Question

EQUILIBRIUM MOISTURE CONTENT: White oak flooring is dried to 5% moisture content. After kiln drying and machining, it is stored in a warehouse for 5 months. The warehouse averages 80˚F and 75% RH for these months. Answer the following:

Will the oak flooring expand or contract?
What would the oak flooring's moisture content be at the end of the 5-month period?
EQUILIBRIUM MOISTURE CONTENT: The bottom chord of a truss is made up of largely juvenile wood. During the winter, it is covered with insulation and heated by the space below. The conditions are about 70˚F and 20% RH for this location in the winter. During the summer, the conditions change to 75˚F and 85% RH. The homeowners have complained that there is a gap of ½" at the partition walls, but that gap disappears in the summer. How will the moisture content of the bottom truss chord change, winter to summer? [HINT: find the EMC of the wood in the winter and summer, and calculate the difference. If you don't find the exact values in the EMC table, just pick the closest one]

Answer 1

White oak flooring stored at 80°F and 75% RH will expand while the winter conditions will cause the bottom chord of a truss made from juvenile wood to contract, resulting in a visible gap that closes as the wood expands during the humid summer.

Step-by-step explanation:

The Equilibrium Moisture Content (EMC) is crucial in understanding whether wood will expand or contract under certain temperature and humidity conditions. For white oak flooring that is dried to 5% moisture content, when stored in conditions of 80°F and 75% RH, the oak flooring is likely to expand as its moisture content will reach a balance with the environment, which is higher than the initial 5% after kiln drying.

Without exact EMC values at that specific temperature and RH provided, we can only approximate that the moisture content of the flooring would increase. It's important to consult an EMC table and look for the closest values to determine the exact increase in moisture level.

Regarding the bottom chord of a truss made from juvenile wood, the moisture content will vary between winter and summer. In the winter conditions of 70°F and 20% RH, the EMC will be lower compared to the summer conditions of 75°F and 85% RH. Due to this fluctuation in EMC from winter to summer, the wood would contract in the winter, explaining the gap at the partition walls, and then expand in the summer, closing the gap. Again, for precise EMC values, one should refer to an EMC table for wood at those specific conditions.