What is the life expectancy of wood that was used in an attic truss? Does fire retardant change the life expectancy?

There are many factors that affect the strength (which in turn affects the life expectancy) of wood. The strength of wood depends heavily on the direction of the loads with respect to the grain. The moisture content (MC) of the wood also will have an impact on the strength. All other things being equal, the drier the wood, the stronger it will be. Changes in strength properties occur between 0-30% MC. The MC is dependent on relative humidity and temperature. If your attic is well ventilated, this should not be a factor. As far as the direct affect of temperature, strength properties of wood generally decrease when temperatures increase and increase when temperatures decrease (inverse relationship). At temperatures greater than 200 degrees Fahrenheit strength loss is irreversible. Normally, this also will not be a factor in an attic. Even though chemical solutions reduce wood's strength, chemicals are used as preservative and fire-retardant treatments (FRT). The reduced capacity of ...