E CHNI AL NO JTE NUMBER F-3 3
PRODUCTS lkORA ORY UNITED STATES FOREST SERVICE
. WISCONSIN RC$ REVISED OCTOBER. 1931
IPARATIVE DURABILITY OF GREEN AND SEASONED TIMBER
Experiments conducted by the Forest Products Labotory have failed to show any practical difference in the urability of untreated green and untreated seasoned timber* when exposed to weather in contact with the ground.
The following results were obtained in an experint with railway ties in cooperation with the Northern itfic Railway.
Green and Seasoned Ties (Untreated)
Place Species Average Life
wood, Wash. Douglas fir, green 7.7
Douglas fir, seasoned 7.8
Plins Mont. Douglas fir, green 7.6
Douglas fir, seasoned 7.7
Western larch, green 7.3
Western larch, seasoned 7.4
In each of these cases the average life of seasoned ties was only one-tenth of a year longer than that of the green ties. This difference is obviously so slight as to be negligible. Intwo experiments under observation by the Forest Products Laboratory in which both seasoned and unseasoned untreated posts are being used under comparative conditions, the seasoned posts are giving better results in one case and the u seasoned4n the other case.
In service data being obtain.d on sever&1~grgups of poles, the rate of depay/ in the -geen Voles is a little less than in the seasof.pe poles.
The fact that green and seasoned timb-ers have similar durability when used in exposed places may be explained as follows: Moisture content is an important factor in the rate at which a stick of timber decays.
As soon as the timber is placed it begins to take up or give off moisture, according to its condition of seasoning and the conditions of exposure. Within a
relatively short time in exposed construction both green and seasoned timbers reach the same moisture content.
When used in buildings, however, wood often does not dry out rapidly after being placed. Wood for interior construction must be seasoned before used; otherwise, it is likely not only to shrink to a serious extent but also to decay before it seasons. Very expensive building repairs have been necessitated by the
use of green lumber, UNIVERSITY OF FLORIDA
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