Abstract: A building board comprises a core of gypsum which has penetrated a glass fiber sheet embedded in one face and a coating of gypsum integral with the core material which has passed through the sheet. An apparatus for making such a board includes; a lower forming surface and an upper forming surface defining a forming zone between them in which the plasterboard is formed. A supply of a first slurry is provided to the lower forming surface. A supply of a second slurry is provided to a glass fiber sheet to coat the upper surface of the sheet with the second slurry. A device is provided for passing the coated sheet into the forming space, whereby the lower surface of the sheet contacts the upper surface of the first slurry. A vibrator roller is provided for vibrating the upper forming surface so that the first slurry passes through the sheet into the second slurry. A method of making the board is also disclosed.