The present invention relates to, inter alia, methods for the treatment of wallboards with fungicides and the treated wallboards. In particular, the invention relates to the treatment of wallboards with a fungicidally effective amount of fludioxonil. The invention also provides for the treatment of wallboards with synergistic combinations of fludioxonil and other fungicides. The invention also provides the treatment of building materials with fludioxonil and synergistic mixtures containing fludioxonil.