American Hardwood Measuring & Grading
Introduction to Grading
With some exceptions, hardwood lumber is graded on the basis of the size and number of cuttings (pieces) which can be obtained from a board when it is cut up and used in the manufacture of hardwood products such as furniture, flooring, or mouldings and joinery. Usually the buyer intends to use only the clear (defect free) material in a board. A higher grade would have a larger area of clear wood.
Because the grading rules are based on the yield of clear wood, many of the beautiful, natural characteristics which appear in board are not included in the calculation of the yield. Often, the natural beauty and real bargains are not found in the most expensive grade of lumber. The keen buyer who will examine the lower grades can discover that they may yield the prize pieces.
Basic Yield for FAS
FAS (First and Seconds). The FAS grade will provide the user with long, wide, clear cuttings. Best suited for high quality furniture, interior joinery and solid wood mouldings. The FAS grade includes a range of boards which yield from 83.33%
(10/12) to 100% clear wood cuttings at least 3 wide by 7 long or 4 wide by 5 long. See diagram below.
FAS 1F or Selects
In FAS 1F (FAS One FACE) and Selects, the grade is established using both faces of the board. The best face must meet the requirements for FAS, and the reverse side must essentially grade No.1. FAS 1F and Selects are virtually the same grade, except for minimum width and length. The minimum board size for selects is 4x6; and for FAS it is 6x8.
Basic Yield for No.1 Grade
No.1 will provide the user with clear cutting of medium length and width. Best suited for furniture, cabinets and a multitude of solid wood manufactured products. The No.1 grade includes a range of boards which will yield from 66.66%
(8/12) to 83.33% (10/12) clear wood in cuttings at least 3 wide by 3 long or 4 by 2. Please see diagram below.
Basic Yield for No.2 Grade
No.2 will provide the user with short, narrow clear cuttings economically priced, for use in unexposed furniture frames, picture frames, cabinet rails and frames, parquet or strip flooring, and many other smaller solid wood components. The No.2a grade includes a range of boards which yield from 50% (6/12) to 66.66% (8/12) clear wood in cuttings at least 3 wide by 2 long.
This grade is included in the general classification of No.2 Common, but 2a should be specified if clear cuttings are required.
Measuring Hardwoods - Random Widths and Lengths
Surface Measure (SM)
The surface area of a board in square feet. To determine surface measure, multiply the width of the board in inches by the length in feet, and divide the product by 12, rounding off to the nearest whole number.
Some examples of surface measure calculations are as follows:
8 x 12 χ 12 = 8 = 8 SM
6 1/2 x 8 χ 12 = 4 1/3 = 4 SM
10 x 13 χ 12 = 10 10/12 = 11 SM
Most board rules today (lumber scaling sticks), take this averaging into account automatically. The graduations on the board rule measure from the half-foot mark to the next half-foot mark, therefore all boards falling into the range are shown as a whole number.
Board Foot (bd.ft or BF)
A board foot is the unit of measurement of lumber. A board foot is one foot long, one foot wide and one inch thick, or its equivalent.
The formula for determining board feet in a board is:
(Width in inches x length in feet x thickness in inches) χ 12 = BF
(12W x 12L x 1T) χ 12 = 12 bd.ft
(6W x 16L x 2T) χ 12 = 10 bd.ft
(8W x 6L x 2T) χ 12 = 8 bd.ft
The board foot measure of 1 thick boards is equal to the surface measure, (note rounding convention):
(9W x 9L x 1T) χ 12 = 63/4 = 7 bd.ft
(10W x 10L x 1T) χ 12 = 81/3 = 8 bd.ft
(7W x 11L x 1T) χ 12 = 6.42 = 6 bd.ft
1. Lumber measurement is based on thickness before surfacing.
2. When measuring hardwood lumber, lengths less than a full foot
are measured as the next lower foot length. (a board 99 ismeasured as just 9 long.)
Measuring With a Board Rule
1. Place the flange of the rule on the edge of the board, 1/3 of the length up from the narrow end.
2. Read to the right edge of the board, on the line indicating the boards length, for the board feet in lumber 1 thick and less. The board rule reads, for this example:
16 length = 6BF
14 length = 5BF
12 length = 4BF
For 8 lumber, read 1/2 the 16 scale: 8 length = 3BF
Kiln-Dried Hardwood Lumber Measurement
Measurement after Kiln Drying
Sales of Hardwood lumber measured after kiln drying shall be quoted, invoiced, and delivered on the basis of net board footage.
Measurement before Kiln Drying
Sales of Hardwood lumber measured prior to kiln drying shall be quoted, invoiced, and delivered on the basis of net board footage before kiln drying.
Far Eastern hardwood measuring and grading
This is covered by The Malaysian Grading Rules (MGR) which are designed for grading all hardwood timbers (except Teak) from Malaysia or adjacent territories.
The UK market takes primarily the top end grades with other markets (particularly Far Eastern) taking the lower grades. In order to get a consistent supply of the upper grades to the UK, the other markets must be equally demanding for the lower grades as one cannot be produced without the other.
There are six grades that cover sawn timber: Prime, Select, Standard, Sound, Serviceable and Utility. Each different grade has specific requirements but there are some important factors that apply to more than one grade.
Splits: This is a defect that should be excluded from all cuttings, but in any case must not exceed in aggregate length, in inches, the length of the piece in feet. Splits can only be straight if present in a piece (straight meaning less than 1 deviation from parallel per foot in length of split).
No piece may contain heart or borer holes.
No piece may contain decay.
Wane, other than a slight silver on the corner, is not allowed in any piece except in Serviceable and Utility Grade.
Brittle heart is not allowed in any piece except in Serviceable and Utility Grade.
The different grades are as follows:
Specification Widths 6 and wider Lengths 6 and longer.
Sapwood Whether this is bright or not it must be excluded from
clear face cuttings.
Knots The average diameter of any sound knot must not exceed
one third of the width of the face on which it appears.
Spring This should not exceed 1 per 12 in length.
Warp Not admitted if sufficient to prevent the whole piece from
being surfaced two sides to a standard surfaced thickness.
Cutting Requirements The number of clear face cuttings required
to make the grade will vary according to the size of the piece. 1
cutting from a piece of 3-4 9ft2 to 5 cuttings from any piece of 14
ft2 and over.
Specification Widths 5 and wider, Lengths 6 and longer
Sapwood Unless it is greater in total than one third the width of the piece, or is present in both faces, bright sapwood will not be counted as a defect and may be included in clear face cuttings.
Knots As prime grade
Spring As prime grade
Warp Other than spring, has the same restrictions as Prime Grade. Wider pieces (greater than 10) can be allowed if when ripped to produce two pieces they would fall within both the Select Grade and warp restrictions.
Cutting Requirements The number of clear face cuttings in this grade varies from 1 cutting from any piece 4.9 ft2 or less. The minimum size of clear cutting must be 4 x 3 = 12 units or 3 x 4 = 12 units.
Specifications Width 4 and wider, Lengths 6 and longer.
Sapwood Bright sapwood is not counted as a defect in this grade.
Knots The average diameter of any sound knot must not exceed half the face width of the piece.
Spring Should not exceed 1 per 8 in length.
Warp Other than spring, it is not admitted within the grade if it is sufficient to prevent surfacing requirements but this applies to the clear face cuttings only and not the whole piece.
Cutting Requirements The number of clear face cuttings varies from 1 cutting from any piece 2-4.9 ft2 to 5 cuttings from any piece 14 ft2 or over. The minimum size for a clear face cutting in this grade must be 3x3 = 9 units or 4x2 = 8 units.
Otherwise known as BHND (Borer Hole No Defect). As for Prime, Select and Standard grades except that pin and unstained shot holes are allowed in the cuttings.
Specification Widths 4 and wider, Lengths 6 and longer.
Wane Allowed on the worst face and one edge only as follows: in widths of 6 and up, the wane should not exceed 1/6 the width of the piece, and in width less than 6 it should not exceed 1/8 the width of the piece.
Brittle Heart Allowed on one face and edge only so long as the strength of the piece is not materially affected. It may also be included in the cuttings.
Spring As Standard grade.
Warp As Standard grade.
Cutting Requirements As for Standard grade except cuttings are to be Sound face cuttings with brittle heart allowed.
Outside the cuttings will allow splits, wane and any sound defect not materially affecting the strength of the timber (all within earlier restrictions).
Specification Widths 4 and wider, Lengths 6 and longer.
Wane Allowed on the worst face and one edge only and not exceeding 1/4 width of the piece.
Brittle Heart As Serviceable grade.
Spring As Standard grade.
Warp As Standard grade.
Splits As Standard grade.
Cutting Requirements All pieces to meet sound face cutting requirements with wane, brittle heart and splits as above and any sound defect not materially affecting the strength of the timber.
Grading System used for MGR
Grades are determined under one or other of the following systems.
This is normally used when grading timber for special purposes and used in the sizes in which supplied. Permissible defects are defined for each grade later.
Used for grading timber that is usually re-sawn to smaller sizes before use. The grade is determined from the worst face of the piece except when otherwise specified. The percentage of the total surface area of that face can be included in limited number of cuttings (Clear Face or Sound Face) determines the grade. The best grades yield the highest percentage of Clear Face Cuttings.
Clear Face or Sound Face cutting are defined in the glossary of terms.
Areas of cutting are determined by using Units of cutting. A unit of cutting is an area 1 inch wide by 1 foot long = 12 square inches and hence to find the number of units in a cutting multiply the length in feet (to the nearest foot) by the width in inches (to the nearest inch).
The following examples illustrate the grading system in action.
A board is 9x16 (= 12 square feet) and it is found that it can be marked as shown in the diagram below to give the following Clear Face Cuttings:
9 x 76 = 67.5 units
5 x 8 = 40 units
4 x 66 = 26 units
Total 133.5 units
The grade specification shows that a board of this size must yield at least 10/12 120 units clear in two cuttings of no less than 5x4 or 4x5 in size, or 11/12 132 units clear in three cuttings in order to grade as Prime; this board gives more than 132 units clear in three cuttings over 5x4 or 4x5 in size so it grades as Prime grade.
Another board of the same size (9x16) contains more defects, and only yields the Clear Face Cuttings shown in the diagram below:
7 x 4 = 28 units
8 x 3 = 24 units
5 x 66 = 32.5 units
4 x 6 = 24 units
Total 108.5 units
The grade specification shows that a board of this size must yield
at least 9/12 = 108 units clear in four cuttings of not less than 4x3 or 3x4 in size order to grade as Select; this board gives more than 108 units clear in four cuttings over the required size, so it grades
as Select grade.
Grouping of Grades
Most timber exported from Malaysia is classified by grouping certain
grades together and using one mark and price to cover this. Each
grouping is called by the lower grade used with and better showing that better grades are included.
Normal groupings are as follows:
i Select and Better should normally include the full product of the
log in Select and better grades.
ii Standard and Better as above but starting at standard grade.
iii Sound & Better as above but starting at sound grade.
iv Serviceable & Better as above but starting at serviceable grade.
v Merchantable utility grade upwards (hence also Utility and
Better). Thus this is a group of all grades providing timber of high
quality and normal run of the mill since only the very worst pieces
will be rejected during grading.
The mix of each grade within each grouping will vary from species to species and from mill to mill.