ASTM D245-00(2002)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
e1
Designation: D 245 – 00 (Reapproved 2002)
Standard Practice for
Establishing Structural Grades and Related Allowable
Properties for Visually Graded Lumber
This standard is issued under the fixed designation D 245; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Ref (9) was added in September 2002.
1. Scope 2. Referenced Documents
1.1 This practice (1,2) covers the basic principles for 2.1 ASTM Standards:
establishing related unit stresses and stiffness values for design D9 Terminology Relating to Wood
with visually-graded solid sawn structural lumber. This prac- D 143 Methods of Testing Small Clear Specimens of Tim-
tice starts with property values from clear wood specimens and ber
includes necessary procedures for the formulation of structural D 2555 Test Methods for Establishing Clear-Wood Strength
grades of any desired strength ratio. Values
1.2 The grading provisions used as illustrations herein are E 105 Practice for Probability Sampling of Materials
not intended to establish grades for purchase, but rather to E 380 Practice for Use of the International System of Units
show how stress-grading principles are applied. Detailed grad- (SI) (the Modernized Metric System)
ing rules for commercial stress grades which serve as purchase
3. Significance and Use
specifications are established and published by agencies which
3.1 Need for Lumber Grading:
formulate and maintain such rules and operate inspection
facilities covering the various species. 3.1.1 Individual pieces of lumber, as they come from the
saw, represent a wide range in quality and appearance with
1.3 The material covered in this practice appears in the
following order: respect to freedom from knots, cross grain, shakes, and other
characteristics. Such random pieces likewise represent a wide
Section
Scope 1
range in strength, utility, serviceability, and value. One of the
Significance and Use 3
obvious requirements for the orderly marketing of lumber is
Basic Principles of Strength Ratios 4
the establishment of grades that permit the procurement of any
Estimation and Limitation of Growth Characteristics 5
Allowable Properties for Timber Design 6
required quality of lumber in any desired quantity. Maximum
Modification of Allowable Properties for Design Use 7
economy of material is obtained when the range of quality-
Example of Stress-Grade Development 8
determining characteristics in a grade is limited and all pieces
1.4 The values given in parentheses are provided for infor-
are utilized to their full potential. Many of the grades are
mation purposes only.
established on the basis of appearance and physical character-
1.5 This standard does not purport to address all of the
istics of the piece, but without regard for mechanical proper-
safety concerns, if any, associated with its use. It is the
ties. Other grades, called structural or stress grades, are
responsibility of the user of this standard to establish appro-
established on the basis of features that relate to mechanical
priate safety and health practices and determine the applica-
properties. The latter designate near-minimum strength and
bility of regulatory limitations prior to use.
near-average stiffness properties on which to base structural
design.
3.1.2 Thedevelopmentofthispracticeisbasedonextensive
research covering tests of small clear specimens and of
This practice is under the jurisdiction of ASTM Committee D07 on Wood and
full-sized structural members. Detailed studies have included
is the direct responsibility of Subcommittee D07.02 on Lumber and Engineered
Wood Products.
Current edition approved April 10, 2000. Published June 2000. Originally
published as D 245 – 26. Last previous edition D 245 – 99. Annual Book of ASTM Standards, Vol 04.10.
2 4
The boldface numbers in parentheses refer to references at the end of this Annual Book of ASTM Standards, Vol 14.02.
practice. Annual Book of ASTM Standards, Vol 14.02 (excerpts in Vol 04.10).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
e1
D 245 – 00 (2002)
the strength and variability of clear wood, and the effect on ciency in some particulars, it offers the advantage of a more
strength from various factors such as density, knots (See simple system of grades of stress-graded lumber.
Terminology D9), and other defects, seasoning, duration of 3.4 Essential Elements in a Stress-Grade Description:
stress, and temperature. 3.4.1 Astress grade formulated by this practice contains the
following essential elements:
3.2 How Visual Grading is Accomplished— Visual grading
is accomplished from an examination of all four faces and the 3.4.2 Agrade name that identifies the use-class as described
in 3.3.
ends of the piece, in which the location as well as the size and
nature of the knots and other features appearing on the surfaces 3.4.3 A description of permissible growth characteristics
that affect mechanical properties. Characteristics that do not
are evaluated over the entire length. Basic principles of
structural grading have been established that permit the evalu- affect mechanical properties may also be included.
ation of any piece of stress-graded lumber in terms of a 3.4.4 One or more allowable properties for the grade related
strength ratio for each property being evaluated. The strength to its strength ratio.
ratio of stress-graded lumber is the hypothetical ratio of the
4. Basic Principles of Strength Ratios
strength property being considered compared to that for the
4.1 General Considerations:
material with no strength-reducing characteristic. Thus a piece
4.1.1 Strength ratios associated with knots in bending mem-
of stress-graded lumber with a strength ratio of 75 % in
bers have been derived as the ratio of moment-carrying
bending would be expected to have 75 % of the bending
capacity of a member with cross section reduced by the largest
strength of the clear piece. In effect, the strength ratio system
knot to the moment-carrying capacity of the member without
of visual structural grading is thus designed to permit practi-
defect. This gives the anticipated reduction in bending strength
cally unlimited choice in establishing grades of any desired
due to the knot. For simplicity, all knots on the wide face are
quality to best meet production and utilization requirements.
treated as being either knots along the edge of the piece (edge
3.3 Classification of Stress-Graded Lumber:
knots) or knots along the centerline of the piece (centerline
3.3.1 The various factors affecting strength, such as knots,
knots).
deviations of grain, shakes, and checks, differ in their effect,
4.1.2 Strength ratios associated with slope of grain in
depending on the kind of loading and stress to which the piece
bending members, and in members subjected to compression
is subjected. Stress-graded lumber is often classified according
parallel to grain, were obtained, experimentally (3).
to its size and use. Four classes are widely used, as follows:
4.1.3 Strength ratios associated with shakes, checks, and
3.3.1.1 Dimension Lumber—Pieces of rectangular cross
splits are assumed to affect only horizontal shear in bending
section, from nominal 2 to 4 in. thick and 2 or more in. wide,
members. These strength ratios were derived, as for knots, by
graded primarily for strength in bending edgewise or flatwise,
assuming that a critical cross section is reduced by the amount
but also frequently used where tensile or compressive strength
of the shake, or by an equivalent split or check.
is important. Dimension lumber covers many sizes and end
4.1.4 Strength ratios associated with knots in compression
uses.Lumbergradedforspecificendusesmaydictateaspecial
members have been derived as the ratio of load-carrying
emphasis in grading and require an identifying grade name.
capacity of a member with cross section reduced by the largest
NOTE 1—For example, in NorthAmerican grading under theAmerican
knot to the load-carrying capacity of the member without
Lumber Standards Committee, stress graded dimension lumber categories
defect. No assumption of combined compression and bending
that reflect end use include Light Framing, Structural Light Framing,
is made.
Structural Joists and Planks, and Studs.
4.1.5 Tensile strength of lumber has been related to bending
3.3.1.2 Beams and Stringers—Pieces of rectangular cross
strength and bending strength ratio from experimental results
section, 5 in. nominal and thicker, nominal width more than 2
(4).
in. greater than nominal thickness, graded for strength in
4.1.6 Strength in compression perpendicular to grain is little
bending when loaded on the narrow face.
affected in lumber by strength-reducing characteristics, and
3.3.1.3 Posts and Timbers—Pieces of square or nearly
strength ratios of 100 % are assumed for all grades.
square cross section, 5 by 5 in., nominal dimensions and larger,
4.1.7 Modulus of elasticity of a piece of lumber is known to
nominal width not more than 2 in. greater than nominal
be only approximately related to bending strength ratio. In this
thickness, graded primarily for use as posts or columns.
standard, the relationship between full-span, edgewise bending
3.3.1.4 Stress-Rated Boards—Lumber less than 2 in. nomi-
modulus of elasticity and strength ratio was obtained experi-
nal in thickness and 2 in. or wider nominal width, graded mentally.
primarily for mechanical properties.
4.1.8 In developing a stress-grade rule, economy may be
3.3.2 The assignment of names indicating the uses for the served by specifying strength ratios such that the allowable
various classes of stress-graded lumber does not preclude their stresses for shear and for extreme fiber in bending will be in
use for other purposes. For example, posts and timbers may balance, under the loading for which the members are de-
give service as beams. The principles of stress grading permit signed.
theassignmentofanykindofallowablepropertiestoanyofthe 4.1.9 A strength ratio can also be associated with specific
classes of stress-graded lumber, whether graded primarily for gravity. Three selection classes called dense, close grain, and
that property or not. Recommendations for allowable proper- medium grain are described herein, based on experimental
ties may include all properties for all grades or use classes. findings (5).
While such universal application may result in loss of effi- 4.2 Strength Ratios:
e1
D 245 – 00 (2002)
4.2.1 Table 1 gives strength ratios, corresponding to various 5. Estimation and Limitation of Growth Characteristics
slopes of grain for stress in bending and compression parallel
5.1 General Quality of Lumber:
to grain.
5.1.1 All lumber should be well manufactured.
4.2.2 Strength ratios for various combinations of size and
5.1.2 Only sound wood, free from any form of decay, shall
location of knot and width of face are given in Table 2, Table
be permitted, unless otherwise specified. Unsound knots and
3, and Table 4. Since interpolation is often required in the
limited amounts of decay in its early stages are permitted in
development of grading rules, the use of formulas in Table 2,
some of the lower stress-rated grades of lumber intended for
Table 3 and Table 4 is acceptable. These formulas are found in
light frame construction.
the Appendix.
5.1.3 In stress-grading, all four faces and the ends shall be
4.2.2.1 Use of the tables is illustrated by the following
considered.
1 1
example:Thesizesofknotspermittedina7 ⁄2by15 ⁄2-in.(190
5.2 Slope of Grain:
by 394-mm) (actual) beam in a grade having a strength ratio of
5.2.1 Slope of grain resulting from either diagonal sawing
70 % in bending are desired. The smallest ratio in the column
or from spiral or twisted grain in the tree is measured by the
fora7 ⁄2-in. (190-mm) face in Table 2 that equals or exceeds
angle between the direction of the fibers and the edge of the
70 % is opposite 2 ⁄8 in. (54 mm) in the size-of-knot column.A
piece. The angle is expressed as a slope. For instance, a slope
similar ratio in the column for 15 ⁄2-in. (394-mm) face inTable
of grain of 1 in 15 means that the grain deviates 1 in. (2.5 mm)
3isopposite4 ⁄4in.(108mm).Hence,thepermissiblesizesare
from the edge in 15 in. (381 mm) of length.
1 1
2 ⁄8 in. (54 mm) on the 7 ⁄2-in. (190-mm) face and at the edge
1 5.2.2 When both diagonal and spiral grain are present, the
of the wide face (see 5.3.5.2) and 4 ⁄4 in. (108 mm) on the
1 combined slope of grain is taken as the effective slope.
centerline of the 15 ⁄2-in. (394-mm) face.
5.2.3 Slope of grain is measured and limited at the zone in
4.2.3 For all lumber thicknesses, a strength ratio of 50 %
the length of a structural timber that shows the greatest slope.
shall be used for all sizes of shakes, checks and splits.A50 %
It shall be measured over a distance sufficiently great to define
strength ratio is the maximum effect a shake, check or split can
the general slope, disregarding such short local deviations as
have on the load-carrying capacity of a bending member.
those around knots except as indicated in 5.2.5.
Limitations in grading rules placed on the characteristics at
5.2.4 In 1-in. nominal boards (See Terminology D9), or
time of manufacture are for appearance and general utility
similar small sizes of lumber, a general slope of grain any-
purposes, and these characteristics shall not be used as a basis
where in the length shall not pass completely through the
for increasing lumber shear design values.
thickness of the piece in a longitudinal distance in inches less
NOTE 2—The factor of 0.5 (50 %) is not strictly a “strength ratio” for
than the number expressing the specified permissible slope.
horizontal shear, since the factor represents more than just the effects of
Where such a slope varies across the width of the board, its
shakes,checksandsplits.Thefactoralsoincludesdifferencesbetweentest
average may be taken.
values obtained in Methods D 143 shear block tests and full-size solid-
5.2.5 Local deviations must be considered in small sizes,
sawn beam shear tests. The strength ratio terminology is retained for
compatibility with prior versions of Practice D 245, but prior provisions and if a local deviation occurs in a piece less than 4 in. nominal
permitting design increases for members with lesser-size cracks have been
inwidthoronthenarrowfaceofapiecelessthan2in.nomina
...