The present invention relates to a curable precursor of a fire-retardant, low-density and essentially halogen-free epoxy composition comprising (i) 10 to 70 weight percent of at least one organic epoxide compound with an epoxide functionality of at least one, (ii) 1 to 55 weight percent of at least one epoxide hardener, (iii) 5 to 50 weight percent of an essentially halogen-free fire-retardant system that includes a mixture of: (1) at least one compound selected from the group comprising alkaline earth metal hydroxides and aluminium group hydroxides, and (2) at least one phosphorous-containing material, (iv) 10 to 60 weight percent of a filler system capable of reducing the density of the precursor that includes a mixture of (1) at least one low-density inorganic filler having a density of between 0.1 to 0.5 g cm−3?, (2) at least one low-density organic filler having a density of between 0.01 to 0.30 g/cm−3? and being compressible.