PURPOSE: To reduce weight of a formed material for building materials, maintain strength and simultaneously impart soundproofing, sound insulating, sound absorbing, heat insulating and cold reserving properties thereto by mixing polystyrene grains in a cellular concrete material.

CONSTITUTION: The above-mentioned material for building materials is prepared by mixing polystyrene grains in an expanded concrete material. Perlite may also be used in place of the polystyrene grains. If a higher strength is required, a metal netlike material may be interposed in the interior thereof.