The smell of mold or appearance of fungal growth on wood beneath the porch is an indication of deficient air circulation and that conditions exist for wood decay. Recent changes that can contribute to deterioration should be identified for correction, such as a clothes dryer vent dumping warm moist air underneath the deck. Preservation Brief 45: Preserving Historic Wood Porches. Wood Selection: Home > How to Preserve > Preservation Briefs > 45 Wooden Porches.