A curable coating composition precursor comprising: (a) a first part (A) comprising (i) at least one amine epoxy curing agent based on a phenolic lipid, and (ii) inorganic microspheres; and (b) a second part (B) comprising (i) at least one epoxy resin, (ii) optionally, at least one reactive diluent, (iii) at least one epoxy reactive flexibilizer, and (iv) inorganic microspheres. The curable coating composition precursor comprises at least one fire retardant compound in part (A) and/or part (B), and the curable coating composition obtained by combining part (A) and part (B) has a density of less than 0.7 g/cm3.