Everbuild evbevfire firefoam b1 is a quick setting one part polyurethane foam with fire retardant properties the foam expands on application to up to 50 times its original volume and meets the extremely stringent requirements of din 4102 part 1 for construction materials class b and bs476 part 20 1987 where fire ratings of 30 mins to 35 hours are achievable once cured the foam can be cut sawn or plastered over after only one hour providing the working temperatures can and surfaces are between