NOTE ** Western Red Cedar Lumber Association, timber construction and landscape structures.
NOTE **
NOTE ** This section is based on Publication 97-508 Revised July 1997, Specifying Western Red Cedar for Timber Construction and Landscape Structures, published by the Western Red Cedar Lumber Association (WRCLA), whose head office is at the following address:
NOTE ** 1100/555 Burrard Street
NOTE ** Vancouver, British Columbia V7X 1S7
NOTE ** Tel: (604) 684-0266
NOTE ** Fax: (604) 682-8641
NOTE ** e-mail: WRCLA@cofiho.cofi.org
NOTE ** Website: www.wrcla.org
NOTE ** Western Red Cedar offers the advantages of natural beauty, design flexibility, exceptional dimensional stability, and long term durability. It is also a recognized structural material with known mechanical and physical properties. These attributes allow the design of timber structures of all types using basic engineering principles and stress- or appearance-rated grades of cedar.
NOTE **
NOTE ** See other WRCLA sections for cedar decking, wood trim, and cedar siding.
NOTE **
NOTE ** SECTION 06139 - TIMBER CONSTRUCTION, Copyright 1998, The Architect's Catalog, Inc.
PART 1 GENERAL
1.1 SECTION INCLUDES
NOTE ** Select paragraphs and subparagraphs below applicable to project; add others as required.
A. Engineered Structures, including:
1. Commercial buildings.
2. Industrial buildings.
3. Residential buildings.
4. ________________________________________.
B. Landscape structures, including:
1. Bridges.
2. Arbors.
3. Pergolas.
4. Gazebos.
5. Field houses.
6. ________________________________________.
C. ________________________________________.
1.2 RELATED SECTIONS
NOTE ** Delete sections below not relevant to this project; add others as required.
A. Section 06100 - Rough Carpentry.
B. Section 06151 - Cedar Decking.
C. Section 06221 - Wood Trim.
D. Section _____ - _________________________.
1.3 REFERENCES
NOTE ** Delete references from the list below that are not actually required by the text of the edited section; add others as required.
A. NLGA/WCLIB - National Lumber Grading Association/West Coast Lumber Inspection Bureau "Grading Standards."
B. __________________________________________.
1.4 DELIVERY, STORAGE, AND HANDLING
A. Inspect the materials upon delivery to assure that specified products have been received.
B. Store materials in safe area, away from construction traffic; store under cover and off ground, protected from moisture.
C. Keep materials clearly separated and identified with grade marks legible. Keep damaged material identified as damaged and stored separately.
PART 2 PRODUCTS
2.1 MANUFACTURERS
A. Acceptable Manufacturer: Member of the Western Red Cedar Lumber Association (WRCLA). ASD.
B. Requests for substitutions will be considered in accordance with provisions of Section 01600.
NOTE ** Delete paragraph above or below; coordinate with Division 1 requirements.
C. Substitutions: Not permitted.
D. Provide all western red cedar from a single supplier.
2.2 MATERIALS
A. Western Red Cedar: WRCLA Western Red Cedar.
NOTE ** Select grade(s), classification(s), surface texture(s), and moisture content of Western Red Cedar from paragraphs below as required for project. Delete references not required for project.
NOTE **
NOTE ** Clear grades have a limited number of natural characteristics and are specified when appearance of the highest quality is required. Clear grades are normally supplied green (unseasoned); when required, seasoning is achieved by air-drying. No. 2 and Better Clear grade should be specified when the finest quality rough lumber is required.
1. Grade: No. 2 and Better Clear.
NOTE ** C and Better Clear is suitable for high-quality landscape structures and as exposed posts and beams in heavy timber construction. WRCLA members produce this grade without cutouts. Available surfaced or rough textured.
2. Grade: C and Better Clear.
NOTE ** D and Better Clear permits larger and more numerous natural characteristics. Some pieces may require trimming to yield clear lengths for the intended use. This grade is widely accepted in the construction of outdoor structures. Available surfaced or rough textured.
3. Grade: D and Better Clear.
NOTE ** Knotty grades present a more rustic appearance, typically supplied green (unseasoned). When required, seasoning is achieved by air-drying.
NOTE **
NOTE ** As a non-structural product, Appearance Knotty grade meets the appearance requirements of quality projects, having highly restricted wane allowances to give well-defined corners. It contains no holes or other characteristics and is available rough sawn or rougher headed in nominal 2 inch and thicker sizes.
4. Grade: Appearance Knotty.
NOTE ** Upon request, Appearance Knotty timbers are available with structural grading. Appearance Knotty, structural, should be specified when strength characteristics are required.
5. Grade: Appearance Knotty, structural.
NOTE ** No. 2 and Better Structural lumber is evaluated for structural strength characteristics, intended for engineered applications where strength is more important than appearance. This grade includes pieces meeting the grades of Select Structural, No. 1 Structural, and No. 2 Structural. Available surfaced or rough textured.
6. Grade: No. 2 and Better Structural.
NOTE ** Standard Beams, Posts, and Timbers are intended for general construction purposes where serviceability is more important than appearance. No structural values are assigned. Available surfaced or rough textured.
7. Grade: Standard Beams, Posts, and Timbers.
NOTE ** Depending upon size, Western Red Cedar is classified as Light Framing, Structural Joists and Planks, Beams and Stringers, or Posts and Timbers.
NOTE **
NOTE ** Light Framing is lumber 2 to 4 inches (50 to 100 mm) thick and 2 to 4 inches (50 to 100 mm) wide, either rough sawn or surfaced four sides (S4S).
8. Classification: Light Framing.
NOTE ** Structural Joists and Planks are rectangular members 2 to 4 inches (50 to 100 mm) thick, 5 inches (125 mm) and wider, either rough sawn or surfaced four sides (S4S).
9. Classification: Structural Joists and Planks.
NOTE ** Beams and Stringers are rectangular members, either rough sawn or surfaced, 5 inches (125 mm) and thicker with width 2 inches (50 mm) greater than thickness.
10. Classification: Beams and Stringers.
NOTE ** Posts and Timbers are square members, either rough sawn or surfaced, 5 inches by 5 inches (125 x 125 mm) and larger with width not more than 2 inches (50 mm) greater than thickness.
11. Classification: Posts and Timbers.
NOTE ** Saw Textured surface, obtained during the milling process using either circular or band saws, is present on all four sides.
12. Surface Texture: Saw Textured.
NOTE ** With Rougher Headed texture, the lumber receives its texture from a milling process which uses roughened planer knives. The rough texture is clearly visible on all four sides.
13. Surface Texture: Rougher Headed.
NOTE ** S4S Texture provides a uniformly sized product and a smooth surface on all four sides for a high quality appearance. Sizes from 2 x 4 up to 6 x 6 are generally available; larger sizes are produced on special orders.
14. Surface Texture: Surfaced Four Sides (S4S).
NOTE ** Select moisture content from the three subparagraphs below. Delete those not required.
15. Moisture Content: Green (unseasoned).
16. Moisture Content: Air-dried.
17. Moisture Content: Kiln-dried, 2 inch (50 mm) thickness only.
B. Fasteners:
NOTE ** Hot-dipped galvanized, aluminum, and stainless steel fasteners can be used to fasten Western Red Cedar. Other types of nails are not recommended as they can rust, disintegrate, and react adversely with the natural preservative oils present in cedar, resulting in stains and streaks. Copper nails also react with cedar and should not be used.
NOTE **
NOTE ** Stainless steel nails are the best choice, especially if the wood is to be finished with transparent or semi-transparent stain. Use No. 304 stainless steel for general applications, No. 316 for seacoast exposures.
NOTE **
NOTE ** Select nail type from subparagraphs below or add other type fasteners. Delete those not required for project.
1. Nails: Hot-dipped galvanized.
2. Nails: Aluminum.
3. Nails: No. 304 stainless steel.
4. Nails: No. 316 stainless steel.
5. _______________________________.
NOTE ** Large members require timber connectors other than nails. Bolts, lag screws, split rings and shear plates, and custom made hardware are commonly used in heavy timber structures where the joint strength must be greater than could be achieved with nails. These types of connectors should be corrosion-resistant or suitably coated to prevent corrosion and staining.
NOTE **
NOTE ** Generally, the design of mechanically fastened joints must consider a variety of factors such as end- and edge-spacing distances, moisture content, service conditions, and the effect of the number of connectors used. Because the cost of fabricating and installing connectors may amount to a large percentage of the cost of a heavy timber structure, it is important to engineer the details of a structure before designing the timber members.
C. Timber Connectors: _______________________________.
PART 3 EXECUTION
3.1 PREPARATION
A. Coordinate work with related trades; scribe and cope timbers for accurate fit. Allow installation of related work to avoid cutting and patching.
B. Select timbers of longest possible lengths. Ensure that knots and obvious defects will not interfere with placing fasteners or making proper connections. Cut out and discard defects that render a piece unfit to serve its intended function.
C. Discard timbers that are warped, twisted, bowed, crooked, or otherwise defective.
3.2 INSTALLATION
A. Install timbers square, plumb, and level, closely fitted and securely fastened.
B. Nail pieces to provide penetration of not less than half nail length into piece receiving nails. However, 16d nails may be used to connect two pieces of nominal 2-inch (50 mm) timbers. Nail without splitting timbers.
3.3 FIELD QUALITY CONTROL
A. Timber construction may be rejected, whether or not installed, for excessive warp, twist, bow, or crook, as well as for improper cutting or fitting.
3.4 ADJUSTING AND CLEANING
A. As work proceeds, maintain premises free of unnecessary accumulation of tools, equipment, surplus materials, and debris related to this work.
