Construction product makers have upped capacity by 10% over the past two years and expect it to rise by a further 9% over the next two, according to a members’ survey by the Construction Products Association.

The biggest growth areas were insulation, used in energy-saving initiatives, and plasterboard, used in an increasing number of flats.

Of the manufacturers surveyed, nearly two thirds said they were operating at below optimum capacity in the first quarter of 2007, particularly producers of bricks, steel and concrete. Only 12%, including almost a quarter of plasterboard and insulation makers, were above optimum.