Preservation of timber: Preservation of timber is done with the help of different types of preservatives to increases the life of the timer, make the timber structure durable, and protect it from the attack of fungi & insects 
Different types of preservatives: 
As-Cu Treatment: This is a special type of preservative which is developed at Forest research institute Dehradun. Which composition is as follows; 
1. As₂O₅.₂H₂O (Arsenic pentaoxide) 
2. CuSO₄.5H₂O (Copper sulfate) 
3. K₂Cr₂O₇ (Potassium dichromate) 
4. Na₂Cr₂O₇.2H₂O (Sodium dichromate) 
This preservative gives protection against the attack of White ants. 
Coal Tar: The process of heating the coal tar to make it workable condition is known as Tarring. Coal tar is Fire resistant. 
Creosote oil: Creosote oil is one of the best antiseptics. It is derived from wood or coal. It is harmless to wood and inflammable. 
Oil paints: The timber surface is coated with oil paints, it makes the timber durable.