Abstract: A sheathing system is provided for covering structure of a building. The system includes elongated panels that can be arranged edge to edge to form a generally planar surface which can be moisture tight for convenient washing. The panels are rigidly supported from the building structure so that said generally planar surface does not move if subjected to the pressure of a jet of water. The panels can run transversely to rigid elongated stringers which are spaced from the building structure so that they can clear irregularities on the building structure. Between such stringers and the building structure are spacers that are of relatively short length measured along the lengths of the stringers, and that can slide along the stringers to suitable locations for connection to the building structure. The spacers may be rigid spacers.