Abstract: An installation for the production of sheet-like members from a mixture of plaster and fibrous material comprises, in addition to a device which prepares the raw materials and mixes them in the dry state in a desired ratio, as well as a device, which adds and mixes in an accurately dosed quantity of water, a spreading device, which spreads a mat of material on a forming line. The mat of spread-out material is compacted in a continuously operating belt press. The latter comprises in known manner two endless steel belts, which are guided around two movable press plates of the belt press, which are spaced apart. The mat of spread-out material is compacted between the forming line, on which it rests, and an endless-belt screen, which bears on the upper steel belt of the belt press and thus acquires a side marked by the endless-belt screen. After being cut up by a cutting device, the individual sheets are turned through 180.degree.