Air-Drying Slabs in the Southeast & Caribbean for Epoxy

Air-Drying Live-Edge Slabs in Warm, Humid Climates

Building custom epoxy river tables requires lumber that is stable and thoroughly dried. When wood is not properly dried before resin casting, subsequent shrinkage creates severe shear stress along the resin joint, risking cracks, warping, checking, and delamination. According to the USDA Forest Products Laboratory in the Wood Handbook (FPL-GTR-282), wood must be relatively dry before gluing, fastening, or applying finishes to eliminate the harmful effects of uncontrolled drying.

For woodworkers in the Southeast and Caribbean, outdoor air drying is often the first step in processing green live-edge slabs. However, local climate conditions dictate how dry that timber can actually get outdoors.

Southeast and Caribbean Outdoor Equilibrium Moisture Content

Equilibrium moisture content (EMC) is the moisture level wood reaches when exposed to surrounding temperature and relative humidity for an extended period. Table 13-1 of the Wood Handbook compiles outdoor EMC figures based on averages of 30 or more years of NOAA data.

These 30-year monthly averages reveal substantial differences between seasons across the region:

• Best drying months: Spring generally offers the lowest outdoor EMC across the Southeast. April records the lowest values in Atlanta, GA (11.8%), Charleston, SC (11.6%), and Miami, FL (12.2%). In Memphis, TN and San Juan, PR, the lowest monthly EMC occurs in March, reaching 12.2% and 12.5%, respectively.
• Worst drying months: Late summer, autumn, and mid-winter bring peak moisture levels. Outdoor EMC climbs to its highest in August for Atlanta (13.5%) and Charleston (14.5%). Miami peaks in September at 14.4%. In Memphis, the highest average hits 13.4% in both December and January. In San Juan, peak values reach 13.9% in November and December.

Outdoor equilibrium moisture content (%), USDA Wood Handbook (FPL-GTR-282) Table 13-1 (averages of 30 or more years of NOAA data).

City	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Low	High
Atlanta, GA	13.3	12.5	12.2	11.8	12.3	12.7	13.4	13.5	13.5	12.9	12.8	13.2	11.8	13.5
Charleston, SC	13.7	13.1	12.2	11.6	12.7	13.3	14.3	14.5	14.3	13.7	13.2	13.8	11.6	14.5
Miami, FL	13.5	13.1	12.7	12.2	12.5	13.7	13.4	13.8	14.4	13.8	13.6	13.5	12.2	14.4
Memphis, TN	13.4	12.9	12.2	12.2	12.7	12.6	12.9	12.8	13.0	12.5	12.8	13.4	12.2	13.4
San Juan, PR	13.7	13.2	12.5	12.6	13.3	13.1	13.4	13.5	13.7	13.6	13.9	13.9	12.5	13.9

Why Outdoor Air Drying Alone Is Never Enough

A common pitfall in river table fabrication is assuming a slab that has sat outside for years is ready for resin. Outdoor air drying alone cannot bring wood down to the required interior targets.

Table 13-2 of the Wood Handbook lists recommended moisture content values for interior woodwork, furniture, and wood trim:

• Most areas of the United States: 8% average (individual pieces 6–10%)
• Dry southwestern area: 6% average (individual pieces 4–9%)
• Damp, warm coastal area: 11% average (individual pieces 8–13%)
• General furniture and millwork range: 7% to 9%

Comparing these interior benchmarks to outdoor data highlights the gap. In Atlanta, outdoor EMC never drops below 11.8%. In Charleston, the annual low is 11.6%, while Miami reaches no lower than 12.2% and San Juan bottoms out at 12.5%. Even in damp coastal zones where the interior target is 11%, outdoor air in summer pushes wood well beyond that threshold, reaching 14.3% to 14.5%.

If a slab is poured with epoxy while balanced to outdoor humidity in the Southeast, bringing the finished table into an air-conditioned or heated home causes the timber to lose substantial moisture until it balances around 8% (or 6% in dry zones). That internal wood movement places relentless shear forces against the cured epoxy. For this reason, outdoor air drying must be followed by indoor climate conditioning, a dehumidification setup, or kiln drying before pouring epoxy.

Air-Drying Timelines and Realities

Air drying remains a valuable, cost-effective initial step to shed free water before final conditioning. The Wood Handbook notes that air drying time to reach 20% to 25% moisture content varies widely based on species, thickness, yard location, and time of stacking.

For 25-mm- (1-in.-) thick lumber, drying extremes range from:

• 15 to 30 days: Low-density species (such as pine, spruce, red alder, and soft maple) stacked in favorable locations during favorable times of the year.
• 200 to 300 days: Slow-drying species (such as sinker hemlock, pine, oak, and birch) stacked in unfavorable northern conditions.

Because live-edge slabs used for river tables are typically far thicker than 25-mm lumber, air drying down to 20% to 25% takes patience. Slower drying carries risks, as extended damp periods can encourage fungal and chemical stains. Once slabs reach that 20% to 25% threshold outdoors, move them into an enclosed, heated shop or kiln to reach the 8% interior average before starting your epoxy prep and following your resin maker’s technical data sheet.

Sources

• USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-282, 2021)

Published October 28, 2026. Sources are linked in the text.

Header image: original graphic by BigEpoxy.com.