'TECHNICALNOTE number F-33 
 
 FOREST PRODUCTS LABORATORY UNITED STATES FOREST SERVICE 
 
 MADISON. WISCONSIN ^H REVISED OCTOBER, 1931 
 
 COMPARATIVE DURABILITY OF GREEN AND SEASONED TIMBER 
 
 Experiments conducted by the Forest Products Labo- 
 ratory have failed to show any practical difference in the 
 durability of untreated green and untreated seasoned tim- 
 bers when exposed to weather in contact with the ground. 
 
 The following results were obtained in an experi- 
 ment with railway ties in cooperation with the Northern 
 Pacific Railway, 
 
 Green and Seasoned Ties (Untreated) 
 
 Place Species Average Life 
 
 in Years 
 Maywood, Wash. Douglas fir, green 7.7 
 
 Douglas fir, seasoned 7.8 
 Plains, 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 tc 
 be negligible . Intwo experiments under observation by the 
 Forest Products Laboratory in which both seasoned and 
 unseasoned untreated posts are being used under compara- 
 tive conditions, the seasoned posts are giving better 
 reiiults in one case and the unseasoned 3 other case. 
 
 In service data being obtained on several; grpups 
 of poles, the rate of de£ay/ in - the ^r.een poles is a 
 little less than in the seaso! 
 
The fact that green and seasoned timbers 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 in- 
 terior construction must be seasoned before used; other- 
 wise, it is likely not only to shrink to a serious 
 extent but also to decay before it seasons. Very ex- 
 pensive building repairs have been necessitated by the 
 use of green lumber. ilMIVCDeiT 
 
 HllllllllillM ^ OF FL0R| DA 
 
 3 1262 09216 7187 
 
 
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 LV. 72997 F