Novel, one-part polymer grout compositions are provided comprising a silanated polymer. The inventive grout compositions can thus be water and/or stain resistant to a greater degree than conventional one-part polymer grouts. In some embodiments, the grout compositions may also have enhanced shrinkage and/or crack resistance, as may be provided at least in part by the inclusion of an amount of one or more fiber fillers. As a result of these advantageous properties, the one-part polymer grout compositions provided herein may find applicability in environments previously contraindicated for conventional one-part polymer grout compositions, e.g., in horizontal and/or damp, or even wet, environments, or in combination with certain tile materials, e.g. water absorbing tile materials.