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White fir haq a short life under conditions favorable to decay. The hqartwoods of southern yellow pine and Douglas fir are more decay-resistant than that of white fir, while the heartwood of the hemlocks and spruces may be considered as between that of white fir and Dougtas fir in decay resistance.

Sapwood of all species rots quickly under conditions that favor decay. However, it ig unifornly admitted in house construction. The low decay-resistance of white fir cannot therefore be considered a serious handicap to its use in the construction of small houses. This is shown by the fact that the framing, sheathing, subfloors, and siding of srqrng or many oro nouses suil standlng, or houses torn down because of obsolescence, contain a high percentage of sapwood or are old houses still down constructed of species haviing decay resistance no greater than that of white fir.

White fir is similar to a number of the lighter, softer, and weaker species used in construction. The desirable properties of such species are those that facilitate construction. Light weight facilitieJ handling, and softness makes for ease in cutting, sawing, and nailing. Of the woods commonly used in construction only northern while pine is lighter than white fir. White fir has the iame hardness as western yellow qine, is somewhat harder than eastern spruce and northern white pine, and is softer than the other species iommonly used. Table 4 compares the weight and the hardness of white fir with those of other species.

Table l.-Working stresses for common grades of dinrension 4 inches and under in thickness.

(Recommended by Forest Products Laboratory for material con- torming to American Lumber Standardst basic provisions for struc_ tural material used in continuously dry locations..t coqPres' cbmpres- Averagel species of wood ,,1:!;',"

_bending to grain shear 1o grain ticity t tmon AII grades Common Common All grades