A bond is created between a gypsum matrix and titanium or zirconium based coupling coating applied onto a glass fiber during gypsum board cure. The commercially available titanium or zirconium based coupling has a generic formula of the type [RO-}-nTi--[--OXR'Y]4-n or [RO-}-nZr--[--OXR'Y]4-n. These coupling compositions chemically bond to glass fibers by replacing the --OH groups present on the glass fibers in aqueous solutions with Ti--O or Zr--O bonds. In order to bond with calcium ions in hydrated gypsum crystals, the X functionality is selected to be a phosphate or pyrophosphato group. The bond between the glass fiber and the titanium or zirconium based coupling composition is due to the formation of a monolayer, while the bond between the hydrated gypsum crystal and the coupling composition is intermittent due the acicular structure of gypsum crystals. The titanium or zirconium based coupling composition coating on glass fibers bonded to the gypsum matrix results in load transfer between the gypsum matrix and the glass fibers, resulting in improved flexure strength and nail pullout resistance. The Titanate/Zirconate can also be used as a board mechanical properties enhancing agent without addition of glass fiber.