9-98 Section 912. Timber and Lumber
912.01 General Requirements
Timber and lumber, timber piles, posts and blocks for guardrails, sign posts, mailbox posts, guard posts, guide posts, fence posts, and timber for rustic construction must meet the requirements of this section. In case of a conflict between the American Wood Protection Association (AWPA ) and ASTM International ( ASTM) standards, the AWPA standards take precedence. Machine or manufacture mat erial, including bored holes, saw cuts, routs, and kerfs, to the required shape before applying preservative treatment. The commercial and common names for domestic hardwood and softwood timber and lumber are as specified in ASTM D1165.
912.02 Quality Control
A.General. The supplier is responsible for QC and inspection of material . Material must be graded before shipment in accordance with the grading rules of ASTM D245 and marked with the approved grading agency stamp showing the mill origin, species, and grade. The required grading agency stamp or marking must be legible on a wide face at the trimmed end before and after treating.
B.Inspection Prior to Preservative Treatment . Before treating timber and lumber, inspect material for quality, size, and straightness . This inspection does not waive the Department ’s right to inspect and reject material in accordance with subsection 105.05.
C.Inspection of Preservative Treatment . Inspect chemical preservatives, treatment processes, and treated material in accordance with AWPA M2, “Standard for Inspection of Wood Products Treated with Preservatives, ” and AWPA M3, “Standard Quality Control Procedures for Wood Preserving Plants, ” and other relevant AWPA standards . The treater must determine whether the preservatives that are used conform to the requirements. For single treatment charges, analyze the preservative at least once per charge. For consecutive treatments from the same working tank, analyze the first charge and at least one of every five additional charges, selected at random. Collect preservative samples that are representative of the solution used in the actual treatment process. MDOT Standard Specifications for Construction Section 912 9-99 D. Results of Treatment . Ensure that the treatment results, including preservative analysis and penetration and ret ention determinations, meet AWPA standards.
E.Inspection Records . Provide a signed inspection certificate for each material shipment . Provide copies of treatment records, analysis records , and other records ensuring that the tr eatment conforms to specificati on requirements to the Engineer upon request . Retain the records at the treatment plant for at least 5 years from the date the material is shipped to the project . Refer to AWPA M2 for required information.
F.Painting Treated Wood . Air season wood for at leas t 30 days and remove preservative dust from the wood before painting.
912.03 Field Treatment of Preservative Treated Material
A.General . Field treat saw cuts, routs, kerfs, holes, and other injuries to preservative-treated material occurring after pressure treatment by brushing, dipping, soaking, or coating. Do not spray . Saturate injuries with the field-treating solution. Fill bored holes with preservative. The Contractor may fill horizontal holes by temporarily plugging one end of a hole and using a bent funnel to pour preservative into the other end of the hole.
B.Preservative. Use a 2.0% solution of copper naphthenate, based on copper as metal, meeting the requirements for AWPA M4 for field treatment . Ensure that a State of Michigan Certified Commercial Pesticide Applicator applies the copper naphthenate.
912.04 Terminology Used in Timber and Lumber Specifications
Refer to ASTM D9 and AWPA M5, “Glossary of Terms Used in Wood Preservation ,” for additional wood and wood preservation terms. Annual Ring . Growth layer produced by the tree in a single growth year, including earlywood and latewood. Bark. Layer of a tree, outside the cambian, comprising the inner bark or thin, inner living part (phloem) and the outer bark or corky layer composed of dry, dead tissue. Bird Peck. Small hole or patch of distorted grain resulting from birds pecking through the growing cells in the tree. Bird peck usually resembles a carpet tack with the point toward the bark, and it is usually accompanied by discoloration extending for a consi derable distance along the grain and to a much lesser extent across the grain . The discoloration produced by bird peck causes what is commonly known as mineral streak. MDOT Standard Specifications for Construction Section 912 9-100 Boxed Heart . Term used when the pith falls entirely within the four faces of a piece of wood anywhere in its length. Also called boxed pith. Check. Lengthwise separation of the wood that usually extends across the rings of annual growth and commonly results from stresses set up in wood during seasoning. Checks are measured as an average of the penetration perpendicular to the wide face. Where two or more checks appear on the same face, only the deepest one is measured. Where two checks are directly opposite each other, the sum of their depths is used. Contiguous Checks . Individual checks that are adjoining though not in contact with adjacent checks. Crook or Sweep . Distortion of a piece of lumber or post in which there is a deviation in a direction perpendicular to the edge from a straight line from end to end of the piece. Decay . Decompos ition of wood substance caused by action of wood destroying fungi, resulting in softening, loss of strength and weight , and often in change of texture and color. Advanced (or typical) Decay . Older stage of decay in which the destruction is readily recogniz ed because the wood has become punky, soft and spongy, stringy, ring-shaked, pitted, or crumbly . Decided discoloration or bleaching of the rotted wood is often apparent. Incipient Decay . Early stage of decay that has not proceeded far enough to soften or otherwise perceptibly impair the hardness of the wood. It is usually accompanied by a slight discoloration or bleaching of the wood. Defect . Any irregularity or imperfection occurring in or on the wood that may lower its durability or strength. Grain. Direction, size, arrangement, appearance, or quality of the fibers in wood or lumber. Heartwood . Wood extending from the pith to the sapwood, the cells of which no longer participate in the life processes of the tree. Heartwood may be infiltrated with gums, resins, and other materials that usually make it darker and more decay resistant than sapwood. Knot . Portion of a branch or limb that has been surrounded by subsequent growth of the wood of the trunk or other portion of the tree. As a knot appears on the sawed surface, it is merely a section of the entire knot, its shape depending on the direction of the cut . Knot diameter is measured as shown in Figure 912-1 . The smallest dimension is used to determine size of the knot. MDOT Standard Specifications for Construction Section 912 9-101 Figure 912 -1: Measurement of Timber / Lumber Defects Knot Cluster . Three or more knots in a compact, roughly circular group, with the grain between them highly contorted. Two or more knots arranged laterally and without contortion of the fibers between them do not constitute a knot cluster. Loose Knot . Knot that is not held firmly in place by growth or position and that cannot be relied upon to remain in place. Sound Knot . Knot that is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay. Unsoun d Knot . Knot that, due to decay, is softer than the surrounding wood. Mineral Streak. Olive to greenish- black or brown discoloration of undetermined cause in hardwoods, particularly hard maples; commonly associated with bird pecks and other injuries; occur s in streaks usually containing accumulations of mineral matter. MDOT Standard Specifications for Construction Section 912 9-102 Peeling (clean) . Removal of all outer bark and at least 80 % of the inner bark distributed over the surface of the post, pile, or block. Pith. Small, soft core in the structural center of a tree trunk, branch, twig, or log. Plugged Hole . Any opening, or defect, that has been filled or repaired through the use of wooden plugs, plastic wood, or other methods . Holes resulting from the taking of test cores by an increment borer to check penetration or retention of preservative and filled with tight -fitting pressure treated plugs are not considered plugged holes for rejection purposes. Sapwood . Living wood of pale color near the outside of the log. Under most conditions , sapwood is more susceptible to decay than heartwood. Shake. Separation along the grain, the greater part of which occurs between the rings of annual grow th. Shakes are measured at the ends of pieces between lines parallel with the two faces that give the smallest dimension. Slope of Grain . Deviation of the wood fiber from a line parallel to the edges of a piece. The deviation is expressed as a ratio, such as a slope of grain of one in eight . Generally, slope of grain is measured over sufficient length and area to be representative of the general slope of the fibers, disregarding local variations. Split . Lengthwise separation of the wood extending through the piece from one surface to an opposite or to an adjoining surface due to the tearing apart of wood cells . Splits are measured as the penetration of a split from the end of the piece and parallel to edges of the piece. Twist . Distortion caused by the turni ng or winding of the edges of a board so the four corners of any face are no longer in the same plane. Unsightly Gaps. The term as used in these specifications is interpreted as being any gap or opening that is more than ⅜ inch at its maximum width and mor e than 12 inches long. Wane . Bark or lack of wood from any cause on edge or corner of piece.
912.05 Structural Timber and Lumber
A.Grade. Provide structural timber and lumber of the grade required as determined by the grading and dressing requirements of ASTM D245.
B.Species. Use species included in AWPA U1, table in Section 5, “Species Names and Listings in U1 – Use Category System: User Specification for Treated Wood Products .” MDOT Standard Specifications for Construction Section 912 9-103 C. Preservative Treatment . Condition and treat structural timber and lumber in accordance with AWPA U1, Commodity Specification A . Refer to Use Category 4A (UC4A) for above-ground requirements and Use Category 4C (UC4C) for ground-contact requirements.
D.Preservatives. Provide preservatives meeting the requirements of AWPA U1, Section 4, “Standardized Preservatives (Informative)” and the relevant P Standards.
912.06 Timber Piles
A.Physical Characteristics and Species. Provide timber piles of southern pine, red pine, jack pine, ponderosa pine, Douglas -fir, western larch, lodgepole pine, or red oak . Before applying preservative treatment, ensure that timber piles meet the requirements of ASTM D25 except as modified by this subsection.
B.Dimensions . Ensure that the pile circumference measured under the bark meets the requirements of Table 912-1, except t hat 10% of the piles in a shipment lot may have circumferences 2 inches less than the minimum values. Ensure that piles do not exceed the 1:2 maximum to minimum diameter ratio measured at the butt of the pile. MDOT Standard Specifications for Construction Section 912 9-104 Table 912- 1: Circumferences and Diameters of T imber Piles Timber Pile Length (feet) 3 feet from Butt At Tip Minimum Maximum Minimum Circum . (inch) Diameter (inch) Circum . (inch) Diameter (inch) Circum . (inch) Diameter (inch) Douglas -fir, larch, pine, or tamarack <40 38 12 63 20 25 8 40–50 38 12 63 20 22 7 ≥50–70 41 13 63 20 22 7 ≥70–90 41 13 63 20 19 6 >90 Dimensions must be as specified in the proposal or on the plans . Oak or cypress <30 38 12 57 18 25 8 30–40 41 13 63 20 22 7 >40 41 13 63 20 19 6
C.Sapwood . Provide piles with a sapwood thickness of at least 1 inch at the butt end.
D.Straightness. Use straight piles as determined by drawing a line from the center of the butt to the center of the tip and ensuring the line lies within the pile body . Use only piles with a uniform taper from butt to top and without short crooks.
E.Knots . Provide piles free of unsound and loose knots . Piles may contain sound knots no greater than 4 inches in diameter or one-third of the shortest pile dimension at the knot location, except for piles used as structural members in exposed work . Ensure that piles used as structural members in exposed work do not contain sound knots with diameters greater than one-fourth of the shortest pile dimension at the knot location.
F.Checks. Do not use piles wi th checks wider than ¼ inch or deeper than 2 inches.
G.Peeling (Shaving) . Piles must meet the requirements for clean- peeled posts as specified by subsection 912.07.I.
H.Preservative Treatment . Perform preservative treatment of timber piling in accordance with the AWPA Use Category UC4C for foundation, land, and fresh water exposure. Submit certification from the treatment plant stating type, pressure process used, net amount of preservat ive retained and compliance with relevant standards to the Engineer . Preservative penetration and retention must meet the requirements of AWPA U1 Table 3.0, Use Category 4 (UC4C). MDOT Standard Specifications for Construction Section 912 9-105 I. Preservatives. Provide preservatives for treatment meeting the requirements of AWPA U1 , Section 4, “Standardized Preservatives (Informative)” and the applicable P Standards.
912.07 Timber Posts
A.General . Use posts cut from live timber without bird pecks or insect holes . Saw post ends square.
B.Species and Grades. Provide fence posts, guide posts, guard posts, and mailbox posts manufactured from the species specified in Table 912-2. Table 912- 2: Species and Grading Requirements for Posts Species Round Posts Grade Grading Rules Agency Hardwoods ASTM D245 MDOT Red oak ( northern r ed, black, pin laurel, c herry -bark, s carlet, water, willow oaks)(a) Hard m aple ( black and s ugar) , red m aple White ash White- heartwood beech Yellow birch Softwoods Northern white c edar, r ed pine, eastern white pine ( northern white pine) No. 1 or better NHPMA Douglas -fir No. 2 or better WCLIB, WWPA Southern pine s pecies No. 2 or better SPIB NHPMA = Northern Hardwood and Pine Manufacturers Assoc iation SPIB = Southern Pine Inspection Bureau WCLIB = West Coast Lumber Inspection Bureau WWPA = Western Wood Products Assoc iation
a.Southern red oak is not permitted.
C.Marking . Ensure that posts show the grading agency stamp indicating the mill origin, species, and grade.
D.Dimensions . Provide 7 -foot-long line posts with a nominal 4-inch-square cross section or a round cross section with a diameter of at least 4½ inches. Provide 8 -foot-long end, corner, gate, intersection, and intermediate braced posts with a nominal 6 -inch-square cross section or a round cross section with a diameter of at least 8 inches. MDOT Standard Specifications for Construction Section 912 9-106 Provide mailbox posts at least 6 feet long with a nominal 4-inch-square cross section or a round cross section with a diameter of at least 4 inches.
E.Dimensional Tolerances. Provide round posts within +¾ inch and −¼ inch of the required diameter . Ensure that posts are equal to the required nominal length ±2 inches . Use the average top diameter to determine the sizes of posts that are not perfectly round. Provide square posts w ithin −¼ inch of the required cross section.
F.Decay . Do not provide posts with butt rot in greater than 5 % of the butt area. Ensure that post tops a re sound, except that the Engineer may allow one pipe rot no greater than ⅜ inch in diameter in posts with a nominal top size of at least 6 inches.
G.Knots . Posts may contain sound knots trimmed flush with the post surface that do not affect the post strength.
H.Crook or Bow . Do not provide posts with short crooks, one- way sweep greater t han 2 inches, and unsightly and exaggerated winding twists.
I.Surface. Provide fence posts that are peeled or shaved to remove the outer bark from the entire length. Shaving to remove the inner bark is not required. Completely remove the inner and outer bark from round posts for mailbox posts, guard posts, and guide posts .
J.Preservative Treatment . Condition and treat round posts, except northern white cedar, in accordance with AWPA U1, Section 6, Commodity Specification B, Use Category 4B (UC4B) . Treat sawn posts as specified in subsection 912.05.C.
K.Conditioning . If air seasoned, stack posts in a Department -approved manner until the average moisture content is no greater than 19% .
L.Preservatives. Provide treatment preservatives meeting the requirements of AWPA U 1, Section 4, “Standardized Preservatives (Informative)” and the relevant P Standards.
M.Results of Treatment . Refer to Table 912-3 for the minimum preservative penetration and retention as determined in accordance with AWPA standards. MDOT Standard Specifications for Construction Section 912 9-107 Table 912- 3: Treatment Results Requirements: Preservative and Minimum Retention Preservative Minimum Retention 0.0–0.6 in ch zone AWPA Standard Oil type AWPA Commodity Specification B Table 3.1.2; use category 4B A 6 Waterborne type A 11 Minimum Penetration Species Heartwood Sapwood Hardwoods and Douglas -fir ≥0.3 inch 0.6 inch or 90%, whichever is greater Softwoods — 2.0 inch or 90%, whichever is greater
912.08 Sawn Timber Posts and Blocks for Beam Guardrail and Highway
Signs
A.Species and Grades. Provide wood posts for guardrail in accordance with Table 912- 4; for wood blocks in accordance with Table 912- 5; and for sign posts in accordance with Table 912- 6. Ensure that the grading agency stamp is applied to the middle one-third of each sign post on the wider face. Table 912- 4: Species and Grading Requirements for Sawn Timber Guardrail Posts Species Posts and Timber Grade Grading Rules Agency Hardwoods Grade GRP MDOT Red oak ( northern r ed, black, pin, laurel, c herry -bark, s carlet, water, and willow oaks)(a) Hard m aple ( black and s ugar) and red m aple White ash White- heartwood beech Yellow birch Hickory ( mockernut, pignut, shagbark, and s hellbark hickories) Softwoods Douglas -fir, Douglas -fir/larch No. 1 or better WWPA or WCLIB Southern pine No. 1 or better SPIB Jack pine 8 in × 8 in No. 1 or better NHPMA
a.Southern red oak is not permitted. MDOT Standard Specifications for Construction Section 912 9-108 Table 912- 5: Species and Grading Requirements for Sawn Timber Guardrail Blocks Species Blocks Grade Grading Rules Agency Hardwoods Grade GRB MDOT Red oak ( northern r ed, black, pin, laurel, ch erry-bark, s carlet, water, and willow oaks)(a) Hard m aple ( black and s ugar) and red m aple White ash White- heartwood beech Yellow birch Hickory ( mockernut, pignut, shagback, and s hellbark hickories) Softwoods Douglas -fir and Douglas -fir/larch No. 2 or better WCLIB, WWPA Southern pine s pecies No. 2 or better SPIB Jack pine, ped pine, and eastern white pine ( northern white pine) No. 1 or better NHPMA
a.Southern red oak is not permitted. Table 912- 6: Species and Grading Requirements for Sawed Sign Posts Posts Species Grade Grading Rules Agency 4 × 6 in ch (nominal) posts Balsam fir No. 1 (Joists -Planks) NELMA Douglas -fir No. 1 (Joists -Planks) WCLIB Eastern hemlock No. 1 (Joists -Planks) NHPMA Tamarack ( eastern l arch) No. 1 (Joists -Planks) NHPMA Eastern white pine Select Structural (Joists -Planks) NELMA Southern pine No. 1 (Joists -Planks) SPIB 6 × 8 in ch (nominal) posts Douglas -fir No. 1 Dense (Posts -Timbers) WWPA Southern pine No. 1 SR (Stress -Rated Timbers) SPIB Eastern hemlock Select Structural (Posts -Timbers) NELMA Tamarack ( eastern l arch) Select Structural (Posts -Timbers) NELMA MDOT Standard Specifications for Construction Section 912 9-109 For guardrails, provide wood posts and blocks with a nominal 6- by 8-inch cross section, except for jack pine provide at least No. 1 Grade posts with a nominal 8- by 8-inch cross section.
1.MDOT Grade GRP . Provide MDOT Grade GRP (guard rail posts ) meeting the requirements of this subsection.
a.Splits . Ensure splits are no greater than 3 inches on the bolt hole plane and no greater than 6 inches in other locations.
b.Checks. Ensure single checks are no deeper than 3 inches. Ensure checks opposite each other do not have a total depth greater than 3 inches as measured with a probe no greater than 1/16 inch thick and 1/16 inch in diameter. Ensure single checks at least ⅜ inch wide, as measured at the widest point, do not extend along more than one-third of the post length. Ensure single checks, as measured at the widest point, are no greater than ⅜ inch wide.
c.Shakes. Ensure shakes are no greater than 2 inches in the smallest dimension.
d.Splits, Checks, and Shakes. Ensure splits, checks, or shakes do not appear in combinations that may cause posts to separate into pieces.
e.Stains . Ensure pieces do not contain more than 25% stained heartwood, and staining is not caused by decay.
f.Slope of Grain . Ensure that the slope of grain is no greater than 1:10.
g.Wane . Ensure that wane occurs on less than one- quarter of any face.
h.Knots . Ensure that knots are sound and tight . Ensure the sum of the least knot dimensions in 6- inch lengths of posts is less than 5 inches. Ensure that the grain distortion caused by knot clusters is no greater than 2½ inches . Ensure that knots do not exceed 2½ inches in the least dimension.
2.MDOT Grade GRB. Provide MDOT Grade GRB guardrail blocks meeting the requirements of this subsection.
a.Splits . Ensure that splits are no greater than 3 inches on the bolt hole plane and no greater than 5 inches in other locations. MDOT Standard Specifications for Construction Section 912 9-110 b. Checks. Ensure that single checks are no greater than 3 inches deep. Ensure that checks opposite each other do not have a total depth greater than 3 inches as measured with a probe no greater than 1/16 inch thick and 1/16 inch in diameter. Ensure that single checks at least ⅜ inch wide as measured at the widest point do not extend along more than one-third of the post length. Ensure that single checks, as measured at the widest point, are no greater than ⅜ inch wide.
c.Shakes. Ensure that shakes are no greater than 3 inches in the smallest dimension and do not extend more than one- half of the standard grading length.
d.Splits, Checks, and Shakes. Ensure that splits, checks, and shakes do not appear in combinations that may cause blocks to separate into pieces.
e.Stains . Ensure that pieces do not contain more than 25 % stained heartwood, and staining is not caused by decay.
f.Wane . Ensure that wane occurs on less than one-third of any face.
g.Knots . Ensure that grain distortion caused by knot clusters is no greater than 4 inches . Ensure that knots do not exceed 4 inches in the smallest dimension.
B.General Requirements
1.Decay . Provide posts and blocks free from decay before treatment.
2.Crook or Bow . Ensure that crooks or bows are no greater than 1 inch per 10 feet of length.
3.Dimensional Tolerances. Provide posts and blocks with the following dimensional tolerances:
a.Cross-section within –½ of the required dimension;
b.Block length within –½ of the required length; and
c.Post length within –2 inches of the required length.
C.Incising . Incise Douglas -fir, western hemlock, and w estern larch timber posts before treatment to meet penetration and retention requirements . Incising blocks is not required. Ensure that the incisor has teeth a nominal ⅞ inch long to make cuts spaced 2½ inches apart lengthwise in rows ¾ inch apart . Ensure that alternate rows are staggered by 1¼ inches to MDOT Standard Specifications for Construction Section 912 9-111 provide 60 diamond patterns of incisions per square foot . Ensure that the diamonds are 2½ inches long and 1½ inches wide from center to center . As an alternative, the Contractor may incise posts in accordance with the American Railway Engineering and Maintenance-of -Way Association ’s Manual for Railway Engineering, Article 3.6.2.
D.Inspection Before Treatment . Inspect air dried or kiln dried material for moisture content as specified in subsection 912.09.E and in accordance with AWPA M2 . Test representative pieces . Test at least 5% or 50 pieces out of a charge, whichever is less.
E.Test for Moisture Content . Test moisture content us ing an electrical resistance type moisture meter with insulated needles 1½ inches long. Correct readings for species and temperature readings in accordance with meter instructions . Take readings on one surface at mid length. Drive needles to their full len gth during readings . The Engineer will accept lots with average moisture content no greater than 19% . Remove individual pieces with moisture contents greater than 23 %.
F.Preservative Treatment . Treat wood for guardrail posts and sign posts in accordance with AWPA U1, Section 6, Commodity Specification A, Use Category 4B . Treat wood for guardrail blocks in accordance with AWPA U1, Section 6, Commodity Specification A, Use Category 4A.
G.Preservatives. Provide preservatives meeting the requirements of AWPA U1, Section 4, “Preservatives for Pressure Treatment Processes, ” and the relevant P Standards.
H.Sorting and Spacing . Provide charges of the same species or species within any one group specified in Tabl e 912-7 . Provide material with a similar moisture content and similar form and size. The Contractor may treat blocks and posts in the same charge after meeting the retention requirements specified in subsection 912.09.K . Use horizontal spacers to separate pieces in the charge to ensure that preservative and steam contact all horizontal surfaces. Table 912- 7: Species Groupings for Treatment in Same Charge Group Group Species A Southern pine B Douglas -fir, balsam fir, eastern h emlock, tamarack C Jack pine, r ed pine, and eastern white pine D Hardwoods MDOT Standard Specifications for Construction Section 912 9-112 I. Conditioning . Use air seasoning, kiln drying, Boulton drying, vapor drying, steaming, or heating in preservative. Ensure average moisture content no greater than 19 % for air seasoned or kiln-dried material before treatment. If steam conditioning, do not exceed the maximum temperature specified in Table 912- 8 in less than 1 hour . If applying a vacuum after steaming, ensure that the vacuum pressure is at least 22 inches of mercury . If using Chromated Copper Arsenate (CCA), Ammoniacal Copper Arsenate (ACA), or Ammoniacal Co pper Zinc Arsenate (ACZA), remove the material from the cylinder and allow it to cool to no greater than 120°F after steaming and before applying the preservative . When treating Douglas -fir with pentachlorophenol, do not steam . If treating southern pine, jack pine, and red pine with CCA, ACA , or ACZA, use steam only to thaw frozen or ice coated material. If conditioning material by heating in preservativ e, ensure that the solution covers the material . Refer to Table 912-8 for maximum temperatures . Do not condition by heating in water borne preservatives, including CCA, ACA, and ACZA. Table 912- 8: Conditioning Methods and Temperature Requirements for Method Used Species Conditioning Methods Allowed Steaming Heating in Preservative Max. Temp (°F) Max. Duration (hour) Max. Temp (°F) Max. Duration (hour) Hard maple Air drying only, no steaming — — — — Other hardwoods(a) (b) — — 220 No limit Southern pine (b) 245 17 220 No limit Eastern white pine (b) 240 4½ 210 6(c) Other softwoods(d) (b) 240 6 210 6(c)
a.Red oak, white ash, white-heartwood beech, yellow birch, hickory, and r ed maple.
b.See subsection 912.08.I.
c.If using seasoned material ; otherwise no limit.
d.Jack pine, Douglas -fir, and red pine, balsam fir, eastern hemlock, tamarack
J.Treatment . Ensure that treatment meets the retentions and penetrations specified in subsection 912.08.K and subsection 912.08.L. Apply pressure in accordance with Table 912- 9. Maintain pressure until the required volume of preservative enters the wood. MDOT Standard Specifications for Construction Section 912 9-113 For pentachlorophenol in Type A hydrocarbon solvent, do not exceed 210°F during the pressure period. For ACA, do not exceed 150°F during the pressure period. For CCA, do not exceed 120°F during the pressure period. For ACZA do not exceed 150°F during the pressure period. If treating with pentachlorophenol, the Contractor may apply an expansion bath or a final steaming after completion of the pressure phase of the treatment, as specified in Table 912- 9. Table 912- 9: Pressure Requirements by Species Species Pressure (psi) Preservative : Pentachlorophenol in Type A Hydrocarbon Solvent Min. Max. Expansion Bath Max . Temp (°F) Final Steaming(a) Max. Temp (°F) Max. Duration (hour ) Red oak 125 250 Not permitted 240 1 Other hardwoods 125 200 Not permitted 240 1 Jack pine, r ed pine 75 175 220 240 2 Southern pine 75 200 220 240 2 Douglas -fir Balsam fir Eastern hemlock Tamarack 50 150 220 240 2 Eastern white pine 50 135 220 240 1
a.If using seasoned material, the Contractor may post -steam at 225°F for no greater than 15 h ours.
K.Retention . Use chemical assay with samples taken after treatment as specified in subsection 912.09.M, and refer to Table 912-10 to determine the minimum retention for the outer 0.6 inch of guardrail posts, blocks, and sign posts using the specified AWPA standards . If treating blocks with posts, determine charge retention by assay of borings from posts.
L.Penetration. Refer to Table 912-11 for heartwood and sapwood penetration requirements . Take samples to determine penetration after treatment as specified in subsection 912.09.M. MDOT Standard Specifications for Construction Section 912 9-114 Table 912- 10: Minimum Retention Requirements Preservative Minimum Retention (pcf) AWPA Standard Guardrail Posts Sign Posts Blocks Pentachlorophenol 0.60 0.50 0.40 A6 CCA, ACZA 0.60 0.50 0.40 A11 ACQ(a) 0.60 Not allowed 0.40 A11 CA-B(a) 0.31 Not allowed 0.21 A11 CA-A(a) 0.31 Not allowed 0.15 A11 Other waterborne preservatives AWPA Commodity Specification A, Table 3.0, Use Category 4B Not allowed AWPA Commodity Specification A, Table 3.0, Use Category 4A A11 Notes: ACQ = ammoniacal copper quaternary ACZA = ammoniacal copper zinc arsenate CA = copper azole CCA = chromated copper arsenate
a.Non-metallic washers or spacers are required for timber and lumber treated with ACQ or CA placed in direct contact with aluminum . Do not use with sign posts. Table 912- 11: Penetration Requirements : Posts and Blocks All Species Allowed(a) Minimum Penetration Heartwood Sapwood Guardrail posts and blocks 0.3 inch 0.6 in ch or 90%, whichever is greater Sign posts 0.5 inch 0.6 in ch or 90%, whichever is greater
a.For red oak, penetrate 65 % of the total annual rings . If red oak cannot be penetrated as required, the Contractor may properly condition wood to refusal.
M.Inspection After Treatment . After treatment, examine the charge for cleanliness, mechanical damage, treatment damage such as severe checking, splitting, or honeycombing and for untreated areas resulting from air pockets, floating material, or insufficient preservative height . Remove defective material before shi pment. The Department will sample material in accordance with MTM 713 and test for preservative retention and penetration.
N.Branding . Permane ntly and clearly burn brand posts and blocks on one wide face. On guardrail posts, ensure that the brand is within 1 foot of the post top. On sign posts, ensure that the brand is within the middle MDOT Standard Specifications for Construction Section 912 9-115 one-third of the post . Ensure that the brand shows the following information in accordance with AWPA M6:
1.Treater ID ;
2.Plant designation;
3.Year of treatment (the month may be included) ;
4.Species or group (code designation specified in Table 912- 12);
5.Preservative type ; and
6.Retention type. Table 912- 12: Group Coding as an Alternative to Species Coding Group Code(a) Hardwoods MH Jack pine J Other softwoods MS Southern pine SP Douglas -fir DF
a.Species designated in Table 912 -4, Table 912 -5, and Table 912- 6.
O.Conformance . Ensure that the treatment plant supplying the material provides a certificate indicating the species, grade, preservative type, retention, year, and name of treater.
P.Degradation After Treatment . Guardrail posts or blocks that develop at least one of the following before installation will be rejected :
1.Single checks at least 3 inches deep or checks opposite each other with a total depth greater than 3 inches as measured with a probe no greater than 1/16 inch thick;
2.Single checks at least ¼ inch wide as measured at the wides t point and extending along more than one-third of the length of the post or block;
3.Single checks greater than ⅜ inch wide as measured at the widest point;
4.Splits in the bolt hole plane greater than 3 inches long;
5.Crooks or bows greater than 1 inch per 10 foot length;
6.Twists; or MDOT Standard Specifications for Construction Section 912 9-116 7. A combination of checks, splits, or shakes that may cause the post or block to separate into pieces.
Q.Guardrail Offset Blocks. The Contractor may select alternat ive materials for guardrail offset blocks from the Qualified Products Li st.
912.09 Timber for Rustic Construction
A.Species and Grade. Provide sound unfinished eastern or northern white pine, red pine, ponderosa pine, D ouglas -fir, northern white cedar, or southern pine for logs, posts, timbers, lumber , and split rails for rustic construction. Provide material free of decay with the bark removed. The Contractor may use salvaged rails from existing rail fences if the salvaged rails are sound and uniform in straightness and size.
B.Shape and Dimensions . Provide logs and posts with an average diameter, at the small end, of no less than the required diameter – ¼ inch.
C.Preservative Treatment . Condition and pressure-treat wood for rustic construction in accordance with AWPA U1, Section 6, Commodity Specificati on B, Use Category 4A (UC4A) , for above ground or Use Category 4B (UC4B) for ground contact.
D.Preservatives. Provide preservatives meeting the requirements of AWPA U1 Section 4, “Preservatives for Pressure Treatment Processes, ” and the relevant P Standards.
912.10 Timber and Lumber for Human Conveyances
A.Preservative Treatment . Provide preservative treatment for timber and lumber on areas where frequent human contact may occur, including deck surfaces, walkways, handrails, steps, railing and fence posts, tables, and benches, with ammoniacal copper quaternary (ACQ) or copper azole (CA), in accordance w ith AWPA U1 -20. Ensure that the ACQ preservative meets the requirements of AWPA P5. Do not use chromium copper arsenate (CCA) or other arsenic -based preservatives. Ensure that the lumber and timber meet the preservative retention and penetration requirements of AWPA U1-20, Table 3.0 and Table 4.0, UC4A for aboveground and UC4B for ground contact. For UC4A, ensure a retention of at least 0.40 . For UC4B, ensure a retention of at least 0.60. Do not use wood species cited in Table 3.0 as “NR (Not Recommended) for ACQ preservative. ”
B.Results of Treatment . Evaluate treatment results, including preservative analysis and penetration and retention, by testing chemical assay, in MDOT Standard Specifications for Construction Section 912 9-117 accordance with AWPA A11. Process and treat wood in accordance with AWPA T1 -04. Ensure that the preservative temperature during the pressure period does not exceed 150°F.
C.Fasteners. For wood treated with ACQ preservative, use stainless steel fasteners or hot -dip galvanized fasteners in accordance with ASTM A653/A653M, batch or post -dipped process, with a coating thickness of at least 1.85 ounces of zinc per square foot of surface area (G185) . Do not mix fastener types . Ensure that aluminum d oes not directly contact ACQ -treated wood. Use non- metallic spacers if contact with aluminum may occur . Do not use aluminum fasteners.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 908–927 of 1,146.