47.5 MB - The Whole Building Design Guide

steel. FEMA Technical Bulletin, CorrosionProtection for Metal Connectors in Coastal Areas(FIA-TB-8, 1996) contains information oncorrosion protection. Attention also needsto be given to dry rot avoidance, for example,by specifying preservative-treatedwood or developing details that avoid excessivemoisture accumulation. Appendix Jof the Coastal Construction Manual, (FEMA55, 2000) presents information on wooddurability.Coastal environments are conducive tometal corrosion, especially in buildingswithin 3,000 feet of the ocean. Mostjurisdictions require metal buildinghardware to be hot-dipped galvanizedor stainless steel. Some local codesrequire protective coatings that are thickerthan typical “off-the-shelf” products. Forexample, a G90 zinc coating (0.75 milon each face) may be required. Otherrecommendations include the following:Durable materials are particularly importantfor components that are inaccessibleand cannot be inspected regularly (such asfasteners used to attach roof insulation).Special attention also needs to be given todetails. For example, details that do notallow water to stand at connections or sillsare preferred. Without special attention tomaterial selection and details, the demandson maintenance and repair will be increased,along with the likelihood of failureof components during high winds.Water infiltration (rain): Although preventionof building collapse and major buildingdamage is the primary goal of wind-resistantdesign, consideration should also begiven to minimizing water damage and subsequentdevelopment of mold from thepenetration of wind-driven rain. To the extentpossible, non-load-bearing walls anddoor and window frames should be designedin accordance with rain-screenprinciples. With this approach, it is assumedthat some water will penetrate past the faceof the building envelope. The water is interceptedin an air-pressure equalized cavitythat provides drainage from the cavity to the outer surface ofthe building. See Sections 3.3.3.2 and 3.3.3.3, and Figure 3-40for further discussion and an example.m Use hot-dipped galvanized or stainlesssteel hardware. Reinforcing steel shouldbe fully protected from corrosion by thesurrounding material (masonry, mortar,grout, or concrete). Use galvanizedor epoxy-coated reinforcing steelin situations where the potential forcorrosion is high.m Avoid joining dissimilar metals,especially those with high galvanicpotential.m Avoid using certain wood preservativesin direct contact with galvanized metal.Verify that wood treatment is suitablefor use with galvanized metal, or usestainless steel.m Metal-plate-connected trusses shouldnot be exposed to the elements. Trussjoints near vent openings are moresusceptible to corrosion and mayrequire increased corrosion protection.Note: Although more resistant than othermetals, stainless steel is still subject tocorrosion.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-39