Marley recommended that shareholders accept the 125p-a-share offer, which represents a 60 per cent premium to its share price a week ago, as Etex went into the market to buy a 20 per cent stake in the company.
David Trapnell, chief executive of Marley, yesterday insisted Etex had approached Marley about the deal "weeks before" the hostile bid last week from John Mansfield, the small timber merchant being used as a takeover vehicle.
"We have known this group [Etex] for a long time and there has been a close link over the years. We have been talking and in the last few weeks we have taken that talk a stage forward," Mr Trapnell said.
Mr Trapnell said Etex had assured him it would keep the group intact "for the time being".
Mr Trapnell and Chris Beenham, the finance director and the only other executive director, will leave after staying "a few months" to oversee the integration with Etex.
Etex is a privately-owned building materials group, roughly twice the size of Marley, with a turnover of 74.8 Belgian francs (pounds 1.4bn).
Specialising in plastics, roofing and flooring, it has operations in Europe and Latin America, including a joint venture with Marley in Brazil.
Its offer came just six days after the hostile paper bid by John Mansfield Group, a takeover vehicle headed by Stuart Wallis, the former chairman of Fisons, and backed by the financiers Brian Myerson and Julian Treger.
John Mansfield said yesterday it was "considering its options". But sources familiar with the company said it was unlikely to make a higher bid.
Phillips & Drew fund management, which holds a 14.9 per cent stake in Marley, encouraged the break-up bid after meeting Mr Trapnell in September to discuss the company's strategic review.
The fund manager was said to be "very disappointed" when Marley came out with no firm plan of action after years of poor performance.
It agreed to underwrite pounds 1.5m of John Mansfield's costs and is now sitting on a profit of around pounds 20m as a result of the takeover battle.
The Etex offer caused Marley's share price to jump 17.5p yesterday to 123p, up from 78p last week.