The choice of materials for repairs and retrofits has a major influence on the strength, appearance, and durability of a house. A few extra dollars spent on quality materials pays off in the long run.
Hardware, such as nails, screws, bolts, and tie rods should be either hot-dip galvanized or made of stainless steel. Introduction of untreated steel elements should be avoided as these are highly prone to rust and more rapid deterioration. Ordinary zinc electroplating, a common coating on hardware, is different from hot-dip galvanizing and is not durable enough for historic homes in Louisiana, especially those located on the coast.
Likewise, anchors embedded in masonry or existing concrete should be hot-dip galvanized or stainless steel. On the coast, a best practice is to use stainless steel rebar or stainless wire mesh for reinforcement in concrete footings and slabs. Such reinforcement is expensive, but will never corrode. Costs can be offset somewhat by placing it closer to the surface than normal and using the bare minimum reinforcement.
For off-the-shelf wood fasteners, buy hardware that uses the manufacturers’ highest level of corrosion protection. For custom steel fabrications, hot-dip galvanizing is preferable and should be done after all cutting, drilling, and welding is complete to avoid gaps in corrosion protection. Series 5000 aluminum is a good choice for corrosion resistant fabrications.
Wood should always be either preservative-treated southern pine or the heartwood of a naturally durable species. Non-durable wood species such as white pine, poplar, fir, or untreated southern pine should only be used in locations where they are protected from moisture and humidity and should not be placed in contact with the ground.
According to Secretary of Interior Standard’s priority should be given to retaining historic materials. If materials are damaged or deteriorated it is better to repair than to replace. When replacement is the only option it should be done by in-kind materials that have the same characteristics and material properties. By using in-kind materials for replacement over time the materials will age and act similarly to the environment.
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