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991

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566.89M

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17,845

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110,845

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Economic Impact Map

The U.S. wood products industry makes products essential to everyday life from a renewable resource.

Click on a state to display employment statistics in the text field to the right.

THE U.S. WOOD PRODUCTS INDUSTRY:

Makes products essential to everyday life from a renewable resource that absorbs and sequesters carbon
Employs almost 465,000 people in wood products manufacturing and supports additional jobs in forestry and other industries
Pays over $2.2 billion in state and local taxes annually

USA Fact Sheet

Download / Print PDF

Hawaii

Alaska

New Jersey

Delaware

Maryland

West Virginia

Florida

Mississippi

Alabama

Georgia

South Carolina

North Carolina

Virginia

Tennessee

Kentucky

Louisiana

Arkansas

Missouri

Texas

Oklahoma

Kansas

New Mexico

Colorado

Arizona

Utah

Nevada

California

Maine

New Hampshire

Vermont

Massachusetts

Rhode Island

Connecticut

New York

Pennsylvania

Ohio

Indiana

Michigan

Illinois

Wisconsin

Iowa

Minnesota

Nebraska

South Dakota

North Dakota

Wyoming

Idaho

Oregon

Washington

WA State Data

Download / Print PDF

EMPLOYMENT

Direct 14,515
Indirect 14,858
Induced 10,122
Total Employment 39,495

COMPENSATION

Direct $1,284,784,927
Indirect $1,302,920,958
Induced $730,849,145
Total $3,318,555,029

INDUSTRY OUTPUT

Value of Production – Direct $7,678,760,807
Value Added – Direct $3,206,192,198

Montana

Code Adoption Map

Applicability Key

Limited/Local

Statewide

Tall Mass Timber Permitted in State or Jurisdiction

The International Code Council (ICC) is the leading developer of model building codes that are adopted for use in the United States.

In some fashion every state has adopted one or more of the codes promulgated by ICC. The exact number of codes, the method of enactment, and their application to buildings varies considerably across the 50 states. This map shows states that have adopted the IBC at a statewide, local, or limited level, and specifies the edition of the code currently being enforced in the state. Because the updating process is dynamic, the information may change and the map may not reflect the most current information. If you feel something is in error, please bring it to our attention at [email protected].

Statewide adoption indicates the code applies to all building construction throughout the state. Local adoption indicates that certain jurisdictions have adopted one or more codes, but the regulation only applies within the legal limits of the jurisdiction. Limited adoption means that one or more state agencies have adopted a code and apply it either to state owned buildings, or buildings that are in some legal manner under the purview of the agency.

Code Adoption Map

Montana

Montana Building Codes Council

Adopted I-Codes:

2021 International Building Code (IBC)

2021 International Residential Code (IRC)

2021 International Energy Conservation Code (IECC)

For a full list of codes used in the state, check the ICC Code Adoption Map.

Applicability (statewide, local, limited): STATEWIDE

The State of Montana Building Codes Council adopts codes for state projects but local cities, counties, etc can adopt a State certified building code.

Tall Mass Timber Adoption

The tall mass timber provisions went into effect in 2023.

Notes:

The adopted code amendments are found in the following link Building Code Amendments | SBCC (wa.gov). The International Existing Building Code is adopted by reference in the Washington State Building Code. The State of Washington adopted ICC codes may be viewed in read only format over the ICC website.

Page last updated: December 2023

Code Adoption Map

Idaho

Idaho Building Code Boards
Department of Building Safety

1090 E. Watertower Street
Meridian, ID 83642
Phone: (208) 334-3951
Contact: Chris Jensen, Administrator, 208-334-3951
https://dbs.idaho.gov/

Adopted I-Codes:

2018 International Building Code (IBC)

2018 International Energy Conservation Code (IECC)

2018 International Residential Code (IRC)

For a full list of codes used in the state, check the ICC Code Adoption Map.

Applicability (statewide, local, limited): STATEWIDE

The IBC, IRC and IEBC are adopted at the State level, local jurisdictions can amend. Local jurisdictions cannot adopt amendments that are more restrictive than the State codes with the exception of Chapter 11 which cannot be less restrictive. The enabling legislation does not allow one and two family dwellings to be required to have automatic sprinklers.

Here is a summary for code applicability: https://dbs.idaho.gov/faqs/building-frequently-asked-questions/

Tall Mass Timber Adoption

The tall mass timber provisions went into effect in 2021.

Notes:

Page last updated: December 2023

A list of lumber grading rules writing organizations certified by the American Lumber Standards Committee (ALSC) is provided below.

NELMA. Standard Grading Rules for Northeastern Lumber; published by the Northeast Lumber Manufacturers Association (NELMA), 272 Tuttle Road, P.O. Box 87A, Cumberland Center, ME 04021; 207.829.6901; 207.829.4293 (fax); e-mail [email protected]
RIS. Standard Specifications for Grades of California Redwood Lumber; published by the Redwood Inspection Service (RIS), 1500 SW First Avenue, Portland Oregon 97204-2122; 503.224.3930; 503.224.3934 (fax); e-mail [email protected]
SPIB. Standard Grading Rules for Southern Pine; published by the Southern Pine Inspection Bureau (SPIB), 4555 Spanish Trail, Pensacola, FL 32504; 850.434.2611; 850.434.1290 (fax); e-mail [email protected]
PLIB/WCLIB. Standard Grading Rules for West Coast Lumber; published by the Pacific Lumber Inspection Bureau (PLIB/WCLIB); 1010 South 336th Street, Suite 210, Federal Way, WA 98003; 253.835.3344; 253.835.3371 (fax); e-mail [email protected]
WWPA. Western Lumber Grading Rules; published by Western Wood Products Association (WWPA); 1500 SW First Avenue, Portland Oregon 97204-2122; 503.224.3930; 503.224.3934 (fax); e-mail [email protected]
NLGA. Standard Grading Rules for Canadian Lumber; published by the National Lumber Grades Authority (NLGA); Suite 303 – 409 Granville St., Vancouver, BC V6C 1T2; 604.673.9100; 604.673.9141; e-mail [email protected]

For the most up to date information see:
https://www.alsc.org/untreated_graderuleorg_mod.htm

A list of lumber grading rules writing organizations certified by the American Lumber Standards Committee (ALSC) is provided below.

NELMA. Standard Grading Rules for Northeastern Lumber; published by the Northeast Lumber Manufacturers Association (NELMA), 272 Tuttle Road, P.O. Box 87A, Cumberland Center, ME 04021; 207.829.6901; 207.829.4293 (fax); e-mail [email protected]
RIS. Standard Specifications for Grades of California Redwood Lumber; published by the Redwood Inspection Service (RIS), 1500 SW First Avenue, Portland Oregon 97204-2122; 503.224.3930; 503.224.3934 (fax); e-mail [email protected]
SPIB. Standard Grading Rules for Southern Pine; published by the Southern Pine Inspection Bureau (SPIB), 4555 Spanish Trail, Pensacola, FL 32504; 850.434.2611; 850.434.1290 (fax); e-mail [email protected]
PLIB/WCLIB. Standard Grading Rules for West Coast Lumber; published by the Pacific Lumber Inspection Bureau (PLIB/WCLIB); 1010 South 336th Street, Suite 210, Federal Way, WA 98003; 253.835.3344; 253.835.3371 (fax); e-mail [email protected]
WWPA. Western Lumber Grading Rules; published by Western Wood Products Association (WWPA); 1500 SW First Avenue, Portland Oregon 97204-2122; 503.224.3930; 503.224.3934 (fax); e-mail [email protected]
NLGA. Standard Grading Rules for Canadian Lumber; published by the National Lumber Grades Authority (NLGA); Suite 303 – 409 Granville St., Vancouver, BC V6C 1T2; 604.673.9100; 604.673.9141; e-mail [email protected]

For the most up to date information see:

https://www.alsc.org/untreated_graderuleorg_mod.htm

Where can I obtain information on designing post frame structures (sometimes referred to as pole buildings or pole barns)?

1. Design values for poles (smaller at the top and buried) and piles (smaller at the bottom and driven) are in the 2005 NDS Chapter 6. Design values for poles and piles were moved to the NDS Supplement: Design Values for Wood Construction in the 2012 Edition.

2. Post-Frame Design Manual (Second Edition) to be published by the Technical & Research Committee of the National Frame Builders Association (NFBA).
NFBA
4840 Bob Billings Parkway
Lawrence, KS 66049-3862
Phone: (800) 557-6957
Local: (785) 843-2444
Fax: (785) 843-7555
E-mail: [email protected]
Website: NFBA (National Frame Building Association)

3. ASAE Post Frame Building Manual
ISBN: 0-929355-29-6
Phone: 800-695-2723
Fax: 269-429-3852

4. The Midwest Plan Service publishes a Structures and Environment Handbookwhich address gussets in section 406.5 under Wood Truss Design. The most recent edition is a 1987 Revised 11th Edition. For ordering information, visit
https://www-mwps.sws.iastate.edu/catalog/construction-farm/structures-and-environment-handbook
Midwest Plan Service
122 Davidson Hall
Iowa State University
Ames, IA 50011-3080
Toll Free: (800) 562-3618
E-mail: [email protected]

Design for Code Acceptance (DCA) #5 provides guidance to post-frame building designers for meeting the requirements of the 2000 International Building Code and to confirm that a properly designed post-frame building is in fact code compliant.

See also General FAQ: “Where can I find information on Timber Poles and Piles?”
See also General FAQ: “What is timber frame construction and where do I find more information about it?”

The sections of the IBC and IRC that deal with sound transmission are IBC Section 1206 and IRC Appendix AK. These code provisions apply to wall and floor/ceiling assemblies separating dwelling units from other dwelling units, or from adjacent public areas, within a building. These provisions do not deal with sound transmission from outdoors to indoors, through an exterior wall. Although US model building codes do not contain provisions regulating minimum sound transmission performance of exterior walls, there are some cases where designers specify a minimum level of sound transmission performance for exterior walls on specific construction projects. In such cases, the most direct and accurate way of assessing sound transmission performance of an exterior wall is through field testing in accordance with ASTM E966 and analysis in accordance with ASTM E1332. The single-number ratings resulting from this test and analysis procedure are outdoor-indoor transmission class (OITC) and outdoor-indoor noise isolation class (OINIC(θ)). Conversely, sound transmission class (STC) is determined through laboratory testing in accordance with ASTM E90 and analysis in accordance with ASTM E413. This testing and analysis is most commonly used for assessing the sound transmission performance of interior walls and floor/ceiling assemblies separating dwelling units from other parts of a building, as these are the only places where US model building codes require minimum sound transmission performance. While it is possible to perform an ASTM E90 test on an exterior wall assembly in a laboratory and determine an STC rating for that assembly using ASTM E413, this is less commonly done because building codes do not place minimum performance requirements on sound transmission through exterior wall assemblies and because OITC and OINIC(θ) ratings provide in-situ assessments of exterior wall performance.

As stated in Section 1.1 of ASTM E90, the scope of this standard is limited to building partitions such as walls, operable partitions, floor-ceiling assemblies, doors, windows, roofs, etc. Although it is possible to use ASTM E90 to assess the sound transmission performance of individual components that would be used within an assembly, such use is not within the scope of the standard and is typically only done for the purpose of research. Furthermore, sound transmission class (STC) values derived for individual components of an assembly are not necessarily additive. In other words “component-additive methods” (CAM) do not necessarily yield accurate estimates of sound transmission through a complete assembly. This is especially the case when dealing with assemblies that have a cavity or void through the thickness (e.g., a stud wall with cavities between the studs). That said, there are other models (besides CAM) for estimating sound transmission performance that yield more accurate results. For example, AWC’s Technical Report 15 (TR15) provides models that can be used to estimate STC and impact-insulation class (IIC) ratings for light-frame floor/ceiling assemblies (https://awc.org/publications/tr-15-calculation-of-sound-transmission-parameters-for-wood-framed-assemblies ).

Rafter spans from the AWC Span Calculator are calculated as maximum horizontal (projected) spans. Snow loads used to calculate the maximum horizontal spans are assumed to be uniform and independent of the snow loading condition (i.e. flat roof versus sloped roof, warm roof versus cold roof, balanced versus unbalanced, etc). The designer first determines the appropriate snow load condition and then he/she can use the AWC Span Calculator to calculate the maximum horizontal span for that loading condition.

ASCE 7 Minimum Design Loads for Buildings and Other Structures contains provisions to determine the loads for specific loading conditions based on adjustments to the ground snow load. The AWC Span Calculator does not have the means to calculate these adjustments, so rather than providing drop-down options for snow loads (e.g. 20 psf, 30 psf, etc.), the AWC Span Calculator requires the roof snow load to be calculated and entered manually.

For roof rafters where the maximum horizontal projected rafter span from eave support to ridge is less than 20 feet, ASCE 7 provides a simplification that sets the unbalanced snow load equal to the ground snow load (see Snow Provisions in ASCE 7-05 for more information) which simplifies the determination of the snow load condition. This simplification also applies in ASCE 7-10.

The provisions of NDS Chapter 16 and FDS Chapter 3 are intended to allow the designer to use analytical methods to establish the fire resistance time associated with a wood member or assembly tested to an ASTM E119 fire exposure. In this mechanics-based design method, wood design properties intended for structural design are adjusted to nominal strengths for fire resistance calculations. These nominal strengths are used with cross-sections, reduced due to charring of the wood, to calculate the time to structural failure of a wood member or assembly. As such, application of the slenderness limits intended to provide safe structural designs to provisions for estimating structural failure time is unnecessary and would reduce accuracy of the estimated failure time. Reference to the equation 3.7-1 is provided within Chapter 16 to remind the user that the stability equations should be applied in the design of columns. Reference to the stability equations like 3.7-1 were only to remind the user that stability equations should be applied, but not intended to require application of design slenderness ratio limitations that are specific to structural design. As stated in NDS Commentary Section C16.1, these provisions do not address procedures for evaluating members for continued service following fire damage.

Design for Code Acceptance (DCA) #1 Flame Spread Performance of Wood Products provides building-code-accepted flame spread ratings for various wood products and species which are normally used as interior finishes for walls, ceilings, and floors in buildings.

Wood materials may be used as an interior finish in almost all occupancies. IBC Table 803.9 indicates the finish classification required for every occupancy and location within the building. The required classifications (A, B, or C) are ranges of flame spread resulting from testing per ASTM E84 or UL723.

Flame spread classification is usually obtained from the manufacturer, but code officials and designers can also make use of DCA 1 to quickly determine the flame spread of lumber and various engineered wood products. Most wood species qualify as Class C, but some can qualify as Class B. All the products listed in DCA 1 also meet the maximum smoke-developed index of 450 required by the building code (803.1.1).

The flame spread index of fire-retardant-treated wood is required to be 25 or less (Class A) per Section 2303.2. Traditional wood floor coverings are exempt from interior finish requirements, and exposed portions of Type IV (Heavy Timber) structural members are also exempt from the interior finish requirements of the code (Section 804).

For occupancies such as stores, apartments, offices, and other commercial and industrial uses, building codes commonly require floor/ceiling and wall assemblies to be fire-resistance-rated in accordance with standard fire tests. The 2012 International Building Code permits fire-resistance-rating to be established by several methods. Testing is the primary means (703.2, 2012 IBC), but not the only one. The five alternatives shown in 703.3 permit the code official to allow fire-resistance-rating to be established using a number of methods and principles of fire resistance in the code and elsewhere:

Fire-resistance-rated designs documented in sources.
Prescriptive designs of fire-resistance-rated building elements, components, or assemblies as prescribed in IBC Section 721.
Calculations in accordance with IBC Section 722.
Engineering analysis based on a comparison of building element, component, or assemblies designs having fire-resistance-ratings as determined by the test procedures set forth in ASTM E 119 or UL 263.
Alternative protection methods as allowed by IBC Section 104.11.

For tested assemblies, AWC’s DCA 3 – Fire-Resistance-Rated Wood Floor and Wall Assemblies describes how interior and exterior wood-frame walls and wood I-joist floors can be used to meet building code requirements for fire-resistance-rated assemblies.

Additional assemblies not shown in DCA 3 can be found in the 2005 ASD/LRFD Manual for Engineered Wood Construction Chapter M16.

Performance of finger-jointed lumber in fire-resistance-rated wall assemblies is also a common question. In 2009 the American Lumber Standards Committee (ALSC) modified the ALSC Glued Lumber Policy to add elevated-temperature performance requirements for end-jointed lumber adhesives intended for use in fire-resistance-rated assemblies. End-jointed lumber manufactured with adhesives which meet the new elevated-temperature requirements is required to be designated as “Heat Resistant Adhesive” or “HRA” on the grade stamp. 2012 IBC Section 2303.1.1.2 on End-Jointed Lumber states, “Approved end-jointed lumber is permitted to be used interchangeably with solid-sawn members of the same species and grade. End-jointed lumber used in an assembly required to have a fire-resistance-rating shall have the designation “Heat Resistant Adhesive” or “HRA” included in its grade mark.”

Designing Retaining Walls, Bulkheads and Seawalls of Treated Timber. Author: American Wood Preservers Institute, 1966
Earth Retaining Structures. Author: W.D. Keeney, AWPI
Improved Standard Designs Pressure-Treated Timber Crib Walls. AWPI, 1969.
Available upon e-mail request: [email protected].

NDS Archives + Historical Design Values

1991-1997 NDS Commentary – Historical Development

Wood Handbook – Wood as an Engineering Material

Wood and Timber Condition Assessment Manual, Second Edition – Electronic (PDF)
by Robert J. Ross and Robert H. White

Here’s contact information for the lead author:
Dr. Robert J. Ross
Email: [email protected]
Phone: (608) 231-9221
Website: http://www.fs.fed.us/research/people/profile.php?alias=rjross

Other resources:

Evaluation, Maintenance and Upgrading of Wood Structures: A Guide and Commentary. Published by: ASCE (Proceedings of a session at Structures Congress, 1986). Edited by: Alan Freas. Available at https://play.google.com/store/books/details?id=6lghAGA7OLwC

Evaluation and Upgrading of Wood Structures: Case Studies. Published by: ASCE (Proceedings of a session at Structures Congress, 1986). Edited by: Vijay K. A. Gopu. Available at http://cedb.asce.org/CEDBsearch/record.jsp?dockey=0050270
ISBN # 0872625508

Grading of existing timbers

West Coast Lumber Inspection Bureau (WCLIB) will grade existing timbers. Here’s contact information:

WEST COAST LUMBER INSPECTION BUREAU
PO Box 23145
Portland, Oregon 97281-3145
503-639-0651
Fax: 503-684-8928
http://www.wclib.org/

Historical Considerations in Evaluating Timber Structures
R. L. Tuomi and R. C. Moody, Engineers
Forest Products Laboratory U.S. Department of Agriculture
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr21.pdf

Fire and Smoke Repair

Restoration Industry Association Guidelines for Fire & Smoke Damage Repair, 2nd Edition

Classic texts online

Rankin, William John MacQuorn (1866): Useful Rules and Tables Relating to Mensuration, Engineering, Structures, and Machines, Charles Griffn and Company, London, UK.
Includes timber design properties (see p. 199).

Johnson, J.B. (1904): The Materials of Construction – A Treatise for Engineers on the Strength of Engineering Materials, Fourth Edition, John Wiley & Sons, New York, USA.
Comprehensive strength of materials text for typical materials of the time, including timber (see p. 236-238).

Ketchum, Milo S. (1918): Structural Engineers Handbook – Data for the Design and Construction of Steel Buildings and Bridges, Second Edition, McGraw-Hill Book Company Inc., New York, USA.
Includes timber Bridges and trestles (see p. 298).

Jacoby, H.S. (1909): Structural Details or Elements of Design in Timber Framing, John Wiley & Sons, NY, USA.
An early authoritative text on timber detailing, joints, connections, design, and more.

The video was published in 1993 by Odyssey Productions, Inc. and was sponsored by WWPA, AF&PA, SFPA, and APA. Contact SFPA (Southern Forest Products Association) at 504-443-4464 or http://www.sfpa.org. Ref #AV45

Floor joist span tables are tabulated based on allowable deflection limits of L/360. Floor live loads range from 30 psf for sleeping areas to 40 psf for other occupancies. Ceiling joist span tables are tabulated based on allowable deflection limits of L/240.

Typically a user will know the span and desired spacing for a given application. The user can select a species, size, and grade for trial use. Using the Design Values for Joists and Rafters, the user determines the modulus of elasticity and bending design value of the species, grade and size of lumber. Bending design values are already adjusted for load duration and repetitive member factors in the Design Values Supplement. With this information the user enters the span table with the given modulus of elasticity and determines the allowable span for an estimated size and spacing. If the allowable span is greater than that required for the application, the species, grade and size selected should then be verified for bending strength. At the bottom of each table, required bending design strengths for specific joist spacing are tabulated. If the bending design value selected from the Design Values Supplement is greater than the tabulated required bending design value, then the species and grade chosen is adequate. If the bending design value is less than the tabulated value then the user can either select a deeper member, decrease the joist spacing or select a higher lumber grade, thus a higher bending design value. For either option, modulus of elasticity has to be re-evaluated to ensure the deflection limits are maintained. Linear interpolation for intermediate design values is permitted.

More details available in the tutorial.

No. An engineer or architect should design cantilever members. Design of cantilever beams involves many variables including load, cantilever span and interior or back span. Often the load is not a single uniform distribution over the length of the member, and other additional loads are present, such as point loads at the end of the member. Because the system is composed of two pieces: the cantilever span, and the back span, the placement and magnitude of load on these sections singly or combined will cause different stresses to develop in the member. The designer seeks to find the worst combination of loading that will impose maximum shear, bending, or deflection in the member.

American Wood Council’s 2001 Wood Frame Construction Manual has engineered and prescriptive provisions that may give guidance for typical cantilever cases. For example, the Engineered Design provisions for sawn lumber floor joists in 2.3.1.6 state the maximum overhang length is limited to the depth of the joist if the end of the cantilever supports a load bearing wall or shear wall (Figure 1, below).

When designed for additional loads, cantilevers are limited to 4 times the depth of the joist (Figure 2, below).

The cantilevered joist must be located directly over studs unless the top plates are designed to carry the loads. If the end of the cantilever supports a non-loadbearing non-shear wall, then the maximum overhang length is limited to one-fourth of the joist span (Figure 3, below).

Consult manufacturer’s recommendations if using I-joists. Prescriptive Design provisions found in 3.3.1.6.1 for sawn lumber floor joists are the same except that for roof live loads and ground snow loads less than or equal to 20 psf and 30 psf, respectively, cantilevers shall not exceed one-eighth of the joist span for lumber joists supporting only a roof with a clear span of 28 feet or less.

A variety of Span Table Documents and Span Calculator products are available for use in wood building design, complete with a tutorial for their use.

The online AWC Span Calculator performs calculations for ALL species and grades of commercially available softwood and hardwood lumber as found in the NDS Supplement. There are also several other online span tables available for various regional species and grades of lumber and loading conditions:

Canadian Span Tables and Calculator
Southern Pine Span Tables
Western Span Tables and Calculator

Rafter span tables are tabulated based on allowable deflection limits of either L/240 or L/180.

The L/240 limitation allows for attachment of a ceiling to the underside of the rafter by limiting possible cracking. Cathedral ceilings are an example of this type of application. The L/180 deflection limitation would apply to a rafter with no ceiling directly attached, so deflection is not a concern.

Roof live and snow loads range from 30 psf to 60 psf. Roof dead loads range from 10 to 20 psf.

Typically a user will know the span and desired spacing for a given application. The user can select a species, size, and grade for trial use. Using the Design Values for Joists and Rafters, the user determines the modulus of elasticity and bending design value of the species, grade and size of lumber. Bending design values are already adjusted for load duration and repetitive member factors in the Design Values Supplement. With this information, the user enters the span table with the given bending design value and determines the allowable span for an estimated size and spacing. If the allowable span is greater than that required for the application, the species, grade and size selected should then be verified for stiffness or deflection. At the bottom of each table required modulus of elasticity for specific joist spacing are tabulated. If the modulus of elasticity is less than the tabulated value then the user can either select a deeper member, decrease the joist spacing or select a high lumber grade, thus a higher modulus of elasticity. For either option, bending design strength has to be re-evaluated to ensure that strength limits are maintained.

Decking Span Tables

Redwood – Click “Deck Construction” to see their updated version
http://www.calredwood.org/literaturelibrary/

Southern Pine
http://www.southernpine.com/span-tables/

Western Red Cedar
http://www.realcedar.com/decking/products/

National Lumber Grades Authority’s rule #126 under all species that have been graded according to NLGA (which includes Ponderosa Pine) for Exterior Patio Decking provides grade rules as follows:

“Exterior patio decking rough or unsurfaced – kiln dried, air dried, or unseasoned 5/4″ to 2″ thicknesses, 4″ and wider for flatwise load applications where spans are not to exceed 16″ on centre.”

Beam load tables in WSDD are tabulated based on spans from 4 to 32 feet and for lumber sizes from 2×4 to 24×24 inches.

Typically a user will know the span and load for a given application. The user can select a species, size, and grade for trial use. Using the Design Values for Wood Construction Supplement, the user determines the modulus of elasticity, bending design value, and shear parallel to grain design value of the species, grade and size of lumber. These design values need to be modified for all applicable adjustment factors including load duration and repetitive member factors from the Design Values Supplement and NDS. With this information the user enters the load table with the given bending design value and determines the allowable load for an estimated size. If the allowable load is greater than that required for the application, the species, grade and size selected should then be verified for stiffness and shear. Below each tabulated load value are the required modulus of elasticity and shear design value for the specific application. If the modulus of elasticity and shear design value selected from the Design Values Supplement is greater than the tabulated required modulus of elasticity and shear value, then the species and grade chosen is adequate. If the modulus of elasticity or shear design value is less than the tabulated value then the user can either select a larger member, or select a higher lumber grade. For either option, bending design strength has to be re-evaluated to ensure that strength limits are maintained. For multiple members or built-up members, the allowable load would be determined by dividing the actual load by the number of plies selected for that particular member. Linear interpolation for intermediate design values is permitted.

Wood Structural Design Data (WSDD) tabulates two different types of column load tables: simple solid columns and spaced columns.

Typically, a user will enter the tables with a known length for the column and a given load. The user can select a species, size, and grade for trial use. Using the Design Values for Wood Construction Supplement, the user determines the modulus of elasticity and compression parallel to grain design value of the species, grade and size of lumber. These design values need to be modified for all applicable adjustment factors including load duration from the Design Values Supplement and NDS. The user should determine the length to depth ratio based on the size of member selected. With this information the user enters the load table with the given modulus of elasticity and compression design value and determines the allowable load for the calculated length to depth ratio. If the allowable load is greater than that required for the application, the species, grade and size selected are adequate. If the allowable load is less than required then the user can either select a larger member, or select a higher lumber grade.

There are no specific provisions for connections for built-up beams. WCD#1, Details for Conventional Wood Frame Construction outlines the following general criteria:

Beams and girders are of solid timber or built-up construction in which multiple pieces of nominal 2-inch thick lumber are nailed together with the wide faces vertical. Such pieces are nailed with two rows of 20d nails-one row near the top edge and the other near the bottom edge. Nails in each row are spaced 32 inches apart. End joints of the nailed lumber should occur over the supporting column or pier. End joints in adjacent pieces should be at least 16 inches apart, Figure 15.

There is a General FAQ dealing with increased buckling capacity for built-up beams:
“Is there a design method for increased buckling capacity of built-up wood beams?”

USDA Forest Products Lab Wood Handbook, Table 4-7 titled “Thermal conductivity of selected hardwoods and softwoods” lists thermal properties for various species of wood. The table is available online as a PDF file at:
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_04.pdf

The Canadian Wood Council has a technical bulletin on the thermal performance of light-frame wood assemblies. It discusses an R value of 1.5/inch of thickness for wood products:
http://www.cwc.ca

Also, from 1993 ASHRAE standard, the R value per inch of thickness is about 1.1 F*ft^2*h/BTU per inch of thickness.

Thermal conductivity is a measure of the rate of heat flow through one unit thickness of a material subjected to a temperature gradient. The thermal conductivity of common structural woods is much less than the conductivity of metals with which wood often is mated in construction. It is about two to four times that of common insulating material. For example, the conductivity of structural softwood lumber at 12% moisture content is in the range of 0.7 to 1.0 Btu×in/(h×ft²×^oF) compared with 1,500 for aluminum, 310 for steel, 6 for concrete, 7 for glass, 5 for plaster, and 0.25 for mineral wool.

In Chapter 4 of the USDA Forest Products Lab Wood Handbook, Table 4-7, entitled “Thermal conductivity of selected hardwoods and softwoods” lists thermal properties for various species of wood.

Thermal expansion/contraction for wood is minimal. The USDA Forest Products Lab Wood Handbook, Chapter 3. Page 3-21 outlines thermal expansion coefficients for wood, which are almost microscopic. Any expansion joint would be based on roofing material requirements.