Keruing wood: A Versatile Heavy Hardwood for Durable Construction
Keruing wood, known by its Standard Malaysian Name, refers to the wood of the genus Dipterocarpus spp. (Dipterocarpaceae). Commonly found in Peninsular Malaysia, Sabah, and Sarawak, it is recognized by various vernacular names such as keruing, seraya batu, and red seraya. The species include D. elongatus, D. baudii, D. chartaceus, D. confertus, D. concavus, D. cornutus, D. costatus, D. crinitus, D. dyeri, D. gracilis, D. grandiflorus, D. kerrii, D. kunstleri, D. lowii, D. obtusifolius, D. rotundifolius, D. sublamellatus, and D. verrucosus. The sapwood is lighter, usually greyish, while the heartwood ranges from red-brown to purple-red, darkening upon exposure.
## Density
Keruing is classified as a Medium Hardwood with a density ranging from 690-945 kg/m³ (air dry) in Peninsular Malaysia, and 595-865 kg/m³ (air dry) in Sabah.
## Natural Durability
The durability of Keruing varies by species, from moderately durable to non-durable in tropical conditions. The heartwood is resistant to fungal attacks but not to termites, while the sapwood is prone to drywood termite attacks. It is generally classified as not durable, with an average service life of less than two years in untreated conditions.
## Preservative Treatment
Keruing wood is highly receptive to preservative treatments, enhancing its durability and longevity.
## Texture
Keruing has a moderately coarse to coarse texture, with straight to deeply interlocked grain.
## Strength Properties
Keruing falls into Strength Group B (SG 5), indicating it is a strong wood suitable for various structural applications.
## Machining Properties
Keruing is relatively easy to work with. Planing ranges from easy to slightly difficult, and the finish is generally smooth.
## Air Drying
Keruing seasons well, with some species experiencing end-splitting and surface-checking. The air drying time varies by species, with some drying faster than others.
## Kiln-Drying
Kiln Schedule D is recommended for Keruing. The drying process must be carefully monitored to prevent end-splitting and surface-checking.
## Shrinkage
Keruing exhibits high to very high shrinkage rates from green to air-dry conditions.
## Movement in Service
Keruing’s movement in service varies by species, classified under Type IV and Type V, indicating moderate to high movement.
## Uses
Keruing is ideal for heavy construction, including posts, beams, joists, rafters, ship and boat building, vehicle bodies, container flooring, and, when treated, railway sleepers, harbor works, bridges, power-line poles, and telegraph poles.
