In the discussion and charts of this section, Simpson Strong-Tie presents a three-step system to determine which product coatings and base metals to use in a range of corrosion conditions. These are general guidelines that may not consider all relevant application criteria. Refer to product-specific information for additional guidance.
Simpson Strong-Tie evaluated the AWPA Use Categories (See AWPA U1-16) and ICC-ES AC257 Exposure Conditions and developed a set of corrosion resistance recommendations. These recommendations address the coating systems and materials used by Simpson Strong-Tie for fastener, connector and anchor products. Although the AWPA Use Categories and ICC-ES AC257 Exposure Conditions specifically address treated-wood applications and some common corrosion agents, Simpson Strong-Tie believes that its recommendations may be applied more generally to other application conditions, insofar as the service environments discussed are similar. You should consult with a corrosion engineer concerning the application where advisable.
To determine the appropriate classification, please refer to the Corrosion Resistance Classification table on the General Corrosion Information page.
Simpson Strong-Tie is aware of problems regarding concrete spalling and corrosion around the perimeter of some homes in the State of Hawaii, related to certain concrete embedded products made by multiple manufacturers, including Simpson Strong-Tie. The specific Simpson Strong-Tie products include STHD/LSTHD strap-tie holdowns and MAS/MASA mudsill anchors. We have investigated these products extensively and do not believe any defect in their design or manufacture is the cause of the problems. Information gathered to date indicates it is a minority of strap-tie holdowns and mudsill anchors that are experiencing the corrosion problem. Nonetheless, Simpson Strong-Tie takes these instances seriously and is investigating the cause of corrosion with these embedded products.
At this time, we have not yet been able to determine a definitive underlying cause for the corrosion on these homes. In general, we have identified a number of factors that may cause corrosion in the embedded products, including: misinstallation, the local environment, and construction practices and materials. In some instances, non-Simpson Strong-Tie metal products in contact with the foundation, such as bottom tracks and reinforcing bar, are also experiencing corrosion. For additional information on corrosion and corrosion resistance of Simpson Strong-Tie products, please go to strongtie.com/corrosioninformation.
Until better guidance can be provided to the Hawaii construction industry about how to avoid corrosion of strap-tie holdowns and mudsill anchors, Simpson Strong-Tie recommends builders work closely with their specifiers and corrosion experts to make sure they understand the corrosion issues that may present themselves on any given project. Our company, along with other manufacturers, offers alternative interior products which have not experienced spalling or corrosion issues. It may be more appropriate to use those products until a more definitive answer is available for the corrosion issues with the STHD/LSTHD strap-tie holdowns, and MAS/MASA mudsill anchors in Hawaii.
If you have additional questions or need further assistance regarding this matter, please contact our Hawaii representative at (808) 479-1216 or the Simpson Strong-Tie Engineering department at (800) 999-5099.