Gypsum fiber board and method for producing gypsum fiber boards

A method for producing gypsum fiber boards, comprising the steps of:

• preparing a compressible mat of gypsum-containing material from a mixture comprising 75 wt % to 90 wt %, relative to the total dry mix, of calcium sulfate hemi-hydrate and 10 wt % to 25 wt %, relative to the total dry mix, of paper fibers, wherein the calcium sulfate hemi-hydrate is a mixture of α-calcium sulfate hemi-hydrate and β-calcium sulfate hemi-hydrate, wherein the content of α-calcium sulfate hemi-hydrate in the mixture is at least 10 wt %, relative to the total calcium sulfate hemi-hydrate;
• moving the dry compressible mat of gypsum-containing material on a conveyor belt to a hydration water tank, and
• hydrating the gypsum-containing material with hydration water added from above to the top surface of the mat in excess prior to passing the gypsum-containing material through a continuous press to form an endless gypsum fiber board having a thickness greater than 19 mm.