ROOF DECKS QUICKLY CORRODED BY INSULATION (safety alert)
By: Chuck Marvin, RRC and Bruce Byrne, Sr. Consultant
Originally Published in Interface -January 2011
The roof industry potentially has another “phenolic foam” situation on its hands. Unlike the phenolic challenge from the 1980s and 1990s, today’s damage involves a different insulation corroding metal decks within a few years of original construction. For the corrosion to occur leaks do not need to be present. The dynamics have been known for over 13 years in non-roof related industries. Through the process of managing a client’s assets in Southeast Florida, we found ourselves researching and uncovering a potentially devastating condition.
Bruce Byrne, senior roof consultant for Roof Solutions Incorporated (RSI), was performing routine inspections last year on a group of buildings ranging in age from 6 to 8 years old. The metal decking was observed to be severely corroded on one building in the portfolio. A similar building in the same area had been inspected for a New York client in 2007 during a due diligence survey before procurement. This building required a roof replacement due to the deck’s deteriorated condition. A third building has since been identified with the same construction and deck condition.
We now have experience with three buildings, all well under 10 years of age with severely corroded metal decks. Portions of these decks were completely rusted through. These three buildings were constructed within a couple of years of each other using the same construction materials: A mechanically attached TPO single ply directly over 1” of wood fiber insulation. In warm states such as Florida, Texas, and California this inexpensive construction is utilized in large warehouses not equipped with air conditioning.
It is our opinion this information needs to be released industry wide. We have heard one industry associate note this condition, but no connection was made. We hope this information helps others in assisting clients. At this time selected portions of our research and findings are being released from our report. The manufacturer’s name is omitted for example due to the current warranty and legal status. The following is otherwise directly from our report:
FINDINGS IN SUMMARY:
The corrosion of the metal decking has been found to be associated with the leaching of the element chlorine from the wood fiber insulation that was originally installed in the roof system when these buildings were erected.
SUPPORTING RESEARCH & FINDINGS:
RSI utilized a recognized metallurgical testing laboratory to analyze the TPO membrane, insulation, and metal deck. This metallurgical testing laboratory originally theorized that the chlorine was introduced into the roof assembly by an outside source. Possible contamination was originally thought to have occurred during the cleaning of the top surface of the roof membrane in which the cleaning process might have utilized a chlorine based product. RSI researched this theory but could find no evidence that any such cleaning process was ever conducted by ownership, the tenants, the original builder, or the roofing contractors (either the original installer or maintenance contractor).
Environmental and manufacturing sources of chlorine within the building and in the surrounding geographical areas were scrutinized by RSI. Our research team could find no manufacturing sources within the building, nor could we find any in the geographical area that could be contributive to these levels of chlorine being found. No environmental sources were found to be contributive to the levels of chlorine being found.
As a result additional roof samples were sent in for further testing. These samples were not as deteriorated as the original samples:
A quick synopsis of the bagasse product: after the stalks of the sugarcane are crushed to extract their juice (for the production of sugar products) an organic fibrous residue remains. This fibrous residue is known as bagasse (pronounced ba-gass). The bagasse would be transported (trucked) from the surrounding sugar cane refineries to the plant for production into wood fiber insulation boards. The bagasse was stock piled unprotected in open fields surrounding the plant, and when it was needed for production purposes it would be moved onto conveyor belts that would transport the raw material into the factory for subsequent production (see photo attached).
In our subsequent investigation we became aware that liquid chlorine was applied to the bagasse during its storage to kill the microbial growth, which resulted from the rapid development of mold in the sugar-cane due to high levels of sugar, water, and heat in the bagasse. The molding phenomena in bagasse is rampant and can lead to an interstitial lung disease called bagassosis.
Cane-based fiberboard has been used extensively in various Department of Energy (DOE) packages as a thermal insulator and impact absorber. Cane-based fiberboard was only manufactured in one plant located in Louisiana. However, this fiberboard plant shut down in early 2007 due to the impact of Hurricane Katrina and other economic factors. Therefore, cane-based fiberboard is no longer available for use in the manufacture of new shipping packaging.
Current consolidation plans for the Department of Energy complex require the procurement of several thousand new Model 9975 shipping packages requiring cane-based fiberboard. Therefore, an alternative to cane-based fiberboard is needed. The manufacturer in question currently produces fiberboard from other cellulosic materials, such as hardwood and softwood.
CONCLUSION & DISCUSSION
The above extract from our report addresses only one situation. We now understand the source of the corrosion. The catalyst leading to the deck corrosion was not as clear. With phenolic insulation water was required. Phenolic insulation was typically used to obtain high thermal resistance values in climatically controlled buildings. Water entering through roof leaks was required for the phenolic insulation to start corroding the decks. In our case, the deck was corroded where leaks occurred, but the catalyst could not exclusively be roof membrane leaks.
The three relatively new buildings identified to date were not chronic leakers. We found the deteriorated deck conditions to be widespread and often located away from any roof leaks. In addition to specific assembly components, the three buildings had another thing in common: they were not air conditioned. The air was often hot and humid. It is logical to assume convection would allow the wood fiber exposure to continual moisture. It is our opinion that leaks or continual exposure to high levels of humidity will provide the catalyst for corrosion.
What is not known is the effect, if any, when this wood fiber is used as a cover board even in climatically controlled buildings. Will continuously high humidity be enough to allow the chlorine to reach the deck? This wood fiber was also a popular recover board. We are of the opinion roof leaks will prove to be a strong enough catalyst in future years to promote deck deterioration. This of course is not proven and one reason we have chosen to release this information to RCI, Inc. Other constructions using this material need to be evaluated as the years pass and leaks develop.
RECOMMENDATION & CAUTION
We encourage all firms to identify where possible the use of sugar cane based wood fiber insulation in past designs or in the assets they manage. Although roof performance is an issue, the main emphasis here is safety. In one of our three buildings a dozen areas required immediate replacement due to the potential for falling through the roof. One of the three buildings had its deck painted in recent years making corrosion difficult to spot. We suggest RCI Inc. consider acting as a central clearing house for future reporting and data accumulation.
Note to Readers: Due to the pending status of the buildings cited in this report names, scientific data, and reports are being suppressed. However, the names and authorities cited as sources have their full reports published on-line for review by the public. You are encouraged to read this data.
**After the article was originally published, conversations with the Wood Fiber Board Industry resulted in the decision to make all future references to this product be referred to as “cane-fiber-board”. This will effectively distinguish the two types in future discussions.
- Preliminary Investigation into the Corrosion of Beryllium Exposed to Celotex and Water – 1997 – MST-6, Los Alamos National Laboratory, NM
- Characterization of Celotex and Thermodynamic Calculations of the Formation of Corrosion Precursors on Beryllium – 1999 – Amarillo National Resource Center for Plutonium, UT, TX
- Leaching of chlorine from Celotex packaging in stainless steel containers storing plutonium pits – 2000 – Nuclear Engineering Teaching Lab, UT, TX
- QC Metallurgical Report – April 23, 2010
- Hostile Environment, Hogan, Lyle, Interface June 1995