Comparing Hackberry and White Ash for Wood and Epoxy Tabletops
Selecting the right hardwood slab for an epoxy river table involves balancing mechanical strength, surface durability, and moisture-driven movement. Hackberry (Celtalis occidentalis) and White ash (Fraxinus americana) are two ring-porous domestic hardwoods frequently sourced for live-edge builds. To evaluate how both species perform under daily use and seasonal humidity changes, we can look directly at standard testing figures compiled by the USDA Forest Products Laboratory in the Wood Handbook (FPL-GTR-282).
Weight, Density, and Dent Resistance
Specific gravity indicates a wood species’ density and provides a direct baseline for tabletop weight and dent resistance. At 12% moisture content, Hackberry has a specific gravity of 0.53, while White ash comes in higher at 0.60. For large conference tables or thick slabs, White ash adds noticeable overall weight to the build.
Surface dent resistance is primarily determined by side hardness and compression perpendicular to the grain. In both metrics at 12% moisture content, White ash shows greater resistance to concentrated loads:
- Side Hardness: Hackberry measures 880 lbf, whereas White ash reaches 1,320 lbf on the Janka scale.
- Compression Perpendicular to Grain: Hackberry provides a fiber stress at proportional limit of 890 lbf/in², compared to 1,160 lbf/in² for White ash.
White ash offers higher baseline protection against heavy dropped objects and clamping pressure, while Hackberry provides moderate hardness suitable for residential dining or accent tables.
Stiffness, Strength, and Span Capacity
When engineering tables with cantilevered ends, unsupported seating overhangs, or long spans between trestle legs, modulus of elasticity (MOE) and modulus of rupture (MOR) dictate how much the wood will deflect and what bending load it can support.
At 12% moisture content, White ash displays a modulus of elasticity of 1.74 million lbf/in² and a modulus of rupture of 15,400 lbf/in². Hackberry tests lower in both properties, with an MOE of 1.19 million lbf/in² and an MOR of 11,000 lbf/in². White ash also displays higher shear strength parallel to grain at 1,910 lbf/in² compared to 1,590 lbf/in² for Hackberry. Because White ash is stiffer, wide unsupported spans will deflect less under static table loads than identical dimensions of Hackberry.
Figures from the USDA Wood Handbook (FPL-GTR-282), Tables 4-1, 4-3, 5-3b, 13-5 and 14-1. Clear, straight-grained specimens; real slabs vary.
| Property | Hackberry | White ash |
|---|---|---|
| Specific gravity (12% MC) | 0.53 | 0.60 |
| Side hardness, lbf (12% MC) | 880 | 1,320 |
| Modulus of rupture, lbf/in² (12% MC) | 11,000 | 15,400 |
| Modulus of elasticity, million lbf/in² (12% MC) | 1.19 | 1.74 |
| Compression perpendicular to grain, lbf/in² (12% MC) | 890 | 1,160 |
| Radial shrinkage, green to ovendry (%) | 4.8 | 4.9 |
| Tangential shrinkage, green to ovendry (%) | 8.9 | 7.8 |
| Volumetric shrinkage, green to ovendry (%) | 13.8 | 13.3 |
| Dimensional change coefficient, tangential (per 1% MC) | 0.00315 | 0.00274 |
| Dimensional change coefficient, radial (per 1% MC) | 0.00165 | 0.00169 |
| Green MC of heartwood (%) | 61 | 46 |
| Tangential/radial shrinkage ratio (calculated) | 1.9 | 1.6 |
| Heartwood decay resistance (Table 14-1) | Slightly or nonresistant | Slightly or nonresistant |
Seasonal Movement and Shrinkage Behavior
In an epoxy river table, wood movement exerts stress along the epoxy-wood bondline. Differences in tangential and radial shrinkage rates define how prone a board is to cupping, warping, or stressing joints when room humidity changes.
Total shrinkage from green to ovendry reveals notable differences:
- Hackberry: 4.8% radial, 8.9% tangential, and 13.8% volumetric shrinkage, producing a tangential/radial (T/R) ratio of 1.9.
- White Ash: 4.9% radial, 7.8% tangential, and 13.3% volumetric shrinkage, producing a calculated T/R ratio of 1.6.
Hackberry’s higher tangential shrinkage and higher T/R ratio mean flat-sawn slabs will experience greater seasonal width fluctuations across the grain and an increased tendency to cup under humidity swings. This is reinforced by the dimensional change coefficients per 1% change in moisture content below the fiber saturation point: Hackberry’s tangential coefficient is 0.00315 compared to 0.00274 for White ash, while radial coefficients are virtually identical (0.00165 for Hackberry versus 0.00169 for White ash).
When acquiring green lumber, initial drying demands also differ. Hackberry averages a green moisture content of 61% in heartwood and 65% in sapwood, whereas White ash starts significantly drier at 46% green heartwood moisture and 44% in sapwood.
Heartwood Decay Resistance
According to Table 14-1 of the USDA Wood Handbook, both Hackberry and White ash heartwood are categorized as “Slightly or nonresistant” to decay. Neither species should be used for permanent outdoor furniture exposed to rain and soil contact. For indoor tables, always follow your epoxy manufacturer’s technical data sheet regarding surface preparation, sealing coats, and finish protection.
Which to Pick When
Choose White Ash when:
- You need maximum dent resistance for high-abuse surfaces such as busy family dining tables or commercial desks.
- Your design features long unsupported spans or extended overhangs where high stiffness (MOE of 1.74 million lbf/in²) prevents noticeable sag.
- You want lower tangential movement (0.00274 per 1% MC) and a lower T/R ratio (1.6) to reduce seasonal stress on wide epoxy pours.
Choose Hackberry when:
- You want a lighter finished slab (specific gravity of 0.53 vs. 0.60) that is easier to handle and move.
- The tabletop design incorporates adequate mechanical base support, mitigating the impact of its lower bending stiffness.
- You prefer the distinctive grain patterns of hackberry and can keep room relative humidity reasonably consistent year-round.
Sources
Published October 28, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: When inspecting dried slabs for hairline cracks along the grain, note that White ash increases significantly in tension perpendicular to grain from 590 lbf/in² green to 940 lbf/in² at 12% moisture content, whereas Hackberry drops slightly from 630 lbf/in² green to 580 lbf/in² at 12%, making dry Hackberry comparatively more sensitive to cross-grain tensile splitting during aggressive processing. (Source: USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-282, 2021).)