Flood-Hardy Upgrades With Closed-Cell SPF
How to Better Educate the Public About the Benefits of SPF in Flood Prevention
Wednesday, December 1, 2021
by: Fiona Soltes

Section: Features- Winter

For as horrific an experience as a flood can be, some things never fail: Even those who go through it firsthand have short memories, and don’t do all they can to minimize future damage.

Spray foam professionals can educate the public about better options – inspiring them to make the investment of time and money needed to reduce future damage and mold.

Now is the time to revisit a paper released by the Spray Polyurethane Foam Alliance following the monumental 2017 hurricane season. "Flood Resistant Construction Using Closed-Cell SPF" pointed out that once a home experiences a flood, it is likely to experience another. "Rebuilding a flooded home to accommodate a future flood is not only a good idea," the paper states, "it may be a requirement for certain flood insurance programs."
Ah, but there’s the rub. Claudette Reichel, EdD, director of LaHouse Resource Center in Baton Rouge, said that the current flood insurance program still "really needs to be modified to encourage greater resilience." It has been improved some, she said, "but it still doesn’t really achieve its core mission of reducing disaster loses and costs. It’s structured more like standard insurance: Just put it back like it was, with the same vulnerable materials that got ruined…. People may get enough claim funding to do that, but that is just asking for the same thing to happen again."
Spray foam professionals, then, can educate the public about better options – inspiring them to make the investment of time and money needed to reduce future damage and mold.

"That’s the message I try to hit," Reichel said. "Take control of your future. This is one way you can have control over what happens next time there’s a flood. Yes, the public sector should work to improve the infrastructure and community resilience. But there are things you can do for your own home, too."

The paper, which includes floodhardy upgrades cited by Reichel and others, notes that in many cases, "contractors will be under pressure from the homeowner or building owner to rebuild quickly. While that is well understood, it is important for contractors to do the job correctly."
The correct process includes removing all water-damaged materials from a flooded structure, such as flooring, drywall, fibrous or open-cell SPF insulations, and fiberboard or swollen OSB sheathings. A structural engineer should be consulted if removing sheathing or walls, and cross-bracing may be needed on the remaining framing.

Next, it’s important to ensure all remaining substrate surfaces are "clean, dry and clear of debris," the paper states. "A clean, dry surface is important for SPF adhesion, and good adhesion is critical for a continuous, air-tight and water-resistant assembly. Floodwaters can carry a significant number of contaminants, such as sewage, sludge and oils. Detergents and mold treatment chemicals used during cleanup may also affect adhesion. It is critical to be sure these residues are removed from all substrates."

Dehumidifiers used in conjunction with air conditioning help "speed dry" wet materials to reduce the risk of mold, Reichel added.
If sheathing is retained, closed-cell application is the next step, the paper states, using a picture framing technique to avoid shrinkage and delamination. Finally, install a code-complaint 15-minute thermal barrier over all SPF when the foam is exposed to an interior occupied space. A spray applied semipermeable acrylic paint can be applied on the surface of the closed-cell SPF to provide a more cleanable surface for washing the wall cavities after a future flood event.

Brick facades, however, introduce unique challenges, and many of the homes hit by floods in 2016 and 2017 fit that category. First, if wood or fiberboard sheathing is water-damaged and removed, there are concerns about applying the SPF directly to the clean, dried brick – and it’s important to have a drainage gap behind the brick to prevent maintenance problems. Second, many people affected by floods don’t have flood insurance, and even if they do, the payout is not enough to cover removing the brick veneer to replace sheathing.

"That was a big dilemma for people," Reichel said. "Best practice is to remove the brick veneer, replace the sheathing, put on a weather-resistant barrier system, and rebuild the brick veneer. But for most, that wasn’t reality. Few could afford to do that."

Reichel and Building Science Corporation principal Joseph Lstiburek, PhD, P.Eng, have since detailed alternative restoration systems, each one working from the inside of the structure while leaving the brick veneer in place. Two of the three methods involve the use of closed-cell spray foam. One uses closed-cell spray foam with a rainscreen product; another uses closed-cell spray foam with thin, fanfold XPS sheets; and a third is a rigid XPS foam board sheathing method. (All are explored in detail in the LaHouse Resource Center’s "FAQ’s – After Gutting Your Flooded Home," on the LSU Ag Center website, www.lsuagcenter.com/LaHouse, through the Flood Recovery link.)

Of the three, the rainscreen/closedcell foam system is the most robust, simplest and fastest option – though it is still not a standard building practice and may be more costly. It involves repairing or replacing flashing to protect the wood bottom plate and the bottom of the studs from draining water; placing rainscreen or attic ventilation baffle products against the interior of the brick veneer to maintain air and drainage space; and then using closed-cell spray foam to fill the remaining space between the studs and rainscreen, plus a 2-inch thick partial fill between studs.

The cured closed-cell spray foam provides both an airtight insulation system and structural capacity in place of the removed sheathing. Reichel said she knows an SPF contractor who created a mockup of the system and displayed it at local home shows to help spread awareness of how to build back better. Spray foam professionals could explore doing the same, she said, in addition to making available the LSU Ag Center and FEMA Wet Floodproofing publications. (They’re also available for download from the LaHouse Resource Center website.)