Fifty years ago, most exterior siding and trim were vertical-
grain heartwood of western redcedar or redwood. All-heart-
wood vertical-grain grades of these species are still avail-
able as resawn bevel siding and lumber and are excellent
wood substrates for painting (Table 16–1). Other species are
generally available only as flat-grain or a mix of flat- and
vertical-grain lumber (for example, western hemlock, east-
ern white pine, lodgepole pine, eastern white cedar, radiata
pine, and southern yellow pine). Finishing characteristics of
flat-grain western redcedar and redwood are similar to other
low-density wood species having moderate EW–LW transi-
tion (such as eastern white pine, eastern white cedar, and
yellow poplar) Sawing to yield vertical grain is only practi-
cal with fairly large-diameter logs. Species available
in small-diameter logs yield mostly flat-grain lumber.
Other wood properties, such as knots, juvenile wood, and
extractives, affect wood finishing. Extractives include many
chemicals with different solubilities in water, organic sol-
vents, and paint resins (also called binders).
Manufacturing
The axial EW and LW cells in a log yield lumber of vari-
ous grain angles (Fig. 16–6). At one extreme (board a), the
growth rings are perpendicular to the plane of the board; at
the other extreme (board c), growth rings are parallel to the
plane of the board (although they have an arc). Grain var-
ies between these two extremes. Vertical-grain lumber has a
grain angle from 90° (growth rings perpendicular to surface)
to approximately 45°. From 45° to the other extreme (board
c), lumber is considered flat grain. Board b is different.
Lumber cut close to the pith (the center of the log) contains
abnormal wood cells. These abnormal cells are juvenile
wood and have extremely high longitudinal dimensional
change (2%) compared with normal wood (0.1–0.2%). The
values are the change from green to ovendry (see Chap. 4).
A 10-ft (3-m) board could shrink 2.4 in. (61 mm). This
dimensional instability leads to severe warping and cross-
grain checking in lumber containing juvenile wood (see
Chap. 5).
The bark side and pith side of flat-grain or flat-sawn lum-
ber have slightly different properties. The pith side is more
prone to have raised grain than the bark side, particularly
with abrupt-transition wood species (southern yellow pine,
Douglas-fir, and oak (Table 16–1)). The bark side tends to
check more, and the checking is more pronounced in the
LW bands.General Technical Report FPL–GTR– 190(a) (b)(c) (d)(e) (f)(g) (h)Figure 16–5. Wide LW bands characteristic
of (a) the southern yellow pines, (b) radiata
pine, and (c) Douglas-fir and narrow LW
bands characteristic of (d) white pine, (e)
redwood, and (f) western redcedar; (g) and
(h) are examples of the difference in surface
texture between diffuse-porous and ring
porous hardwoods, respectively; (e) shows
examples of second or third growth (left)
and old-growth (right) redwood.