This is a direct result of using the petroleum oil paint
or acrylic paint. These modern types of paint will trap
the moisture in the wood and rot the wood from the inside.
It is interesting to realize that this type of deck designs
have been around for 100’s of years but it appear
that there was no major problems until the petroleum paint
was started to be used. This type of damage is directly
linked to the type of paint. It has nothing to do with the
quality of the wood. If purified linseed oil paint had been
used, this porch would have been in perfect condition today.
American Four Square Front Porch Project.