Celotex turned over £70m last year supplying rigid insulation boards designed to raise the energy efficiency of buildings.
The East Anglian business was established 30 years ago and employs a 170 strong workforce at two production lines based in Hadleigh near Ipswich.
Recently it extended capacity with a new £3m distribution and innovation centre in order to support its growth on the construction markets.
Saint-Gobain, which already supplies the insulation market with its Isover brand said the acquisition, which is subject to Office of Fair Trading approval, will enhances its insulation offer for new segments such as flat roofs and floors.
It also strengthens its positions in the insulation for the new construction and renovation markets.
Celotex will continue to operate under its brand name and with its existing management team.
