Properties and Uses

Gerutu

The Standard Malaysian Name for the timber of the heavier species of Parashorea. (Dipterocarpaceae). The trees are usually large, with large buttresses and tall, clear bole to a good height. Parashorea occurs in the lowland and hill dipterocarp forests. The species of P. densiflora and P. stellata are found in the southern and northern halves of the Peninsular respectively, whereas the species of P. globosa is very rare and known to exist only in Perak. Generally, the trees favour undulating, hilly jungles or valleys up to an altitude of about 600 m. The timber is a light hardwood with a density of 640–880 kg m^–3air dry. The sapwood is whitish yellow and is moderately distinct from the heartwood, which is light golden brown and darkens to a deep brown on exposure. Texture is moderately coarse and even, with interlocked grain. The timber is only moderately strong (Strength group C). It is slightly difficult to saw but is fairly easy to cross-cut. Planing, boring and turning are easy and the planed surface is smooth. The nailing property is rated as excellent. The timber seasons slowly with moderate end-checking and surface-checking and staining as the main sources of degrade. There are also slight splitting and insect attacks during drying. 13 mm boards take 4 months to air dry, while 38 mm boards take about 6 months. Shrinkage is high, with radial shrinkage averaging 1.8% and tangential shrinkage averaging 3.5%. The movement in seasoned timber is classified under Type IV (based on the species Parashorea densiflora). For kiln-drying, Schedule C is recommended. 25 mm boards take approximately 14 days to kiln-dry from 50 to 10% moisture content. The timber is very prone to surface-checking and also warping, especially in thick sections and when stacking is poor. It is recommended that this timber be air-dried under cover to 30% moisture content before kiln-drying to reduce the kilning time. A four hours high humidity treatment may sometimes be required to reduce case hardening. Schedule C is applicable to drying materials of up to 40 mm in thickness. However, for drying stocks of 40 mm to 75 mm, the relative humidity should be 5 percent higher. For timbers thicker than 75 mm, the relative humidity should be 10% higher. The timber is non-durable and is rather difficult to treat with preservatives.

USES: The timber is suitable for light to medium construction under cover, panelling and partitioning, utility furniture manufacture, strip flooring, veneer for plywood manufacture, pallets, boxes and crates.

Vernacular names applied include gerutu (P.M.) with various epithets, heavy white seraya (Sab.), meranti gerutu (P.M.) and other localised names which are too numerous to be listed here. Major species include P. densiflora, P. globbosa and P. stellata from Peninsular Malaysia, and P. parvifolia and P. smythiesii from Sabah and Sarawak.