Timber

• Unlike steel & concrete , timber is a natural product obtained from trees .
• Its strength varies according to its species & the presence or absence of knots & faults .
• The moisture content of timber  , measured as a percetage of its oven-dried weight is an important indication of its structural capacity & durability .

Structural Timber

• Timber is less prone to decay if its moisute content is below 25% & may be considered immune below 20%
• Timber is also susceptible to attacks by woods boring insects . For structural use , timber must be treated .
• Current codes of practice used in Malaysia for the design of structural timber are :
• MS 544 and BS 5268
• For structural use , most malaysian timber requires treatment but some ( e.g. chengal , balau , resak ) are naturally durable .
• Based on years of reasearch by Forest Research Institute Malaysia , Malaysian timber are classified into 4 strength groups L

1. A ( strongest ) : e.g. balau , chengal , kempas
2. B : Merbau , resak , keruing
3. C : Durian , meranti , nyatoh , ramin , rubberwood
4. D : (weakest) : damar minyak , jelutong .

• In small scale buildings with loadings such as those in house , timber frames are more than capable of supporting the load per meter run imposed by the roof & floor .
• The spans are small & therefore loads may be evenly distributed by single roof & floor construction on to the supporting floor beams & columns .
• Skeleton frames constructed in timber may be fabricated from solid timber sections , built-ip section or glued & laminated sections .
• For columns & beams , solid square or rectangular section are generally the most economical in cost .