Ardian beat off bidders such as 3i, Triton, Pamplona and Lone Star, people familiar with the matter said.

Cinven did not disclose financial details but two people close to the deal said Ardian's offer valued SLV at around 800 million euros (716.89 million pounds) including debt.

The buyout will be backed with an all senior loan financing of about 360 million euros or 5.5 times SLV's expected core earnings, according to bankers.

SLV is expected to post earnings before interest, taxes, depreciation and amortisation of about 65 million euros this year.

Ardian declined to comment.

Cinven bought SLV for around 550 million euros in 2011 and made three bolt-on acquisitions. At the same time it expanded SLV's markets outside Germany into neighbouring countries.

Ardian may further expand into markets including the United States and Britain, a person familiar with the matter said.

SLV is benefiting from strong construction activity in Germany and other countries and from regulations pushing energy-efficient technologies like LED lamps.

The group was set up in 1979. Since being acquired by Cinven, it has invested in logistics sites and bought Swiss LED lighting fixtures maker Unex.

(Editing by Jon Boyle and Susan Thomas)

By Arno Schuetze and Claire Ruckin