Excessive Crawl Space Moisture Damage


TSA was called in to investigate damage in a hotel that was constructed over expansive soils. To avoid potential foundation problems due to expansive soils, they chose to use a wood and steel framing system for the ground floor that was constructed over a crawl space. Problems followed due to three issues: The site had poor drainage, with water entering the crawl space from outside the building. The crawl space had poor ventilation, so that moisture couldn't escape. Finally, insulation was placed next to the wood framing, which trapped moisture right next to the wood, accelerating the wood rot.

Within 7 years, the elevated moisture caused collapse of portions of the structural framing. TSA recommended major repairs, including replacement of large areas of wood framing. Since wood rot typically occurs with a wood moisture content of 35-50%, TSA recommended that the wood moisture content be reduced to less than 20% through the use of improved drainage and ventilation.