# ASTM D6662-17

Designation: D6662 − 17Standard Specification forPolyolefin-Based Plastic Lumber Decking Boards1This standard is issued under the fixed designation D6662; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This specification covers polyolefin-based plastic lum-ber products for use as exterior residential decking boards.1.2 Plastic lumber products are currently made predomi-nantly with recycled polyolefin plastics (in particular high-density polyethylene) where the products are more or lessnon-homogenous in the cross-section. However, this specifica-tion is also potentially applicable to similar manufacturedplastic products made from other plastic and plastic compositematerials that have non-homogenous cross-sections.1.3 This specification details a procedure to calculate rec-ommended span lengths for spacing of support joists. Thisprocedure was developed using experimental data from atypical unreinforced plastic lumber made predominantly fromrecycled high-density polyethylene. The methodology to de-velop span lengths for other types and compositions of plasticlumber is detailed in Appendix X1 of this standard.1.4 The values are stated in inch-pound units, as these arecurrently the most common units used by the constructionindustry. Equivalent SI units are indicated in parentheses.However, the units stated for irradiance exposure in theweatherability section (6.3) are in SI units as these are the unitscommonly used for testing of this type.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1—There is no similar or equivalent ISO Standard.2. Referenced Documents2.1 The following documents of the issue in effect on thedate of material purchase form a part of this specification to theextent referenced herein:2.2 ASTM Standards:2D883 Terminology Relating to PlasticsD2565 Practice for Xenon-Arc Exposure of Plastics In-tended for Outdoor ApplicationsD2915 Practice for Sampling and Data-Analysis for Struc-tural Wood and Wood-Based ProductsD4329 Practice for Fluorescent Ultraviolet (UV) Lamp Ap-paratus Exposure of PlasticsD5033 Guide for Development ofASTM Standards Relatingto Recycling and Use of Recycled Plastics (Withdrawn2007)3D6109 Test Methods for Flexural Properties of Unreinforcedand Reinforced Plastic Lumber and Related ProductsD6112 Test Methods for Compressive and Flexural Creepand Creep-Rupture of Plastic Lumber and ShapesD6341 Test Method for Determination of the Linear Coef-ficient of Thermal Expansion of Plastic Lumber andPlastic Lumber Shapes Between –30 and 140°F (–34.4and 60°C)E84 Test Method for Surface Burning Characteristics ofBuilding MaterialsE108 Test Methods for Fire Tests of Roof CoveringsG151 Practice for Exposing Nonmetallic Materials inAccel-erated Test Devices that Use Laboratory Light SourcesG154 Practice for Operating Fluorescent Ultraviolet (UV)Lamp Apparatus for Exposure of Nonmetallic MaterialsG155 Practice for Operating Xenon Arc Light Apparatus forExposure of Non-Metallic Materials3. Terminology3.1 Definitions:3.1.1 plastic lumber, n—a manufactured product made pri-marily from plastic materials (filled or unfilled), typically usedas a building material for purposes similar to those of tradi-tional lumber, which is usually rectangular in cross-section.(Terminology D883)3.1.1.1 Discussion—Plastic lumber is typically supplied insizes similar to those of traditional lumber board, timber and1This specification is under the jurisdiction of ASTM Committee D20 onPlastics and is the direct responsibility of Subcommittee D20.20 on Plastic Lumber.Current edition approved March 1, 2017. Published March 2017. Originallyapproved in 2001. Last previous edition approved in 2013 as D6662 - 13. DOI:10.1520/D6662-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes section appears at the end of this standardCopyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1dimension lumber; however the tolerances for plastic lumberand for traditional lumber are not necessarily the same.(Terminology D883)3.1.2 resin, n—a solid or pseudo solid organic material oftenof high molecular weight, which exhibits a tendency to flowwhen subjected to stress, usually has a softening or meltingrange, and usually fractures conchoidally. (Terminology D883)3.1.2.1 Discussion—In a broad sense, the term is used todesignate any polymer that is a basic material for plastics.(1982)3.2 Definitions of Terms Specific to This Standard:3.2.1 bulge—convex distortion (away from the center of thecross-section) of the face of the board from a straight linedrawn from edge to edge across the width of the board.3.2.2 crook—distortion of the board in which there is adeviation in a direction perpendicular to the edge from astraight line from end to end of the board.3.2.3 cup—concave distortion (towards the center of thecross-section) of the face of the board from a straight linedrawn from edge to edge across the width of the board.3.2.4 edge—the side of a rectangular-shaped board corre-sponding to the thickness of the board.3.2.5 face—the side of a rectangular-shaped board corre-sponding to the width of the board.3.2.6 thickness—the lesser dimension of the cross-sectionalprofile of a rectangular-shaped board.3.2.7 width—the greater dimension of the cross-sectionalprofile of a rectangular-shaped board.3.3 Additional definition of terms applying to this specifi-cation appear in Terminology D883 and D5033.4. Ordering Information4.1 The information contained in this specification is in-tended to be helpful to producers, distributors, regulatoryagencies and users. The information can also promote under-standing between purchasers and sellers. The purchaser shallstate whether this specification is to be used, select thepreferred options permitted herein, and include the allowabledesign information in the invitation to bid and purchase orderfrom the following:4.1.1 Title, number and date of this specification,4.1.2 Minimum allowable bending strength and allowablebending stiffness,4.1.3 Percent recycled content (if requested),4.1.4 Flame spread index,4.1.5 Color,4.1.6 Quantity in lineal feet,4.1.7 Cut length,4.1.8 Cross-sectional dimensions,4.1.9 Packing requirements,4.1.10 Palletization, if required,4.1.11 Marking, if other than specified.4.2 If specific mechanical property values are not requiredby the purchaser (for example, when purchasing materials forgeneral retail sales distribution and not for a specific project),the manufacturer shall provide minimum allowable designinformation, as would be determined under this specification,to aid in the application of the decking board material by theend user.5. Dimensions and Permissible VariationsIt is permissible to produce decking boards either in sizesthat are similar to the standard dimensions of the woodindustry, or to proprietary dimensions designed by manufac-turers. This specification does not limit the dimensionalrange of production. For reference, the standards of thewood industry are as follows:5.1 Thickness—Unless otherwise specified in 4.1.8, boardsshall be:Nominal (in.) Actual (in.) Tolerance (in.)13⁄4 ±1⁄165⁄4 1±1⁄1621-1⁄2 ±1⁄16Tolerance on thickness of boards thicker than 2 inches(nominal) shall be 61⁄16 inch.5.2 Width of Boards—Unless otherwise specified in para-graph 4.1.8, board widths shall be:Nominal (in.) Actual (in.) Tolerance (in.)32-1⁄2 ±1⁄16431⁄2 ±1⁄16651⁄2 ±1⁄1687-1⁄4 ±1⁄1610 9-1⁄4 ±1⁄1612 11-1⁄4 ±1⁄16Tolerance on width of boards wider than 12 inches (nominal)shall be 61⁄16 inch.5.3 Length of Boards—unless otherwise specified in 4.1.7,boards up to 20 feet shall have tolerances of +1⁄2 inch or -1⁄16inch. Over 20 feet, the tolerances will be +1⁄2-inch or -1⁄16 inchper 20-ft of length or fraction thereof. Measurement of lengthsto be made at 73 6 2 °F and relative humidity of 50 6 5%.5.4 Flatness Tolerance—Board shall be flat with maximumcup or bulge in the board face limited to the tolerances in Table1. Linear interpolation of the values is acceptable for dimen-sions other than listed.5.5 Squareness—Unless a specially shaped member isspecified, the cross-section of all boards shall be visuallyrectangular (that is, the face and edge of the board areperpendicular to each other) and suited for the intendedpurpose.5.6 Crook—Crook shall conform to the tolerances in Table2. Linear interpolation of the values is acceptable for dimen-sions other than listed.5.7 Tongue and Groove—Boards shall be without tongueand groove unless otherwise specified in 4.1.8. Because of loadtransfer between adjacent boards, the methodology and equa-tions presented in section 6.1.4 for determining recommendedTABLE 1 Cup or Bulge Tolerances Relative to Nominal Width ofthe Board FaceFace Width, in. #4 in. 6 in. 8 in. 10 in. 12 in.Tolerance1⁄32 in.1⁄16 in.1⁄8 in.3⁄16 in.1⁄4 in.D6662 − 172maximum span lengths are not applicable to tongue and grooveboards. Manufacturers of tongue and groove decking boardsshall provide recommended span lengths based on soundengineering practice, taking into account some of the issuesdescribed in 6.1.4 below, as well as previous, in-serviceperformance history.6. Performance Requirements6.1 Flexural Properties:6.1.1 Test Procedure—D6109.6.1.2 Specimens Tested—A minimum of 15 specimens shallbe tested.6.1.3 Criteria—(1) The mean value of the secant flexuralmodulus at 1 % outer fiber strain estimated statistically towithin 5 % with 75 % confidence shall equal or exceed 50 000psi. Table 3 shows the number of specimens required toestablish the mean value at 75 % confidence interval with 65 % error using Practice D2915.(2) The 5 % lower tolerancelimit at 75 % confidence flexural stress at 3 % outer fiber strainshall equal or exceed 1000 psi. If any specimen fails prior toreaching 3 % strain, then the flexural strength at failure for thatspecimen shall equal or exceed 1000 psi. The 5 % lowertolerance limit at 75 % confidence is computed by subtractingK-times the standard deviation from the mean value, where Kis tabulated in statistics handbooks (and in Table 3 of PracticeD2915) as a factor for a one-sided tolerance limit for thedistribution. Table 4 shows the value of K for several samplesizes.NOTE 2—Many standards require a minimum sample size of approxi-mately 30 to balance testing costs against the large reductions in theallowable values for very small sample sizes.NOTE 3—A16 in. on center joist spacing is considered typical standardspacing for residential deck construction. While 50 000 psi is given as aminimum flexural modulus, a modulus greater than 50 000 psi ispotentially required for some decking board sizes in order to meet thisspacing when determining span lengths per the guidance presented in6.1.4 below. Alternatively, use span lengths less than 16 in. on center asneeded.NOTE 4—Concurrent to the development of this specification for PlasticLumber Decking, a Standard Guide for the Design and Construction ofPlastic Lumber Decking is being developed by Section D20.20.01 (underthe Subcommittee D20.20 on Plastic Products). This Standard Guide isexpected to be available sometime after this Specification has beenapproved and in use.6.1.4 Span Lengths—Recommended maximum span lengthsshall be determined using the following equations:For concentrated loads on boards which are continuous overa minimum of two spans (such as decking boards) as shown inFig. 1, the maximum recommended span shall be limited byeither the stress or the deflection formula as follow, whicheverprovides the lesser span:Stress Formula:L 5 ~64SFb !/~13P! (1)Deflection Formula:L 5 @~67E I!/~Pkα!#12 (2)For distributed (or uniform) loads on boards which arecontinuous over a minimum of two spans (such as deckingboards) as shown in Fig. 2, the maximum span shall be limitedby either the stress or the deflection formula as follow,whichever provides the lesser span:Stress Formula:L 5 @~8SFb !~144!/~qb!#12 (3)Deflection Formula:L 5 @~185E I!~144!/~qb kα!#13 (4)where:L = computed span length, in.,S = section modulus, in.3,Fb = allowable flexural stress as computed in 6.1.4.1, psi,P = concentrated load, lb,E = effective modulus of elasticity as computed in 6.1.4.2,psi,I = moment of inertia, in.4,k = factor used to limit deflection to L/k (for exampleL/360 with k = 360; or L/120 with k = 120),q = uniformly distributed load, lb/sq-ft,b = actual board width, in., andα = Creep Adjustment Factor = 1.5.NOTE 5—The attached commentary in Appendix X1 provides arationale for the Creep Adjustment Factor, α.6.1.4.1 Allowable Flexural Stress—The allowable flexuralstress, Fb , of the decking board is given as follows:Fb 5 ~Fb/FS!·CD·CT(5)TABLE 2 Crook Tolerances Relative to Nominal Length and Widthof the BoardLength in Feet #4in.Width6in.Width8 in. Width 10 in.Width12 in.Width4–63⁄8 in.1⁄4 in.3⁄16 in.1⁄8 in.1⁄8 in.81⁄2 in.1⁄2 in.3⁄8 in.1⁄4 in.3⁄16 in.103⁄4 in.5⁄8 in.1⁄2 in.7⁄16 in.3⁄8 in.12 1 in.7⁄8 in.13⁄16 in.3⁄4 in.9⁄16 in.14 11⁄4 in. 11⁄8 in. 1 in.7⁄8 in.3⁄4 in.16 11⁄2 in. 13⁄8 in. 11⁄8 in. 1 in.7⁄8 in.TABLE 3 Number of Specimens Required to Establish the MeanValue with an Error of ± 5 % with 75 % Confidence for VariousCoefficients of Variation (COV) in the Data SetCOV Range, % 10–15 15–20 20–25 25No. of Specimens, N 15 23 34 ~60TABLE 4 Value of K for Establishing the Lower 5 % LowerTolerance Limit with 75 % Confidence for Various Sample SizesNo. of Specimens, N 15 30 InfiniteValue of K 1.991 1.869 1.645FIG. 1 Schematic of Concentrated Load on Boards that are Con-tinuous Over Two SpansD6662 − 173where:Fb= the base flexural stress value for plastic lumber madeof HDPE-type polyolefins for normal duration loading(10 yr. duration), psi,FS = Factor of Safety = 1.5,CD= Load Duration Factor for flexural stress, presented inFig. 3 and Table 5, depends on the shortest-durationload in combination, applied either cumulatively orcontinuously, andCT= Temperature Factor, Table 6.Fb, the base flexural str