Chapter 3.     Stacked Roundwood, Preservative-Treated
Products, and Construction Logs

Stacked Roundwood

      Cord Measure

           • Standard rough cord

            •Long cord

            •The unit

           • Face cord

            •Volume of solid wood in a cord

      Stere Measure

      Conversions Between Cords and Steres

      Cord and Stere Weight

Preservative-Treated Products

         Pole Measurement and Specifications

            •Dry, finished poles

            •Barky pole stock

      Pole Volume

           • AWPA methods

            •Manufacturers' volume tables by pole class

      Pole Weights

           • Estimating weight density

            •Manufacturers' pole shipping weight tables

        Piling Measurement and Specifications

            •Finished piles

            •Barky piling stock

      Piling Volume

      Piling Weights

      Conversion of Pole and Piling Measures to Metric Units

      Ties

      Lumber

Construction Logs

      Chapter 3. Stacked Roundwood, Preservative-Treated Products, and Construction Logs

Stacked Roundwood

Cord Measure

Standard Rough Cord.     A standard rough cord occupies 128 gross cubic feet (3.62 cubic meters) usually comprising 4 foot long split or unsplit roundwood, generally with bark, stacked in a pile 4 feet high and 8 feet long. In some situations, stacks of longer pieces (such as 8 foot lengths) are estimated in terms of standard rough cords.

Long Cord.     A long cord is made up of 5 foot long pieces in a stack 4 feet high and 8 feet long, occupying 160 gross cubic feet (4.53 cubic meters). The long cord is 1.25 times greater than the standard cord and is often used in the southern United States.

The  Unit.     The long cord is sometimes referred to as a unit. In some cases, this term refers to a cord comprising pieces 5' 3" long in a 4 foot high by 8 foot stack occupying 168 gross cubic feet (4.76 cubic meters).

Face Cord.     This term is sometimes used for firewood and refers to stove-length pieces in a 4 foot high by 8 foot stack. With 16 inch long pieces, a face cord occupies one-third the gross space (42.3 cubic feet) of a standard rough cord. With 24 inch long pieces, it occupies half the gross space (64 cubic feet) of a standard rough cord.

Volume of Solid Wood in a Cord.     These cord measures are not a very accurate indication of the actual solid wood volume, because the amount of air space occupied varies with the diameter, length, bark thickness, and condition of the pieces. Condition refers to crookedness as well as surface roughness caused by limbs.

        Table 3-1 shows that a standard cord of smooth, straight barky softwood bolts from the Great Lakes region ranged from 90 to 100 cubic feet when the midbolt diameter ranged from less than 6 to more than 12 inches (USFS 1935). The range for hard­woods was from 85 to 98 cubic feet, and use of 8 foot rather than 4 foot bolts reduced these figures by 2 to 3 cubic feet. When bolts were crooked, rough, and knotty, volume per cord was reduced by about 20 cubic feet.

        In practice, an average conversion factor of 85 cubic feet (2.41 cubic meters) of wood per standard rough cord is often assumed. The USFS assessment assumes 79.2 cubic feet per cord (Appendix 2). Due
to the factors affecting actual volume, the range around this average can easily be plus or minus 20 cubic feet. Table 3-2 shows the effect of species (bark thickness) and diameter on solid content of a standard rough cord (Worthington and Twerdal 1950). Cubic meter equivalents have been added by the author. The 85 cubic feet per cord factor is reached at 11 inches in hemlock and 15 inches in Douglas-fir. If bolts in a cord have been debarked, the values under the total column give a reasonable approximation of the solid wood content.

Stere Measure

        Countries on the metric system use the stere as the standard measure for stacked roundwood. A stere is a space that is one meter on a side, hence one gross cubic meter (35.315 cubic feet, 0.276 standard rough cord). The term stere is used to differentiate this gross space from a solid cubic meter of wood. In some places the term loose cubic meter is used rather than the term stere.

Table 3-1. Solid content of barky standard cord and stere.

Source: Adapted from USFS (1935) by Flann (1962). Original data in Imperial units; metric values added by the author.

Conversions Between Cords and Steres

        Table 3-3 summarizes conversions using the 85 ft³/cord and European solid contents of steres. FAO, in its Yearbook of Forest Products, uses the gross cubic volumes (128 ft³/cord and 1 m³/stere).

Cord and Stere Weight

        Table 3-2 also presents the green weight per cord for Douglas-fir and hemlock. In addition to factors affecting the solid volume of a cord, weight depends on moisture content and species specific gravity. Many organizations have shifted to weight scaling (see Chapter 2, pp. 34-35) to develop local weight factors to account for species and seasonal effects. Since many purchasers are not interested in bark, either the weight factors or the price paid may be adjusted for it.

        Chapter 1 (p. 10) presents procedures for esti­mating the weight of a cord or stere based on the solid wood volume, species specific gravity, and moisture content. The example also illustrates how bark weight can be included or excluded.

Preservative-Treated Products

Preservative treatments are often given to wood to enhance durability, fire retardant ability, and so forth. The major categories are round products such as poles and pilings and sawn products such as railroad ties and lumber treated for decking, sills, and similar applications. The reader should obtain a current copy of the American Wood-Preservers' Association Standards, which has information on various preservatives and retention rates in differ­ent applications. Poles and pilings are round structural members which require processing that includes debarking, peeling to desired shape, seasoning, and usually treatment with preserva­tives. They are relatively straight, free of large knots, and have growth rate (rings per inch) requirements for wood close to their surface. Finished products are commonly sold by the piece.

Source: Worthington and Twerdal (1950).

Note: Values may not sum due to rounding.

Source: Calculated by the author.                                 SWE  =  solid wood equivalent.

Pole Measurement and Specifications

Dry, Finished Poles.     Poles are placed in classes depending on minimum circumference at the top, minimum circumference 6 feet from the bottom (butt), and species. Table 3-4 presents specifications for species groups that include Douglas-fir and western redcedar; specifications for other species groups are available in the ANSI standard for poles (ANSI 1992).

        Classification of poles is based on load-bearing capacity, and the system is defined so a pole of given length and class has essentially the same load-bearing capacity regardless of species. This is why, for example, a 50 foot, class 1 Douglas-fir pole has a smaller circumference 6 feet from the butt than western redcedar (45.0 versus 49.5 inches). Douglas-fir is a stronger species and has less taper.

        Since poles are measured for classification while in the green condition, some shrinkage (about 2%) will occur due to seasoning by the manufacturer or while in service. This shrinkage is taken into account when classifying poles using dry meas-urements.

        Poles used for power transmission lines are from 55 to 125 feet long. Power distribution poles range from 30 to 50 feet. Those used for pole buildings are generally shorter than 30 feet.

Barky Pole Stock.     Pole manufacturers translate the finished pole specifications into tables that can be used by foresters and loggers in assessing the suitability of a tree for pole manufacture. Table 3-5 is an example for Douglas-fir. Each manufacturer has its own pole stock tables that reflect its  experience with the bark thickness and taper of a species obtained from a given region.

        For example, Table 3-4 shows that a 50 foot, class 1 pole must have a minimum top circumference of 27 inches and a minimum circumference 6 feet from the butt of 45 inches. Table 3-5 shows that this has been translated into a 9 inch minimum top diameter inside bark and a 53 inch minimum outside bark circumference 6 feet from the butt.

Pole Volume

AWPA Methods.     Two methods given in Standard F3 of the American Wood-Preservers' Association (AWPA 1992) for calculating cubic foot volume of individual poles are:

        V = 3 L (C_m / π)² 0.001818                            (1)

        V = 0.001818 L (D² + d² + Dd) f   (2)

where

        V         =      volume (ft³)

        π          =      3.14159

        C_m       =      midlength circumference,in inches

        D, d     =      butt and top diameters, in inches

        L          =      length, in feet

        f           =      correction     =  0.82 oak piles

                                                   =  0.93 southern pine piles

                                                   =  0.95 southern pine, red

                                                        pine poles

                                                   =  1.0 otherwise

        Formula 1 is the AWPA official method except for Douglas-fir, for which either method can be used. AWPA Standard F3 contains volume tables based on both formulas. Table 3-6 presents cubic feet per lineal foot factors based on Formula 2 when the correction f in the formula is set to 1.0. See Example 1. (In examples and AWPA tables, the effect of bark thickness is ignored.)

Formula 1

First, estimate C_m from the pole taper as follows:

 C_m = [(C₆ – π d) / (L – 6)] L / 2 + π d = [(38.5 – 3.14159 _* 9)

        / (25 –  6)] 25 / 2 + 3.14159 _* 9 = 35.0.

Then,  V = 3 L (C_m / π)² 0.001818 = 3 _* 25 (35.0 /
        3.14159)² 0.001818 = 16.9 ft³.

The AWPA table has a value of 16.8 ft³.

Formula 2

First, estimate the butt end diameter (D) from pole taper:

  D = [(C₆ / π – d) / (L –  6)] L + d  =  [(38.5 / 3.14159 – 9) /

        (25 –  6)] 25 + 9 = 13 inches.

Then, V = 0.001818 L (D² + d² + Dd)  =  0.001818 _* 25                 (132 + 92 + 13 _* 9) = 16.7 ft³.

Pole Weights

Factors influencing pole weight are: (1) pole volume; (2) specific gravity of species (Table 1-1); (3) moisture content of pole (MC_od of a dry pole is about 25%); and (4) preservative type and reten­tion. The latter three are combined to give the weight density (pounds per cubic foot) of a pole, which, multiplied by pole cubic volume, estimates shipping weight.

Estimating Weight Density (lb/ft³).     In the absence of actual manufacturers' data, weight density of a treated pole can be approximated by methods outlined in Chapter 1. Using Douglas-fir as an example, SGg  =  0.45, hence Table 1-2 yields about 35.1 lb/ft³ at MC_od = 25%. Assuming a pre­servative retention of 12 lb/ft³ brings the pole _{weight density to 47.1 lb/ft}³_{. Multiplying by the} volume of a pole in Table 3-7 yields an estimate of its shipping weight. The AWPA standard contains information on retention of various preservatives.

Manufacturers' Pole Shipping Weight Tables.     Manufacturers carefully monitor retention rates and shipping weights of their products. For a given pole size and treatment weight, tables of different manufacturers are quite similar. However, weight tables differ substantially according to species and type of treatment. Illustrative weight densities are shown below for treatments of Douglas-fir and western redcedar (source: L. D. McFarland Company) with pentachlorophenol or ACZA.

These densities assume a moisture content of 25%.

        These factors, multiplied by cubic foot volumes in Table 3-7, result in manufacturers' tables of shipping weights. For example, a 50 foot, class 1 Douglas-fir pole (47.0 ft³) has a shipping weight of 2,162 pounds when treated with 0.45 penta and 2,350 pounds when treated with 0.60 penta.

Piling Measurement and Specifications

        Conceptually, the procedures for piling are very similar to those for poles. However, pilings have a different specification system under ASTM D25-91 (ASTM 1991).

Finished Piles.     The original classification for piling listed classes A, B, and C, which gave the minimum circumference at the top and minimum and maximum circumference 3 feet from the butt according to species group and lengths. Table 3-8 presents these specifications. Class C is relatively uncommon in practice.

Source: L. D. McFarland Company, unpublished.

^aAllows for average bark. Heavy bark may reduce poles one class.  

        A different, more detailed classification has tables for two species groups:  southern yellow pine and Douglas-fir plus other species (ASTM D25-91). For each species group, there is one table that gives minimum top circumferences according to length and required minimum circumference 3 feet from the butt. A second table gives minimum circumferences 3 feet from the butt according to length and required minimum top circumference.

Barky Piling Stock.     Manufacturers translate the finished piling specifications into minimum requirements that adjust for bark thickness and taper. These are then used by foresters and loggers in assessing the suitability of a tree for piling. Table 3-9 is an example for Douglas-fir.

Piling Volume

        Methods are the same as discussed for poles. Table 3-6 gives cubic foot volume per lineal foot of various sizes of peeled piles. Using AWPA methods and Table 3-10, average cubic foot volumes are obtained for various lengths in each piling class.

Piling Weights

        The same procedure discussed for poles can be applied. Treated Douglas-fir piling generally contains 17 pounds of preservative per cubic foot of wood for land-based use and 20 pounds for saltwater use. Moisture content within 2 inches of the surface is about MC_od = 25%. Table 3-10 gives average weight factors for clear, peeled, untreated Douglas-fir piles. Adding the preservative retention per cubic foot and multiplying by the cubic foot volume yields an estimate of shipping weight.

Table 3-7. Average cubic foot volume of poles by pole class and length.

Source: L. D. McFarland Company, unpublished.

Source: ASTM D25-58 (ASTM 1958).

Source:  L. D. McFarland Company, unpublished.

Source: L. D. McFarland Company, unpublished.

Conversion of Pole and Piling Measures to Metric Units

        Generally, standard conversions of 35.315 ft³/m³  and 2.205 lb/kg (Appendix 1) can be used to convert the pole and pile volume and weights to metric equivalents.

Ties

        Railroad crossties are produced from many hardwood and softwood species from logs at least8 feet long with diameters exceeding 7 inches. These logs are sawn into rectangular cross section pieces that are treated with a pre­servative. There are three basic tie categories, the 8 foot crosstie and the longer switch and bridge ties. According to McCurdy and Case (1989), about two-thirds of all ties produced have a 7 by 10 inch cross section; no other size cross section exceeds 10% of production.

        The volume of a tie in cubic feet is simply the product of the cross section area, converted to square feet, times the length in feet. Board foot volume is estimated from the board foot formula for lumber described in Chapter 4. Weight estimates can be made using methods in Chapter 1 and adding the weight of the appropriate preservative (see p. 44).

        In their study, McCurdy and Case (1989) use average values of 40 BF for a crosstie and 63 BF for switch and bridge ties (Appendix 2). These trans­late to about 3.5 ft³ (0.10 m³) and 5.25 ft³ (0.15 m³ ) respectively.

Lumber

        The procedures described in Chapter 4 should be used in estimating preservative-treated lumber volume. To estimate weight, either obtain shipping weights from the manufacturer or add the retention in lb/ft³ (see AWPA 1992) to the wood weight density based on the species and moisture content (Chapter 1). Multiply the combined lb/ft³ by the cubic foot volume of the product.

Construction Logs

        Construction logs used in log buildings are often milled into a cross section shape that is uniform along the length of the piece. Volume can be obtained by finding the cross section area in square feet and multiplying by the length. Weight estimation uses methods discussed in Chapter 1.