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Guidelines for Selecting the Proper Materials and Coatings
for Connectors For Wood Construction
and Anchoring and Fastening Systems for Concrete and Masonry
1 Evaluate the Application
Consider the type of structure and how it will be used. These recommendations may not apply to non-structural applications such as fences.
2 Evaluate the Environment
Testing and experience indicate that indoor dry environments are less corrosive than outdoor environments. Determining the type of environment where a product will be used is an important factor in selecting the most appropriate material and coating for use. To help in your decision making, consider the following general exposure information:
Interior Dry: Includes wall and ceiling cavities, and raised floor applications in enclosed buildings that have been designed to ensure that condensation and other sources of moisture do not develop.
Exterior Dry: Includes outdoor installations in low rainfall environments and no regular exposure to moisture.
Exterior Wet: Includes outdoor installations in higher moisture and rainfall environments.
Higher Exposure Use: Includes exposure to ocean salt air, de-icing salts, fire retardants, large bodies of water (e.g., dock boards), fumes, fertilizers, soil, some preservative treated woods, industrial zones, acid rain, and other corrosive elements.
3 Evaluate the material to be used
When metal is in contact with most untreated wood and other common building materials, additional corrosion risk caused by the material is not a significant factor. When fastening dissimilar metals carefully consider the correct combination of fastener and material necessary to avoid galvanic corrosion. For preservative-treated wood applications proceed to step four, otherwise proceed to step five.
4 Familiarize yourself with the preservative-treated wood to be fastened.
The preservative-treated wood supplier should provide all of the pertinent information about the wood being used. This information should include the specific type of wood treatment used, if ammonia was used in the treatment and the chemical retention level. If this information is not available, then Simpson Strong-Tie Company Inc. recommends the use of types 304, 305 or 316 stainless steel. It is also advisable to obtain a recommendation from the treated-wood supplier for a coating or material that is suitable for use with their formulation in the intended environment. If this recommendation differs from those shown in the table below, Simpson Strong-Tie Company Inc. recommends that the most conservative recommendation be followed.
5 Use the Environment/Treatment Classification Chart below to match the proper classification to the environment and base material application. Then use the appropriate Materials and Coatings Available listing to select the proper coating or material..
If a preservative-treated wood product is not identified on the chart, Simpson Strong-Tie has not evaluated test results regarding such product and therefore cannot make any recommendation other than the use of coatings/materials shown in the "high" category below. Manufacturers may independently provide test results or other product use information; Simpson Strong-Tie expresses no opinion regarding any such information.
For additional critical information please see the Preservative Treated Wood Technical Bulletin (PDF), Preservative Treated Wood Frequently Asked Questions, and General Corrosion Risks.