to buy US-based building products manufacturer Headwaters for about A$3.5 billion.

Boral announced the acquisition this week, and while it is still subject to Headwaters shareholder approval and regulatory approval, the company says it could be completed by mid-2017.

“The businesses of Headwaters are highly complementary with Boral's existing US operations - in fly ash, roofing, stone and light building products,” Boral CEO and managing director Mike Kane, said in a statement to the ASX.

“It's this strong alignment that means we can deliver substantial value through synergies - ramping up approximately $US100 million per annum of synergies within four years of closing.”

The deal values Headwaters at $US24.25 per share, a fair premium on recent closing prices of around $US20.10.

The takeover is set to be funded by the issuance of over $2 billion in shares, as well existing cash and by taking on debt.

Boral is hoping the election of Donald Trump to the US presidency will see increased infrastructure spending, allowing the company to supply more of the materials that will be needed for such construction.

“While this acquisition is significant in scale, we have maintained a disciplined approach to reviewing growth opportunities in the USA,” said Boral chairman Brian Clark.

“Headwaters has been rigorously assessed and with its highly complementary portfolio of assets, which are strategically aligned with a number of Boral's existing US businesses, this is a highly compelling acquisition for Boral.”

Boral's equity raising will run at $4.80 per share - a 22 per cent discount to its close of $6.15 before the announcement.