Timber

• Timber varies in bending strength from about one twenty-third of mild steel , according to the species & to the presence or absence of knots & faults in the timber . 
•  Its stiffness is low but in relation to its own weight which is quite light m it is relativekly very stiff . 
• It has a relatively high strength / weight ratio & is suitable for lightly or modera;ltely loaded low - rise building frames . 
• Timber is a combustible material . it easily burns in the form of thin boards . it burns less readily when its thicknesses is greater than 150mm 
• The application of fire retardants may reduced the combustibility of the timber . 
• Timber is also susceptible to attacks by wood boring insects . For structural use , most timber requires treatment . 

properties of timber

• Strength varies according to : 

- the species 

- the presence of knots . 

• low stiffness 
• high strength to weight ratio 
• combustible : burn easily 
• used for " 

- moderately loaded low rise building frames 

- single storey buildings .