Dry rot is a living organism related to fungi. I believe
the term dry rot started because wood
submerged underwater does not develop this type of rot, and only wood exposed above water rots thus the term "dry rot".
When I was a young apprentice many of the old shipwrights thought that only rain water caused dry rot.
As dry docked boats, or boats sitting outside out of water on stands or trailers, got substantial amounts rain water
in them when left unattended and these boats developed more and faster growth rot, so it is easy to see where
this folk myth came from.
The most common forms of rot found on a boat are brown rot and white rot. Brown rot exhibits a rectangular
or cubicle fracturing on the wood and in some cases where the wood has substantially blackend it often looks like burned lumber.
White rot decays the wood leaving a fibrous appearance and lightens in color.
Both forms of rots need a moisture content of 20% and higher but below complete saturation. Both
forms of rot require air to grow. Therefore, dry rot can be prevented by keeping the wood dry and/or sealed from
Another factor determining the speed that dry rot grows is the ambient substrate temperature. Dry rot
turns off when it is below 32 degrees farenheit and above 110 degrees farenheit with optimal grow occuring between 50 and