Abstract: The invention relates to a method for producing a building material from a mixture of unscreened thermoplastic waste and mineral, preferably mineral aggregate. The crushed and/or screened mineral and plastic waste are washed, whereafter the mineral is heated to a predetermined temperature, and a given amount of plastic granules or plastic flakes made from the unscreened thermoplastic waste is mixed with the heated mineral aggregate. In the dosing and/or scattering stage, heated fine-grained filler mineral aggregate is further added to the resulting mass. The mass is dosed or scattered on a coating material, and the building marterial is pressed by compression moulding or flat-pressing and/or calendering to final thickness into slabs, blocks, bricks or boards. Applications include for example insulation boards used in soil mechanics, paving slabs or bricks, concrete formwork boards or blocks, noise and sight barrier elements, fire-, sound- and moisture-proofing slabs.