9.2 Maintenance and Replacement Considerations

Inspection of fasteners and metal connectors is important and should be a regular maintenance activity undertaken by owners of buildings located in nearshore coastal environments. Since many homeowners may not be aware of the effects of corrosion on the fasteners in their homes, communities in coastal areas should consider communicating to their citizens the importance of routine inspection and maintenance of connectors and fasteners.

In some applications, connectors may be located where they are accessible and easily maintained. In areas where corrosion is less aggressive, such as locations farther from the coast, applying a coat of exterior house paint to exposed connectors may be enough to extend the life of the connectors. In areas with more aggressive corrosion, even annual painting is unlikely to prolong the life of connectors. In these areas, accessible connectors should be inspected for corrosion and replaced when necessary. Galvanized light gauge metal connectors should be replaced as soon as corrosion extends into the base metal (see Figure 12). The presence of more than thin rusty edges indicates that the zinc coating has been consumed and the sacrificial effects have been lost. Corrosion of the thin, steel sheet will occur quickly and rapidly affect the structural integrity of the connector.

9.2.1 Replacing Corroded Connectors

Replacement is the only option in existing buildings where connectors have already been damaged by corrosion. It is recommended that replacement connectors have different sizes or shapes or be fastened in different locations so that connections are to undisturbed wood. Since the availability of locations to attach replacement connectors into undisturbed wood may be limited, it is imperative that the most corrosion-resistant connectors and fasteners possible be used to minimize replacements over the life of the structure. Inspections may also indicate a need to install connectors where they were not previously installed. For example, adding roof uplift connectors (hurricane clips) can significantly improve wind resistance and is generally worthwhile, even if some dismantling is needed to gain access. Wind retrofits are described for various levels of wind performance improvement in FEMA P-804, Wind Retrofit Guide for Residential Buildings (2010c).

9.2.2 Reducing Connection Maintenance for New and Existing Buildings

When evaluating the option of whether to initially install more corrosion-resistant metal connectors or replace them more frequently, the cost over the life of the building should be considered. Enhanced corrosion-resistant metal connectors, available for a moderately higher price, can have significantly longer lifetimes than nominally galvanized connectors. The cost of labor for initial installation is often the same for either option. The material and labor cost for even one replacement is typically many times more than the added cost of initially installing more corrosion-resistant materials. Using more corrosion-resistant materials during construction can avoid or reduce the cost of future repairs.

In areas where conditions foster aggressive corrosion and nominally galvanized connectors may have to be replaced as often as every 5 years, using more expensive materials such as stainless steel connectors and fasteners will likely prove less costly over the long run. Repeated replacement of metal connectors can be difficult since previously used fastener holes should not be reused. Different styles of metal connectors may provide different and faster locations to facilitate replacement, but eventually damage from fastener holes may result in the need for more extensive repairs such as replacing structural members to maintain a continuous load path. Replacing structural members would be more expensive than upgrading to a more corrosion-resistant metal connector that would reduce the number of necessary connector replacements over the life of the building.

Given the difficulty of inspecting many connections after construction and the impossibility of inspecting others without invasive actions, using nominally galvanized fasteners and metal connectors in corrosive areas is fraught with potential problems and higher maintenance costs. There is a low likelihood that effective regular inspections to identify deterioration before the structural integrity is compromised would or could be performed. Even when problems with more vulnerable connectors can be identified, replacing damaged connections in existing buildings is usually costly and difficult. Furthermore, many connectors are hidden structural components that will go unseen and are difficult or impossible to maintain or replace. In such cases, replacement is rarely an option, and more corrosion-resistant materials should be selected during initial construction.