Lumber Storage & Acclimation
Southern Pine lumber 2″ and less in thickness must be dried to a maximum moisture content of 19% before it can be grade marked for structural use, so no further seasoning is required prior to installation. For best performance, however, all wood products should be protected from the elements at the job site and properly acclimated if necessary.
In-Service Moisture Content
Wood-frame buildings perform best when the framing lumber at enclosure is as close as possible to the moisture content it will finally reach in service. The final in-service moisture content of lumber in the building varies with the geographic region and with location in the structure. Floor joists over a crawl space may reach seasonal moisture contents in excess of 14%. Roof trusses and rafters, on the other hand, may dry below 6%.
Storage and Protection of Materials
Wood is a hygroscopic material that absorbs and releases moisture, equalizing itself with surrounding conditions. Wood products should be protected from the weather at the building site. They should be unloaded and stored in a dry place, not in wet or muddy areas. They should be elevated on stringers, not in direct contact with the ground. Wood products stored in an open area should be covered with a material that will give protection from the elements, but be porous enough to allow moisture to escape. Polyethylene or similar nonporous covers may trap moisture.
Acclimation of Finish Materials
Interior finish lumber, such as flooring and paneling, must be protected from moisture and properly acclimated indoors prior to installation. Exterior finish lumber, such as siding and porch flooring, should also be protected from moisture and allowed to properly acclimate outdoors prior to installation.