Building Design and Construction Handbook - Merritt - Ventech!

BUILDING MATERIALS 4.47
Shiplapped Lumber. Lumber that has been worked or rabbeted on both edges,
to permit formation of a close-lapped joint.
Patterned Lumber. Lumber that is shaped to a pattern or to a molded form.
Softwoods are also classified according to nominal size:
Boards. Lumber less than 2 in in nominal thickness and 2 in or more in nominal
width. Boards less than 6 in in nominal width may be classified as strips.
Dimension. Lumber from 2 in to, but not including, 5 in in nominal thickness,
and 2 in or more in nominal width. Dimension may be classified as framing, joists,
planks, rafters, studs, small timbers, etc.
Timbers. Lumber 5 in or more nominally in least dimension. Timber may be
classified as beams, stringers, posts, caps, sills, girders, purlins, etc.
Actual sizes of lumber are less than the nominal sizes, because of shrinkage and
dressing. In general, dimensions of dry boards, dimension lumber, and timber less
than 2 in wide or thick are 1 ⁄4 in less than nominal; from 2 to 7 in wide or thick,
1 ⁄2 in less, and above 6 in wide or thick, 3 ⁄4 in less. Green-lumber less than 2 in
wide or thick is 1 ⁄32 in more than dry; from 2 to 4 in wide or thick, 1 ⁄16 in more, 5
and 6 in wide or thick, 1 ⁄8 in more, and 8 in or above in width and thickness, 1 ⁄4
in more than dry lumber. There are exceptions, however.
Yard lumber is classified on the basis of quality as:
Appearance. Lumber is good appearance and finishing qualities, often called
select.
Suitable for natural finishes
Practically clear
Generally clear and of high quality
Suitable for paint finishes
Adapted to high-quality paint finishes
Intermediate between high-finishing grades and common grades, and partaking
somewhat of the nature of both
Common. Lumber suitable for general construction and utility purposes, often
given various commercial designations.
For standard construction use
Suitable for better-type construction purposes
Well adapted for good standard construction
Designed for low-cost temporary construction
For less exacting purposes
Low quality, but usable
Structural lumber is assigned modulus of elasticity values and working stresses
in bending, compression parallel to grain, compression perpendicular to grain, and
horizontal shear in accordance with ASTM procedures. These values take into account
such factors as sizes and locations of knots, slope of grain, wane, and shakes
or checks, as well as such other pertinent features as rate of growth and proportions
of summerwood.
Factory and shop lumber is graded with reference to its use for doors and sash,
or on the basis of characteristics affecting its use for general cut-up purposes, or
on the basis of size of cutting. The grade of factory and shop lumber is determined
by the percentage of the area of each board or plank available in cuttings of spec-