Wood Rot part 2-- Unicoi Ludd

Wood Rot Part 2. 

In part 1 you learned that the best, easiest & cheapest way to preserve wood is to keep it dry so that decay causing organisms cannot survive. Very useful information for rafters, joists and other off grade applications but what about ground contact like fence posts ? For the purposes of this discussion, we will assume that we are not living in an extremely dry or consistently cold environment. Since fence posts are in direct contact with the ground, the difficulty of preventing decay is tremendous. We have probably all seen fence posts held up by the fencing rather than the other way around. The reason fence posts rot at the base is simple- that "hot zone" of moisture, fungi & microbial life that we call top soil. The top 6 inches of soil are the hardest place to prevent decay. You may have experienced a post rotted thru at the base, but the top part perfectly fine & the end deepest in the ground still good. In the case of ground contact, keeping the wood dry is generally not practical. One question that is commonly asked is "can't I paint it"? The answer is - yes you can, but it won't do any good. Barrier methods of protecting wood, like paint, depend on the coating film being 100% intact. Their primary job is to repel water before it can be absorbed by the wood and permit decay organisms to live. Wood, in its ceaseless effort to match the environment swells & shrinks as it gains or losses moisture. Paints (and other coatings) have some flexibility to cope with that but all will eventually fail. Once the coating has failed moisture will be absorbed by the wood and the ever present fungi etc. will go to work. At this point the paint works against you because now it is acting like the bark of the tree and holding the moisture in. This is why you should re-paint your house regularly- to renew the protective film. So unless you're going to pull up your fence posts and repaint them frequently, don't plan on paints or urethanes to preserve fence posts. In post # 3 we will discuss chemical treatments that deter the decay causing organisms.