MALAYSIAN TIMBER - Physical Properties

With over 58 per cent of its land area under natural forest, Malaysia is home to over 2,650 species, many of which are of commercial importance. Malaysia's location in the tropics means that its trees have 365 growing days in a year. This allows the trees ample time to grow and develop without seasonal interruptions.

Apart from its intrinsic beauty, wood is highly versatile, has good insulation properties and is strong yet easy to use. Malaysia has an endless selection of timbers from which to choose. Malaysian timbers have been utilised in various applications, including interior designs. The multitude of colours available represents an artist’s palette, enabling an endless expression of creativity.

The versatility of wood is demonstrated by a wide variety of products. This variety is a result of a spectrum of desirable physical characteristics or properties among the many species of wood. In many cases, more than one property of wood is important to the end product. For example, to select a wood species for a product, the value of appearance-type properties, such as texture, grain pattern, or color, may be evaluated against the influence of characteristics such as machinability, dimensional stability, or decay resistance.

Wood exchanges moisture with air; the amount and direction of the exchange (gain or loss) depend on the relative humidity and temperature of the air and the current amount of water in the wood. This moisture relationship has an important influence on wood properties and performance. This chapter discusses the physical properties of most interest in the design of wood products.

Some physical properties discussed and tabulated are influenced by species as well as variables like moisture content; other properties tend to be independent of species. The thoroughness of sampling and the degree of variability influence the confidence with which species-dependent properties are known. In this chapter, an effort is made to indicate either the general or specific nature of the properties tabulated.

Physical Properties

Name Botanical Name
Air-Dry Density Kg/m3
Shrinkage
Rec Kiln Schedule
Radial %
Tangential %
HEAVY HARDWOOD
Balau Shorea spp.
850-1,155
1.7-2.1
3.5-3.9
B
Bitis Madhuca utilis, palaquium ridleyi & P. Stellatum
820-1,200
2.8
4.0
n.a.
Chengal Neobalanocarpus heimii
915-980
1.1
2.6
B
Giam Hopea spp.
865-1,220
2.6-4.4
1.4-2.0
B
Red Balau Shorea spp.
800-880
1.4-2.2
3.2-3.6
G
Merbau Intsia palembanica
515-1,040
0.9
1.6
n.a.
Tembusu Fagraea spp.
640-1,075
1.1
1.6
n.a.
Resak Vatica spp.
655-1,155
1.5
3.4
B
Keranji Dialium spp.
755-1,250
1.0-2.3
1.7-3.7
E
Kekatong Cynometra spp.
880-1,155
1.6
2.7
B
MEDIUM HARDWOOD
Kulim Scorodocarpus borneensis
640-795
1.7
3.2
n.a.
Keruing Dipterocarpus spp.
690-945
1.6-3.1
3.3-7.4
D
Kempas Koompassia malaccensis
770-1,120
2.0
3.0
E
Mengkulang Heritiera spp.
625-895
1.3-1.7
3.0-3.8
D
Merpauh Swintonia spp.
640-880
0.8-1.4
1.5-2.0
C
Meransi Carallia spp.
670-930
0.6
1.3-2.3
n.a.
Mata Ulat Kokoona spp.
895-1,055
1.6-2.6
2.0-3.0
C
Rengas Gluta spp.
640-960
1.0
1.8
E
Punah Tetramerista glabra
625-800
3.2
4.5
C
Tualang Koompassia excelsa
800-865
1.5
1.7
E
Simpoh Dillenia spp.
675-815
2.2
3.9
C
Kasai Pometia spp.
735-915
2.8
3.5
D
Kelat Eugenia spp.
495-1,010
1.9
3.3
C
Keledang Artocarpus spp.
495-945
0.8-1.0
1.7-2.6
F
Kapur Dryobalanops spp.
575-815
1.5-2.1
3.8-5.1
E
Merawan Hopea spp.
495-980
0.9-1.3
2.2-3.3
H
LIGHT HARDWOOD
Melantai Shorea macroptera
415-625
0.8-0.9
2.6-2.8
H
Kungkur Pithecellobium spp.
465-850
0.6
0.9
n.a.
KembangSemangkuk Scaphium spp.
515-755
1.2
3.0
H
Medang Spp. of Lauraceae
350-880
0.9-2.0
2.2-3.9
n.a.
Melunak Pentace spp.
530-755
1.4
2.5
n.a.
Kedondong Spp. of Burseraceae
495-975
1.8-2.4
3.2-4.1
J
Jelutong Dyera spp. 
415-495
0.8
2.0
H
Machang Mangifera spp.
545-640
0.9-1.3
1.7-1.9
F
Ramin Gonystylus spp.
530-785
1.6-1.9
3.4-4.0
C
Dark Red Meranti Shorea spp.
560-865
1.1-2.1
2.9-4.4
F
Mempisang Spp. of Annonaceae
370-960
1.5-4.0
2.7-4.5
H
Meranti Bakau Shorea uliginosa
595-755
1.0
2.7
H
Rubberwood Hevea brasiliensis
560-640
0.8
1.2
E
White Meranti Shorea spp.
495-915
0.6-1.8
1.4-3.0
J
Nyatoh Spp. of Sapotaceae
400-1,075
1-3
1.9-4.3
E
Mersawa Anisoptera spp.
515-735
1.4
3.2-3.8
E
Light Red Meranti Shorea spp.
385-755
1.5-2.6
3.8-7.4
F
Sepetir Sindora spp.
530-785
1.5
2.9
G
Gerutu Parashorea spp.
640-770
1.6-2.0
3.3-3.6
C
Pulai Alstonia spp.
370-495
2.3
2.8
J
Yellow Meranti Shorea spp.
575-735
0.9-1.2
3.1-3.8
J
Petai Parkia spp.
415-815
0.8-1.3
1.8-2.0
n.a.
Geronggang Cratoxylum spp.
350-610
2.2
4.2
E
Durian Durio spp., Neesia spp.
420-800
1.3-2.4
1.6-4.0
n.a.
Bintangor Calophyllum spp.
465-865
1.4-2.1
2.0-3.7
C
Sesendok Endospermum spp.
305-655
1.2
1.3
J
Terap Artocarpus spp.
400-560
1.5-2.0
2.9-4.4
n.a.
Penarahan Spp. of Myristicaceae
370-770
2.1-2.2
3.1-3.2
n.a.
Perupok Lophopetalum spp.
480-640
2.3-2.4
2.7-3.0
n.a.
Terentang Campnosperma spp.
320-560
1.6-2.1
3.2-5.5
n.a.
SOFTWOOD (Conifers)
Damar Minyak Agathis borneensis
385-580
1.2
2.5
D
Podo Podocarpus spp.
415-735
n.a.
n.a.
n.a.

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Moisture movement and shrinkage

 

As wood dries below its fibre-saturation point, it shrinks. However, the loss in dimension is not the same in all directions. Timber shrinks in three directions:

  • Longitudinally, along the grain of the timber
  • Radially, across the growth rings and
  • Tangentially, along the line of the growth rings.

The longitudinal shrinkage is small at about 1%. While discounted in milling processes, it can be an important consideration in construction with unseasoned timber. In the radial direction, depending on the species, shrinkage is around 3% to 6% when drying down from fibre saturation point (about 25 – 30% moisture) to 12% moisture content. In the tangential direction, the shrinkage is generally about twice this amount, 6% to 12% over the same moisture range.

These differential rates of shrinkage have considerable effect on methods of milling and the performance of timber in service, especially when unseasoned timber is used and allowed to dry in service. Considerable deformation can occurs. The effect of shrinkage on timber sections cut from various sections of a log is shown in Figure 1.

If seasoned timber is used, the direction of cut is usually not as important as subsequent changes in dimension, or ‘movement’, are related to changes in the piece’s equilibrium moisture content due to environmental changes.

 

 

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Note:

CLASSIFICATION

Malayasian timber are classified into four categories viz., Heavy Hardwoods (HHW), Medium Hardwood(MHW), Light Hardwoods(LHW), and Softwoods, is based on the normal botanical convevtion. The classification of the three categories of Hardwoods is based largely on the average density of the timber at 15% moisture content. The exception to this rule is for the Heavy Hardwood category which emplaces priority on natural durability over density. As an example, Merbau, which has the characteristic of the hardwood being naturally durable and having average air-dry density of 800kg/m3, is classifide as a HHW. on the other hand, Kempus, having a higher average density of 890kg/m3, is classifide as a MHW as the heartwood is found to be not durable. The distinction between Medium and Light Hardwood is based solely on average density. The classification system is summarised in the Table below.

CLASSIFICATION TABLE
Classification
Density Range(15% m.c.)
Heavy Hardwood
800-1120kg/m3
Medium Hardwood
720-880kg/m3
Light Hardwood
400-720kg/m3
Softwood (Botanical Distinction)

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SEASONING and SHRINKAGE

Seasoning characteristics are based on test results using test boards placed on 25 mm stickers. The test boards were stacked in open-sided sheds and were protected from rain and direct sunlight. Shrinkage data are given for both the radial and the tangential directions. The data expressed In percentage of the width In the green condition, are based on measurements from the green to the air-dry condition (15% m.c.). One of the ten kindling schedules shown in Appendix I is recommended for each timber. The schedules are suitable for application On timbers up to 40 mm thick. For thicknesses exceeding 40 mm but less than 75 mm, the relative humidity should be 5% higher, and for thicknesses exceeding 75 mm, the relative humidity should be 10% higher.