We always hear about wind-driven rain damage, but it’s really hard to study in the field. When doing post-disaster investigations after a hurricane, we keep our distance and stay at the sidewalk so we rarely get to see what goes on inside a home. Sometimes the piles of carpet and drywall debris on the curb give a hint, but there’s always the question of whether that was caused by water entry through the roof, windows, or doors, or whether it was surge or flooding damage for those homes closest to the water.

Luckily, the IBHS Research Center helps us fill in the knowledge gaps. Our first wind-driven rain test took place in the summer of 2011. We tested a duplex where one side had a sealed roof deck, as required by the FORTIFIED Home™ Roof standards, and the other did not. When we turned on the wind and rain you can imagine what happened—the side without the sealed roof deck had water streaming in from light fixtures, wet drywall and insulation, the furniture was ruined, and the ceiling collapsed. The other side needed minor clean-up. In fact, a few adjusters from our member companies came in to assess the damage. From their estimates, the wet side of the building would have cost our members three times more to fix than the dry side. All for an investment of about $500 to add the sealed roof deck.

Most people recall this demo when they think about wind-driven rain research at IBHS, but the moment that stands out most in my mind came in 2014 when we conducted tests that compared water entry rates for various sealed roof deck configurations and no sealed roof deck at all. In the test chamber we typically run 15-minute test records, but in our very first run of the unsealed roof, my project partner Dr. Steve Quarles, started yelling over the radio for me to stop the test. With no sealed roof deck, we overflowed the water collection tubs in about three minutes. The study ultimately found that a sealed roof deck can reduce water entry into a home by as much as 95% compared to a bare, unsealed roof deck.

The IBHS FORTIFIED Home program essentially assumes that a roof cover will be lost in a significant high-wind event. When that happens, the sealed roof deck is the back-up plan, which is why it is required to get a FORTIFIED Roof. Water in means costly repairs, prolonged displacement, and ruined personal belongings. Keeping the water out means a family can return quickly and resume life.

 

Tanya Brown-Giammanco, PhD

Managing Director of Research