Unpainted wood.


Denny Anspach <danspach@...>
 

It has been hard for me to know yet just how to respond to Mike
Brock's relating his experience of having a perfectly good creosoted
post rotted away when put into the ground at his house (:-)). I too
have had the same experience.

Rot will not occur in the ideal environs of wood of 30-35% moisture
content. It will not occur, or be arrested in the wettest of environs,
or if the wood moisture content is <20% . It will not occur in
environs >105º nor <40º. It will not occur, or be severely inhibited
in low oxygen conditions.

How wood generally will likely last or react in any given adverse
environment has more variables than Carter has pills, and a full
treatment requires a book. Suffice it to say that the 4500 years-old
wood Solar boat was found completely intact in the super dry environs
of the Great Pyramid of Cheops , while 1000-1200 year old intact
Viking ships have been found completely intact buried deep in the
wettest of mud at Gokstad in Norway and Roskilde in Denmark.

In the most general way, wood is painted primarily for aesthetic
reasons, and secondarily only slightly less for protection from the
elements- primarily the sun. Water seeps into wood primarily (not
exclusively) from the end grain, and if the end grain is protected,
unpainted wood can exist in pretty unfriendly environments for many,
many years. But then, even if the end grain is not protected, some
woods can survive well unpainted anyway- if they are of species
variably resistant to dry rot fungi- redwood, teak, old growth
American Mahogany, Port Orford cedar, old-growth Douglas fir, and a
wide variety of old growth cedars .

The undersides of freight cars were not painted for the same reasons
that we do not optionally paint the undersides of houses without
basements, the undersides of piers and docks (if we even paint the
topsides at all!), paint wood shingles, and often do not paint house
or barn siding (I personally have done both- house roofs and siding on
the former, and a large barn in the latter)! It is not necessary,
except for esthetics, providing that the proper wood has been chosen
and installed for the particular environment.

As to the rotted creosoted post. Quite often "creosoted" posts were
not immersed or pressure treated so that the fluid could leach deep
into the end grain where it could do some good. In either way,
however, with time, all fungicides (creosote included) eventually
leach away, allowing the inherent rotting process to do its dirty
work. For about 25 years, when I have buried posts in the yard, I
seal end grains with epoxy- which very effectively significantly prolongs the life of the post .

I have a feeling that most freight car decking was old growth Douglas
fir, and flat car decking either of the same, or white oak- both woods
that wear well, and are also relatively pretty dry rot resistant
unless poorly installed.

Denny







Denny S. Anspach MD
Sacramento

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