(Adds detail, Seven Group ownership, background) July 30...

(Adds detail, Seven Group ownership, background)

July 30 (Reuters) - Australia's Boral Ltd (BLD) said on Friday it appointed diversified investor Seven Group Holdings (SVW) boss Ryan Stokes as its chairman, marking a new twist in the months-long takeover battle for the building materials supplier.

Seven Group, which now owns nearly 70% of Boral, has been steadily increasing its stake in Boral over the past 15 months at a time when the Australian real estate market is strengthening and property prices are surging.

Earlier, Seven Group made a A$8.75 billion ($6.48 billion) bid to take full control of Boral, but was rejected by the building materials supplier saying it undervalued the company.

Seven Group on Thursday https://cdn-api.markitdigital.com/apiman-gateway/ASX/asx-research/1.0/file/2924-02401391-2A1312716?access_token=83ff96335c2d45a094df02a206a39ff4 lifted its stake in Boral to 69.6% from nearly 20% in September last year.

Boral also announced on Friday the retirement of Chairperson Kathryn Fagg, and the appointment of Richard Richards, a Seven Group nominee, as a board director.

($1 = 1.3514 Australian dollars)