Study Reveals Reasons for Water Intrusion
By Edie Ousley
A forensic investigation (download full report) by one of the nation’s foremost building-science engineers has identified multiple and interrelated reasons why water intrusion occurred in homes after Florida’s four hurricanes in the summer and fall of 2004.
The report specifically addresses the performance of construction materials, and provides recommended changes to Florida’s Building Code as well as building practices. The report indicates that the water management capacity of exterior wall assemblies – normally able to handle penetrating rainwater – were “overwhelmed” by unprecedented and “extraordinary weather events.”
A report on the investigation, released today jointly by the Florida Home Builders Association and the Home Builders Association of Metro Orlando, offers a series of recommended changes to the Florida Building Code as well as to building practices to improve the water management performance of residential structures.
The investigation was conducted by Dr. Joseph Lstiburek, a principal of Building Science Corp. in Westford, MA, and one of the nation’s foremost scientists in the field of building construction.
Dr. Lstiburek’s report was delivered by FHBA representatives on Tuesday to the office of Florida Governor Jeb Bush and it will be distributed to members of Florida’s Building Commission and Florida Senate President Tom Lee and Speaker of the House Allan Bense to assist them in their consideration of Dr. Lstiberek’s proposed code changes.
“We embrace Dr. Lstiburek’s report. It is a frank, candid and thorough assessment of the complex and multiple causes of water intrusion,” said Dan Gilmore, President of the Florida Home Builders Association. “As you read it, it becomes clear that the science speaks for itself. We firmly believe that Dr. Lstiburek’s report puts to rest the unfounded speculation that has circulated around this issue for the past several months.”
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 Mass Assembly Current (click to enlarge) |
 Mass Assembly Best (click to enlarge) | |
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 Mass Assembly Window Current (click to enlarge) |
 Mass Assembly Window Best (click to enlarge) | |
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 Soffit Vent Current (click to enlarge) |
 Soffit Vent Best (click to enlarge) |
“Under normal conditions, the amount of penetrating rainwater through stucco into a masonry block wall is minor and easily absorbed, redistributed and released to both the interior and exterior,” Dr. Lstiburek writes in his investigative report.
“August and September 2004 was not a normal time,” he continues. “The mass assemblies were overwhelmed due to the extraordinary weather events … (and) not able to store the quantity of penetrating water and not able to dry rapidly enough between wetting events…”
Typical paint finishes are unable to “span” micro-cracks, Dr. Lstiburek writes. “Under normal conditions, this is not an issue… (due to) the huge moisture storage capacity of masonry block assemblies. As stucco buildings age and are successively repainted, the water entry is reduced after each layer of paint is added. In general, this is why many older buildings with mas(onry) walls performed somewhat better.”
Among his recommendations for improving the water management capacity of exterior wall assemblies, Dr. Lstiburek proposes that builders:
- Add a “seat” to the base of masonry wall assemblies, providing a small channel where penetrating water can be temporarily stored during extended periods of excessive wind-driven rain.
- Improve the performance of water-resistant barriers (used in second-floor assemblies between stucco coatings and interior walls) by ensuring a “bond break” so that there is adequate room for penetrating moisture to drain.
- Work with building code officials to change the approved method of joining first- and second-floor exterior wall assemblies. Current building codes require builders to use “reverse flashing” rather than ensuring that penetrating rainwater is expelled to a structure’s exterior.
Dr. Lstiburek also identifies a number of additional entry points for penetrating rain, including windows, doors, vented soffits, attic vents, electrical panels and vent fan hoods. He further recommends that the Florida Building Code be revised to add water management requirements for each potential point of entry.
Jack Glenn, FHBA’s Director of Technical Services and FHBA’s in-house building code expert, said the association pledges to work with local and state regulators to develop necessary changes to Florida’s Building Code and on education programs needed to disseminate the recommendation in Dr. Lstiburek’s report.
“We have an education process ahead of us,” Glenn said. “It’s going to be a major effort, requiring the participation of many people inside and outside our industry to first codify these recommendations and then train building inspectors and home builders on how to increase the water management capacity of mass wall assemblies. Fortunately, we’ve been given a great start by Dr. Lsitburek and his team.”
About the FHBA
The Florida Home Builders Association is a Tallahassee, Florida-based trade association representing more than 17,500 corporate members involved in Florida’s home building and remodeling industry. Known as “the voice of Florida’s housing industry,” FHBA is affiliated with 28 local home builders associations throughout Florida. FHBA members employ 473,000 Floridians and contribute $42 billion annually to the state’s economy – making home building Florida’s second largest industry. The Florida Home Builders Association – caring, creating, and contributing. Visit us on the web at www.fhba.com.
About HBA of Metro Orlando
Established in 1953, the Home Builders Association of Metro Orlando is a trade organization comprised of more than 1,400 member businesses, representing over 37,000 employees. On behalf of its members, the HBA conducts continuing education programs, provides legislative representation, and interacts with governmental agencies. The Mid-Florida Home Builders Foundation, the charitable arm of the HBA, is dedicated to raising funds for organizations that help children and families in need and is responsible for donations of over $1 million to youth-related charities across Central Florida.
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