Mention was made that Douglas-Fir has poor penetration of preservatives. What can be done to increase the penetration of preservative treatments in the wood?

Douglas-Fir, along with other refractory species such as Hem-Fir and Spruce-Pine-Fir, are commonly incised in order to allow for additional penetration of the treatment into the wood. Southern Pine, Red Pine, and Ponderosa Pine are exceptions in that they readily accepts treatment chemicals and do not require incising when undergoing preservative treatments.

The following FAQ is based on the presentation of DES140 – Structural Condition Assessment of in-Service Wood.