Handling & safety. Non-toxic. The acetylation process uses acetic anhydride (vinegar-related chemistry). No additional health risks beyond standard wood dust.
Properties
| Base species | Pinus radiata (acetylated) |
|---|---|
| Species type | Softwood |
| Origin | Manufactured in Arnhem, Netherlands (by Accsys Technologies). Source timber: sustainably certified Radiata Pine from New Zealand |
| Density | 510 kg/m³ |
| Janka hardness | 3,200 N |
| Modulus of rupture | 56 MPa |
| Elastic modulus | 8.8 GPa |
| Crushing strength | 42 MPa |
| Specific gravity | 0.51 |
| Porosity | Non-porous (softwood) |
| Movement class | Very low |
| Tangential shrinkage | 1.5% |
| Radial shrinkage | 0.7% |
| Volumetric shrinkage | 2.4% |
| T/R ratio | 2.1 |
| Durability (EN 350) | Class 1 |
| Relative cost | Budget |
Density and mechanical properties are typical values at around 12% moisture content. Shrinkage figures represent total dimensional change from fibre saturation to oven dry. Individual boards vary.
Description
Accoya moves very little compared with ordinary softwood, making it especially useful for exterior joinery, cladding, doors, windows, gates, garden structures, and painted outdoor projects where swelling, shrinking, twisting, and coating failure need to be kept to a minimum.
It machines well, takes paint and finishes reliably, and is one of the best timber choices where outdoor performance, low maintenance, and dimensional stability matter more than rustic visual character.
Anatomy
- Porosity: Non-porous
- Vessel Arrangement: Tracheids present; resin canals medium-large, very numerous and evenly distributed, mostly solitary.
- Vessel Description: N/A — softwood. No vessels; water conduction via tracheids.
- Parenchyma: Axial parenchyma in discontinuous uniseriate strands of 2–4 cells; sparse.
- Rays: Uniseriate; ray cells procumbent; typically 1–10 cells high.
Durability
- Durability Class: Class 1 — Very Durable
Class 1 durability — the highest rating, matching or exceeding teak, iroko, and European oak. Guaranteed for 50 years above ground, 25 years in ground contact. Indigestible to a wide range of insects and pests. Not detrimentally affected by salt water contact or immersion.
Odor
Slight vinegar-like scent (acetic acid) when freshly cut, which dissipates quickly.
Uses & Availability
Common Uses
Windows and door frames, external cladding, decking, garden furniture, gates, fascias, soffits, marine applications, bridge components, and any exterior joinery where long-term durability and dimensional stability are critical.
Pricing & Availability
Premium-priced — significantly more expensive than standard softwoods or even many hardwoods. Widely available in the UK through specialist timber merchants and joinery suppliers. Typically supplied in standard dimensions.
Conservation
- CITES Status: Unlisted
Lookalikes & Substitutes
Competes with naturally durable hardwoods like European oak, iroko, and teak for exterior joinery applications. Also competes with other modified woods (Kebony, ThermoWood) though Accoya’s Class 1 rating exceeds most alternatives.
Working the timber
Easy to work — comparable to a softwood or medium-density hardwood such as tulipwood. No special tools required for cross-cutting, ripping, planing, routing, and drilling. The modification process does not affect machinability as it is modified to the core. Glues well with standard PVA and polyurethane adhesives.
Finishing & gluing
Accoya’s acetylation makes it unusually dimensionally stable, so film finishes (paint/opaque systems) tend to last longer because the timber moves less under the coating. For clear exterior finishes, treat it like a very stable softwood: keep edge-sealing rigorous and avoid leaving end grain unsealed, as moisture cycling still drives greying and coating breakdown. If you notice a faint vinegar smell after machining, let the surface air off before coating and follow the finish manufacturer’s primer/sealer schedule.
Accoya generally bonds well with standard PVAs, aliphatic resins and PU glues, but its stability means joint fit matters more than “clamping it into place”—aim for accurate, close-fitting joints. Lightly abrade and de-dust before gluing, and avoid oily contamination from handling. For exterior joinery, prefer D4 PVA, resorcinol, PU or epoxy systems rated for wet service, and seal end grain to keep water out of the joint line.