Diania Timber Overview for Epoxy River Tables
Diania represents timber from several African hardwood species within the genus Celtis, specifically Celtis adolfi-friderici, Celtis tessmannii, Celtis brieyi, and related Celtis p.p. According to the CIRAD Tropix technical sheet, Diania and Ohia are two distinct groups of Celtis species that are sometimes marketed collectively under the commercial trade name African Celtis. For woodworkers sourcing material for epoxy river tables or custom tabletops, Diania offers a distinctive aesthetic, but its physical properties demand strict adherence to moisture management and proper workshop tooling.
Appearance, Color, and Slab Potential
The heartwood of Diania displays a light yellow to yellowish-white tone, occasionally marked by greenish veins or greenish discoloration in the innermost zones of the log. Its sapwood is not clearly demarcated from the heartwood. The wood features a medium texture with grain that runs straight or slightly interlocked. Diania logs typically measure from 70 to 90 cm in diameter, providing solid widths for mid-sized single-slab tops or paired bookmatched slabs along a central epoxy river pour.
Density, Monnin Hardness, and Structural Strength
Diania is a moderately dense hardwood with an average specific gravity of 0.72 at 12% moisture content. In working terms, this equals a density of about 44.9 lb/ft³, meaning a 2-inch-thick slab weighs approximately 7.5 lb per square foot. Mechanical testing published by CIRAD lists its crushing strength at 59 MPa (about 8,560 psi), static bending strength at 111 MPa (about 16,100 psi), and modulus of elasticity at 16,200 MPa (about 2,350,000 psi).
The wood carries a Monnin hardness value of 5.0. The Monnin system is a standardized French timber hardness test where higher numeric values represent harder wood surfaces. It operates on an entirely different scale and testing methodology than the Janka hardness test, and Monnin figures must never be converted or equated to Janka ratings. At 5.0 on the Monnin scale, Diania exhibits ample surface resistance against denting for high-use furniture surfaces like dining and conference tables.
Dimensional Stability and Epoxy Bondlines
Understanding wood movement is vital when pairing Diania with rigid epoxy resins. CIRAD reports a total tangential shrinkage of 7.4% and a total radial shrinkage of 4.0% from green to oven-dry, resulting in a tangential-to-radial shrinkage ratio (St/Sr) of 1.9. The fibre saturation point is 26%, with a coefficient of volumetric shrinkage of 0.45% per 1% change in moisture content.
An St/Sr ratio of 1.9 indicates a moderate differential between tangential and radial movement, which introduces a moderate tendency toward cupping if moisture shifts occur across the slab. Because epoxy does not expand or contract with humidity changes, any significant dimensional movement in Diania will place stress along the resin bondline. Slabs must be fully dried to stable interior moisture equilibrium and thoroughly sealed across all faces, edges, and underside surfaces to prevent interfacial shearing.
Drying Risks and Natural Durability
Diania has a slow drying rate and carries a high risk of distortion as well as a high risk of checking. CIRAD notes that drying defects can be mitigated by top-weighting lumber piles and applying end-coating sealers to the log ends or slab ends. The suggested kiln drying schedule operates between 53 and 65 °C (about 127 to 149 °F). The wood is also very prone to blue stain fungal discoloration during storage or slow air drying.
In terms of natural resistance, Diania heartwood is classified as Durability class 5 (not durable) against wood-decay fungi, and it is Class S (susceptible) to termites and dry-wood borers across the entire cross-section. It is rated for Class 1 interior use only (dry environments without dampness). However, its heartwood treatability is Class 1 (easily permeable), meaning it readily absorbs protective chemical treatments or stabilizing sealers.
Tooling and Assembly
Machining Diania exerts a fairly high blunting effect on cutter edges. Sawing requires stellite-tipped saw teeth, and surfacing operations call for tungsten carbide tooling. Celtis tessmannii can occasionally present a high silica content, further accelerating edge wear. Where slight interlocked grain is present, careful feed rates are needed to avoid tearout. For table bases and joinery, screwing and nailing hold well, but pre-boring is strictly necessary because the timber tends to split when fasteners are driven without pilot holes.
| Property | CIRAD Tropix value | What it means / US units |
|---|---|---|
| Botanical name(s) | Celtis adolfi-friderici, Celtis tessmannii, Celtis brieyi (synonymous), Celtis p.p. | |
| Colour / texture / grain | Light yellow; texture medium; grain straight or interlocked; interlocked grain slight | |
| Specific gravity (12% MC) | 0.72 | about 44.9 lb/ft³; a 2-inch-thick slab weighs about 7.5 lb per sq ft |
| Monnin hardness (12% MC) | 5.0 | French hardness scale; higher = harder (not a Janka value) |
| Total tangential shrinkage | 7.4 % | green to oven-dry |
| Total radial shrinkage | 4.0 % | green to oven-dry |
| Ratio St/Sr | 1.9 | closer to 1 = less cupping tendency |
| Coefficient of volumetric shrinkage | 0.45 % per % MC | volume change per 1% change in moisture content |
| Fibre saturation point | 26 % | |
| Thermal conductivity | 0.24 W/(m·K) | |
| Crushing strength (12% MC) | 59 MPa | about 8,560 psi |
| Static bending strength (12% MC) | 111 MPa | about 16,100 psi |
| Modulus of elasticity (12% MC) | 16,200 MPa | about 2,350,000 psi |
| Decay (fungi) resistance | Durability class 5 – not durable | |
| Termite resistance | Class S – susceptible | |
| Dry-wood borer resistance | Class S – susceptible (risk in all the wood) | |
| Heartwood treatability | Class 1 – easily permeable | |
| Use class from natural durability | Class 1 – inside (no dampness) | |
| Drying | rate slow; distortion: high risk; checking: high risk; collapse: no known specific risk; casehardening: no known specific risk | |
| Suggested kiln program temperatures | 53–65 °C | about 127–149 °F |
| Machining | blunting fairly high; saw teeth: stellite-tipped; cutting tools: tungsten carbide | |
| Nailing and screwing | Good but pre-boring necessary | |
| CITES status | This species is not listed in the CITES Appendices (Washington Convention 2025). Notes. Diania and Ohia are two different groups of Celtis species. Sometimes they are grouped together under the name of African Celtis. |
Values from the CIRAD Tropix technical sheet (average values for mature wood, 12% moisture content where noted). US-unit conversions are calculated by BigEpoxy (1 MPa = 145.04 psi; density = specific gravity × 62.43 lb/ft³).
Frequently Asked Questions
What are the primary end-uses for Diania timber?
Beyond furniture and furniture components, CIRAD lists Diania for flooring, indoor staircases, interior joinery, interior panelling, moulding, turned goods, heavy carpentry, vehicle or container flooring, formwork, boxes and crates, matches, sliced veneer, and face or core veneer for plywood.
Is Diania protected under CITES export controls?
No. Diania is not listed in the CITES Appendices under the Washington Convention (2025 update), meaning international trade in this timber is not subject to CITES restrictions.
Can Diania slabs be used for outdoor epoxy tables?
No. The natural durability of Diania heartwood is Durability class 5 (not durable), and it is classified under Class 1 use (interior applications with no dampness). It is susceptible to fungal decay, dry-wood borers, and termites, making it unsuitable for exterior conditions.
How wide of a live-edge slab can be sourced from Diania logs?
CIRAD reports typical Diania log diameters ranging from 70 to 90 cm. Slabs cut from these logs generally provide usable widths within that range, suitable for medium-width live-edge dining tables or two-piece river configurations.
Why is pre-boring required when mounting table bases to Diania?
Diania wood tends to split when fasteners are inserted. While nail and screw holding strength is rated as good once installed, pre-boring pilot holes is necessary to prevent splitting around table-mounting hardware.
Does Diania require specialized tooling in the wood shop?
Yes. Due to a fairly high blunting effect and occasional high silica content in species such as Celtis tessmannii, stellite-tipped blades and tungsten carbide cutters are recommended to maintain clean cuts and avoid surface burn.
Sources
Published October 31, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: The CIRAD Tropix sheet notes that Diania emits a particularly unpleasant odour when green or rewetted, reinforcing the need for thorough, slow drying and a complete moisture seal before installing it in an indoor tabletop. (Source: CIRAD Tropix 7 technical sheet: Diania.)