The addition of a fungicide to the water repellent, which converts the WR to a WRP, further enhances the effectiveness of the finish by inhibiting the growth of mildew and decay fungi. Water repellents and WRPs also decrease the swelling and shrinking that lead to cracking and warping. They protect the painted wood from blistering. Cracking, and peeling. In wood species that contain colored water-soluble extractives, such as redwood and cedar, WRs and WRPs help reduce the discoloration caused by extractive bleed.
Wood is the material of choice for many structures.
As with any building material, the use of wood depends on its properties, such as strength and stiffness, as well as the finishing characteristics and maintenance requirements. Problems such as poor finish performance, mildew, checking and splitting, and wood decay can be controlled with proper care and maintenance. Such problems can be avoided or attenuated through knowledge about the factors that affect wood, particularly wood exposed outdoors. If wood structures are given proper care initially and are maintained periodically, they can be functional and structurally sound, as well as aesthetically pleasing, for decades. This report includes a discussion of the effects of outdoor exposure on wood, characteristics of WR and WRP formulations, and methods for applying WRs and WRPs.