A method for the manufacture of a building board, wherein: - sheet-like preforms, which comprise support material and filler material, of which the support material contains natural fibre material, textile fibres, polyester and/or polypropylene and the filler material contains fibrous or fine-grained natural material, namely peat, pulp, hemp or coconut fibre, are compressed into a number of sheet-like pressed products (2, 3, 4), which have a density (ρ1, ρ2, ρ3) and thickness (S1, S2, S3); - each sheet-like pressed product (2, 3, 4) is pre-treated by applying contact adhesive on one side or both sides of each sheet-like pressed product (2, 3, 4), and the adhesive is allowed to harden completely or partially; - the pre-treated pressed products (2, 3, 4) are placed against each other to form a layer structure so that those sheet-like pressed products (2, 3, 4) onto which adhesive has been applied on both sides come to the inside of the layer structure and those sheet-like pressed products (2, 3, 4) onto which adhesive has been applied on one side only are placed at the outer edges of the layer structure so that the side onto which adhesive has been applied points to the inside of the layer structure; - the layer structure is compressed at an elevated temperature, which is lower than the melting temperature of the support material, in order to accomplish a shock compression effect by compressing the layer structure 5 - 40% thinner than its original total thickness; - compression is reduced before the channelling of the adhesive -i.e. before the expansion of the pressed products (2, 3, 4) and of the contact adhesive to the sides when the layer structure is compressed- and the compression reduced in this way is continued at an elevated temperature until the adhesive activates and forms an essentially solid bond from the layer structure, in which case the pressed products (2, 3, 4) in the layer structure have essentially been fastened to each other forming the building board; - compression is finished and the building board is allowed to cool. - sheet-like preforms, which comprise support material and filler material, of which the support material contains natural fibre material, textile fibres, polyester and/or polypropylene and the filler material contains fibrous or fine-grained natural material, namely peat, pulp, hemp or coconut fibre, are compressed into a number of sheet-like pressed products (2, 3, 4), which have a density (ρ1, ρ2, ρ3) and thickness (S1, S2, S3); - each sheet-like pressed product (2, 3, 4) is pre-treated by applying contact adhesive on one side or both sides of each sheet-like pressed product (2, 3, 4), and the adhesive is allowed to harden completely or partially; - the pre-treated pressed products (2, 3, 4) are placed against each other to form a layer structure so that those sheet-like pressed products (2, 3, 4) onto which adhesive has been applied on both sides come to the inside of the layer structure and those sheet-like pressed products (2, 3, 4) onto which adhesive has been applied on one side only are placed at the outer edges of the layer structure so that the side onto which adhesive has been applied points to the inside of the layer structure; - the layer structure is compressed at an elevated temperature, which is lower than the melting temperature of the support material, in order to accomplish a shock compression effect by compressing the layer structure 5 - 40% thinner than its original total thickness; - compression is reduced before the channelling of the adhesive -i.e. before the expansion of the pressed products (2, 3, 4) and of the contact adhesive to the sides when the layer structure is compressed- and the compression reduced in this way is continued at an elevated temperature until the adhesive activates and forms an essentially solid bond from the layer structure, in which case the pressed products (2, 3, 4) in the layer structure have essentially been fastened to each other forming the building board; - compression is finished and the building board is allowed to cool.