Do all species of wood require preservative treatment?
The heartwood of some species has a relatively high degree of natural resistance (Table 1.) These woods might be used satisfactorily in some application without treatment. The sapwood of all species is highly susceptible to decay and insect attack in certain conditions of moisture content, temperature, etc. It is important to recognize that untreated woods with a high degree of natural resistance to deterioration do not equal the life expectancy of treated pine, for example. It is hard to place a figure on life expectancy; however, some treaters mention a guarantee of 20 to 30 years. It would not be realistic to expect much more than 15 years of life from any of the untreated (high natural resistance) woods and in many instances less than this when they are used in exposed situations or in contact with the soil.
