Insulating values of a perlite concrete roof deck depends on the density of the concrete mix that is prepared. Typical U values range from ( W/m².k) for a (50 mm)(350kg/m³) to ( W/ m².k) for a (100 mm) thick roof deck. Fire Ratings: There are a number of different perlite concrete roof deck designs that offer fire ratings from 1 hour to 3 hours. A typical 3hours rated roof deck ...