The chief executive of building products group CSR says she is keeping a tight rein on costs in an uncertain market where revenue in the core business making products including PGH bricks, Monier roofing and Gyprock plasterboard fell 6 per cent last month.

Julie Coates said better diversification in the range of products which CSR supplies to the construction industry along with robust cost-cutting of $20 million helped the company deliver a slight lift in profit and margins in the six months ended September 30 in building materials. But profits in its smaller aluminium business were crunched by COVID-19 economic fallout.