508Timber Structures

Timber Structures

Description

508.01This work consists of the construction of timber structures and timber portions of other

structures per these specifications and in conformity with the lines and grades shown on the plans or established.

Materials

508.02Sawn lumber and timber shall conform to AASHTO M 168. Timber shall be Douglas Fir of

the coast region or Southern Yellow Pine. “Native” timber may be used when noted on the plans. “Native” timber shall be Red Cedar, Douglas Fir of the inland region, Lodgepole Pine, Ponderosa Pine, Spruce, as listed and described in AASHTO M 168, or any other native wood specifically approved for the intended purpose. All timber shall be of the grade or shall meet the working stresses shown on the plans. Timber used in non-structural applications, whose working stresses are not shown on the plans, shall be graded to produce a working stress of 1,000 pounds per square inch on the extreme fibers when subjected to bending and 800 pounds per square inch when subjected to compression parallel to the grain. Material of equal or greater stress values may be used. All lumber shall be manufactured per Product Standard 20-70 as published by the Department of Commerce and shall be grade-marked by a grading agency or have an accompanying certificate from a grading agency. The grading agency shall be certified by the Board of Review of the American Lumber Standards Committee.

508.03Treated Timber. The preservative to be used shall be as specified on the plans. The

preservatives and entire treatment process shall be as described in AASHTO M 133 or by the American Wood Protection Association (AWPA) standards.

508.04Inspection. All timber furnished shall be covered by a certificate of inspection issued

by the American Lumber Standard Committee (ALSC) or the International Accreditation Service

Shop drawings shall be submitted per subsection 105.02 for all major structures and for other structures when specified.

The Department may provide an inspector at the treating plant for material quality review and inspection of the treatment process for treated timber. The plant shall notify the Engineer sufficiently in advance of time of treating so that inspection may be arranged.

508.05Hardware. Hardware shall include all bolts with necessary nuts and washers, timber

connectors, drift pins, dowels, nails, screws, spikes, metal pile protectors, steel anchor plates and all other metal fastenings as shown on the plans. Bolts shall conform to the requirements of boat spikes and other spikes shall be wrought iron or steel. Washers shall be standard cast iron ogee or malleable cast washers. Timber connectors and common nails shall be of the type and size specified on the plans. All hardware, except timber connectors and common nails, shall be galvanized per AASHTO M 232.

508.06

Construction Requirements

508.06Timber for the various portions of the structure shall be treated or untreated as

stipulated on the plans. Treated timbers shall not be sized or trimmed in the field, except when ordered. The Contractor shall not make temporary use of treated timber. All pieces that have been field cut shall be treated per AWPA Standard M4.

Untreated stringer ends shall be separated at least 1/2 inch and shall be secured to the timber where they rest. Sway bracing shall be securely bolted to piling or post and caps as shown on the plans. Treated filling pieces shall be used in lieu of framing or dapping to bring bracing into a plane. Bulkheads, where required, shall be full size timber. Posts for framed bents shall be of the proper length for their position and provide an even bearing on cap and sill. All untreated caps shall be sized over the piles or posts to a uniform thickness and even bearing on piles or posts. Caps shall be within 1/4 inch of nominal depth before treatment and may be surfaced on the vertical grain face. Before the timber capping is placed, a No. 20 gauge galvanized sheet metal cap shall be placed on each pile per the plans. In lieu of the sheet metal cap, three layers of heavy burlap may be used. Each layer of burlap shall be cut square to a dimension of 12 inches greater than the diameter of the pile head and shall be thoroughly swabbed with hot asphalt. The overhanging ends shall be turned down and secured to the pile with galvanized wire. The entire wrapping shall then be swabbed with a heavy application of hot asphalt.

Longitudinal X-braces shall be properly framed and secured to piles or posts. Truss and bent timbers shall be cut and framed in such manner that they will have even bearing over the entire contact surface of the joint. Blocking or shimming will not be allowed in making joints. Open joints will not be accepted. Stringers shall not be more than 1/4 inch off nominal size, before treatment. Floors shall be constructed as shown on the plans. The plank shall be secured to each stringer with two 7-inch spikes. Half-inch cracks between planks shall be left in plain plank floors without surfacing. Laminated floors shall be secured as shown on the plans.

508.07Holes and Bolts. All holes bored shall be treated per AWPA M4. Holes drilled for

drift bolts shall be 1/32 inch smaller than the diameter of the bolt. All other holes shall be bored to such size as to ensure a snug fit. Unless otherwise designated, all bolts shall be provided with two ogee washers.

508.08Painting. All paint shall conform to the requirements of Section 708. Timber to be

painted shall be surfaced on four sides and shall be cleaned immediately preceding painting. New timber to be painted shall receive one coat of primer. “White Wood Primer” shall be used when the surface is to be finished with “Outside White Paint.” For “Exterior Black Paint,” the specification paint shall be thinned by adding one part linseed oil and one part turpentine to eight parts paint for use as a primer. The surfaces of all untreated timber to be painted shall be primed with one coat of primer immediately after the material is delivered to the project. Unless otherwise designated, pieces shall be primed as specified for the finish coat of paint, or “White Wood Primer” shall be used when additional painting is not required. Untreated timber will not require additional priming.

508.09

All handrails and handrail posts shall be of untreated timber and shall be painted as described hereafter. Contact surfaces shall receive the primer and one coat of paint before placing handrails.

Parts specified, parts shown on the plans, and all exposed non-galvanized iron and steel shall, after the prime coat, be given two coats of the specified paint, which shall be thoroughly brushed in. Paint shall be applied only to thoroughly dry surfaces. All previous coats shall have thoroughly dried before subsequent coats are to be applied. Portions to be painted above the wheel guards or top wales shall be painted white and those portions below the wheel-guards or top wales to be painted shall be painted black.

508.09Structure Number. The location, letters, figures, and paint used for stenciling shall be

per the plan details.

Method of Measurement

508.10Timber will be measured by the thousand feet board measure [MFBM] actually

incorporated in the structure and shall include hardware unless otherwise designated on the plans.

Basis of Payment

508.11The accepted quantities will be paid for at the contract unit price for each of the pay

items listed below that appear in the bid schedule. Payment will be made under: Pay Item Pay Unit Untreated Timber MFBM Treated Timber MFBM

Structure excavation and structure backfill will be measured and paid for per Section 206. Timber piling will be measured and paid for per Section 502.

508.11

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509.01