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Why Wood (FAQ)

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Treatment during engineered wood product manufacture

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Some engineered wood panel products, such as plywood and laminated veneer lumber (LVL) are able to be treated after manufacture with preservative solutions, whereas thin strand based products (OSB, OSL) and small particulate and fibre-based panels (particleboard, MDF) are not. The preservatives must be added to the wood elements before they are bonded together, either as a spray on, mist or powder.

Products such as OSB are manufactured from small, thin strands of wood. Powdered preservatives can be mixed in with the strands and resins during the blending process just prior to mat forming and pressing. Zinc borate is commonly used in this application. By adding preservatives to the manufacturing process it’s possible to obtain uniform treatment throughout the thickness of the product.

In North America, plywood is normally protected against decay and termites by pressure treatment processes. However, in other parts of the world insecticides are often formulated with adhesives to protect plywood against termites.

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Buildings

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Wall Types for Water Control

Building envelope experts generally speak of three or four different approaches to design of a wall for moisture control. Face seal walls are designed to achieve water tightness and air tightness at the face of the cladding. An example would be stucco applied directly to sheathing or masonry without a moisture barrier membrane such as building paper. Joints in the cladding and interfaces with other wall components are sealed to provide continuity. The exterior face of the cladding is the primary – and only – drainage path. There is no moisture control redundancy, i.e., there is no back-up system. A face seal system must be constructed and maintained in perfect condition to effectively control rain water intrusion. In general, these walls are only recommended in low risk situations, such as wall areas under deep overhangs or in dry climates. Concealed barrier walls are designed with an acceptance that some water may pass beyond the surface of the cladding. These walls incorporate a drainage plane within the wall assembly, as a second line of defense against rain water.

The face of the cladding remains the primary drainage path, but secondary drainage is accomplished within the wall. This drainage plane consists of a membrane such as building paper, which carries water down and out of the wall assembly. An example is siding or stucco applied over building paper. Concealed barrier walls are appropriate in areas of low to moderate exposure to rain and wind. Rainscreen walls take water management one step further by incorporating a cavity between the back of the cladding and the building paper. This airspace ventilates the back of the cladding, helping it to dry out. The cavity also acts as a capillary break between cladding and building paper, thereby keeping most water from making contact with the building paper. An example of a rainscreen wall is stucco or siding applied to vertical strapping over the building paper. Rainscreen walls are appropriate in high rain and wind exposures. An advancement of the rainscreen technology is the pressure-equalized rainscreen. These walls use vents to equalize the pressure between the exterior and the cavity air, thereby removing one of the driving forces for water penetration (when it is pushed through cracks due to high pressure on the face of the wall and low pressure in the cavity). These walls are for very high risk exposures.

Importance of an Overhang

In a rainy climate, an overhang is one of the simplest and most effective ways to reduce the risk of water intrusion. An overhang is an umbrella for the wall, and the deeper the better. A survey of leaky buildings in British Columbia commissioned by Canada Mortgage and Housing Corporation in 1996 showed a strong inverse correlation between depth of overhang and percent of walls with problems. However, even a small overhang can help protect the wall, largely due to its effect on driving rain. One important benefit of overhangs and peaked roofs often not appreciated is the effect of these elements on wind pressure. Wind-driven rain is typically the largest source of moisture for walls. An overhang and/or sloped roof will help direct the wind up and over the building, which reduces the pressure on the wall and thereby reduces the force of the driving rain striking the wall. This means water is less likely to be pushed by wind through cracks in the wall.

Minimize the Holes

Most rainwater problems are due to water leaking into the wall through holes. If care isn’t taken to protect discontinuities in the envelope, water can leak around window framing and dryer vents, at intersections like balconies and parapets, and at building paper joints, for example. Good design detailing and careful construction is critical! So is maintenance of short-life sealants like caulk around window frames. BC Housing-Homeowner Protection Office has updated the “Best Practice Guide for Wood-Frame Envelopes in the Coastal Climate of British Columbia” originally developed by Canada Mortgage and Housing Corporation and published “Building Enclosure Design Guide for Wood-Frame Multi-Unit Residential Buildings” with extensive information on design and construction detailing.

Use our Effective R calculator to determine not only the thermal resistance of walls, but also a durability assessment of the wall based on representative climate conditions across Canada.

Related Publications

For on-line design and construction tips, try the following:The Build a Better Home program, operated by APA-The Engineered Wood Association, runs training courses, operates a demonstration houses, and offers publications. The web site offers construction information and provides links to all relevant APA publications.

Building Enclosure Design Guide: Wood-Frame Multi-Unit Residential Buildings.

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Environmental Issues

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Safe Handling

Using common sense and standard safety equipment (personal protection and wood-working machinery) applies when working with any building products. Gloves, dust masks and goggles are appropriate for use with all woodworking. Here are a few key points specific to treated wood:

Pressure-treated wood is not a pesticide, and it is not a hazardous product. In most municipalities, you may dispose of treated wood by ordinary garbage collection. However, you should check with your local regulations.
Never burn treated wood because toxic chemicals may be produced as part of the smoke and ashes.
If preservatives or sawdust accumulate on clothes, launder before reuse. Wash your work clothes separately from other household clothing.
Treated wood used for patios, decks and walkways should be free of surface preservative residues.
Treated wood should not be used for compost heaps where free organic acids produced early in the composting process can remove the fixed chemicals. It is, however, safe to use for growing vegetables in raised soil beds. If, after reading this, you are still concerned, place a layer of plastic sheet between the soil and the treated wood wall.
Treated wood should not be cleaned with harsh reducing agents since these can also remove the fixed chemicals.

Environmental Concerns

All wood preservatives used in the U.S. and Canada are registered and regularly re-examined for safety by the U.S. Environmental Protection Agency and Health Canada’s Pest Management and Regulatory Agency, respectively.

Wood preservation is not an exact science, due to the biological – and therefore variable and unpredictable – nature of both wood and the organisms that destroy it. Wood scientists are trying to understand more about how wood decays to ensure that durability is achieved through smart design and construction choices where possible, so that as a society we can be selective in our use of preservatives.

Comparing treated wood to alternative products

A series of life cycle assessments has been completed comparing preservative treated wood to alternative products. In most cases, the treated wood products had lower environmental impacts.

Click for consumer safety information on handling treated wood (Canada).

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Durability Applications

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Article

About Treated Wood

Articles

When you want to use wood that is not naturally decay resistant in a wet application (outdoors, for example) or where it may be at risk for insect attack, you need to specify preservative-treated wood. This is lumber that has been chemically treated to make it unattractive to fungi and other pests. In the same way that you would specify galvanized steel where it would be at risk of rusting, you specify treated wood where it will be used in a setting conducive to decay.

Wood does not deteriorate just because it gets wet. When wood breaks down, it is because an organism is eating it as food. Preservatives work by making the food source inedible to these organisms.

Properly preservative-treated wood can have 5 to 10 times the service life of untreated wood. This extension of life saves the equivalent of 12.5% of Canada’s annual log harvest.

Preserved wood is used most often for railroad ties, utility poles, marine piles, decks, fences and other outdoor applications. Various treatment methods and types of chemicals are available, depending on the attributes required in the particular application and the level of protection needed.

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Additional sources of information

Articles

Links on Durability of Wood Products

Content

On-Line Information on Wood Design and Durability Information On Treated Wood

Information On Termites and Other Pests Information on Mould / Mold

Other Web Sites of Interest Books On Wood Design

ON-LINE INFORMATION ON WOOD DESIGN AND DURABILITY

Canadian Wood Council

Ottawa, Ontario, Canada

The Canadian Wood Council (CWC) is the national association representing Canadian manufacturers of wood products used in construction. CWC participates in building codes and standards committees relating to structural performance, fire safety and durability to ensure proper use of wood products. Designers, builders and building officials address their questions on the design and use of wood products and building systems to CWC’s technical staff, and CWC publishes a large array of manuals, brochures and electronic tools to provide guidance and resource material.

Web site: https://cwc.ca/

Helpdesk: (800) 463-5091

General: (613) 747-5544

Offers: Design handbooks, software, seminars, fact sheets, links and help. Almost everything is available on-line; some books need to be ordered. Information generally aimed at architects and engineers.

Canada Mortgage and Housing Corporation

Ottawa, Ontario, Canada

As Canada’s national housing agency, provides a wide range of services including leading-edge research. CMHC is Canada’s largest publisher of housing information and has Canada’s most comprehensive selection of information about homes and housing.

Web site: http://www.cmhc-schl.gc.ca/en/index.cfm

General calls, in Canada: (800) 668-2642

General calls, from outside Canada: (613) 748-2003

Offers: Best practice guidelines and other publications. Information aimed at the general public as well as designers and builders. Publications must be ordered, either by phone or on-line. On the web site, go to “order desk” to browse catalog and/or purchase on-line. See sub-sections on Design and Construction, Renovation, Healthy Housing and Multi-unit Design for titles of interest. Recommended: “Best Practice Guide, Wood Frame Envelopes in the Coastal Climate of British Columbia” which will be found at Order Desk/Multi-unit Design. CMHC also publishes a two-volume set “Building Envelope Rehabilitation: Consultant Guide and Owner/Property Manager Guide” which provides help in assessing and fixing moisture-related damage in occupied buildings. CMHC’s web site additionally provides quite a bit of information on-line, in brief web pages – from the home page, go to “browse by topic” and click on “building, renovating and maintaining.”

University of Massachusetts, Building Materials and Wood Technology

Amherst, Massachusetts, USA

This web site for a university program primarily contains curriculum information, however click “publications” for plain-language information on many construction topics of general interest.

Web site: http://www.umass.edu/bmatwt/

Offers: Dozens of on-line articles aimed at the general public as well as designers and builders.

US Forest Products Laboratory

Madison, Wisconsin, USA

Established in 1910 by the U.S. Department of Agriculture Forest Service, the Forest Products Laboratory (FPL) serves the public as the U.S.’s leading wood research institute. FPL is recognized both nationally and internationally as an unbiased technical authority on wood science and use. Today, more than 250 scientists and support staff conduct research on expanded and diverse aspects of wood use. Research concentrates on pulp and paper products, housing and structural uses of wood, wood preservation, wood and fungi identification, and finishing and restoration of wood products.

Web site: http://www.fpl.fs.fed.us/

Phone: 608-231-9200

Offers: In addition to information about the research programs and technical research reports, the FPL web site also offers many on-line documents targeted for the general public. From the home page, click “FAQs” for access to the on-line (but somewhat technical) “Wood Handbook.” Click “Techlines” for a series of fact sheets that range from consumer-friendly to fairly technical. FPL is known as a source of information on wood finishes – click “Painting and Finishing Fact Sheets.” Almost all other FPL documents are also available on line. To find reports, papers or other documents, click “Search” (under Publications) on the home page and enter the topic of interest.

American Wood Council (AWC)

Washington, DC, USA

AWC is the wood products division of the American Forest & Paper Association (AF&PA). AWC’s mission is to increase the use of wood by assuring the broad regulatory acceptance of wood products, developing design tools and guidelines for wood construction, and influencing the development of public policies affecting the use of wood products.

Web site: http://www.awc.org/

Helpdesk: (202) 463-4713

General: (202) 463-2766

Offers: Has a very useful helpdesk for any questions regarding the use of wood and its products in building construction. Many publications are available online. Offer technical information regarding U.S. Codes and standards as well as a section on “Mold and Moisture in Homes.”

APA — The Engineered Wood Association

Tacoma, Washington, USA

A membership organization representing 75 percent of the structural wood panel products manufactured in North America, plus a host of engineered products that include glued laminated timber (glulam), composite panels, wood I-joists, and laminated veneer lumber. Very active in research and technology transfer.

Web site: http://www.apawood.org/

Tel: (253) 565-6600

Email: help@apawood.org

Offers: Hundreds of reports, fact sheets and other publications, generally geared for design and construction professionals. Many are available on-line; others can be purchased for a modest fee – search by topic area under “Publications.” Alternatively, browse the site by topic area for a wide range of information, on both specific engineered wood products (click “Products”) as well as general wood framing (click “Applications”). These topic-area pages are nicely cross-referenced to related publications. For specific durability-related information, click “Build a better home” in the left side menu. The web site also has FAQs and a “help desk.” Send questions by e-mail, or phone and ask for the help desk.

National Association of Home Builders Research Center

Upper Marlboro, Maryland, USA

Founded in 1964, the NAHB Research Center is a separately incorporated, wholly-owned, not-for-profit subsidiary of the U.S. National Association of Home Builders (NAHB), a membership organization of builders, manufacturers, and other housing industry professionals. Research spans a broad spectrum including design and construction of homes, land use, the environment, affordable and sustainable housing, and special needs housing. Technology transfer to builders and others is largely via “Toolbase,” a web site supplying information on building products, materials, new technologies, business management, and housing systems.

Web site: http://www.nahbrc.org/

Tel: (301) 249-4000

Toll Free in the US: (800) 638-8556

Toolbase help hotline: (800) 898-2842 (US only)

Offers: The Research Center web site offers 100 publication titles available for purchase, not available on- line. However, click on “Toolbase” and jump to a content-heavy web site with fact sheets, news and more all available on-line. Also has an “ask the expert” feature, by phone or e-mail.

Homeowner Protection Office

Vancouver, British Columbia, Canada

The Homeowner Protection Office (HPO) is a British Columbia Crown corporation formed in 1998 as a response to concerns about the quality of condominium construction in BC. Its purpose is to help strengthen consumer protection for buyers of new homes and improve the quality of residential construction in the province. The HPO is responsible for residential builder licensing, regulating mandatory third-party home warranty insurance, administering a no-interest repair loan program and tax relief grant for owners of leaky homes, and a research and education function designed to benefit the residential construction industry and consumers

Web site: http://www.hpo.bc.ca/

Tel: (800) 407-7757 (BC only)

Offers: This web site is full of on-line information specific to builder and consumer issues in BC. However, click on FAQs or Publications for access to several on-line documents of general interest to anyone involved in moisture-related damage repair.

National Research Council / Institute for Research in Construction (IRC)

Ottawa, Ontario, Canada

Established in 1947, IRC provides research, building code development, and materials evaluation services within Canada’s national laboratory. IRC’s Building Envelope and Structure program develops and applies technologies for design, construction and operation of durable, energy-efficient, and cost-effective building systems, in both new construction and repair or renovation, for all types of buildings. An interesting recent project is the Consortium for Moisture Management for Exterior Walls (MEWS), a research effort addressing some of the technical fundamentals behind moisture performance of building envelopes and funded by a partnership of industry groups. Results, when available, can be viewed on the web site.

Web site: http://www.nrc.ca/irc/bes/index.html

Offers: Click “publications” for access to a rich collection of on-line information, including nearly all of the famous (and not necessarily outdated) Canadian Building Digest articles published between 1960 and 1990. Also available on-line is IRC’s quarterly newsletter, staff articles from construction journals, and more. Some publications are abstracted only and can be ordered.

INFORMATION ON TREATED WOOD

American Wood Preservers’ Association

The American Wood-Preservers’ Association (AWPA) is an international, non-profit technical organization founded in 1904 to provide a common forum for the exchange of information for all segments of the wood preservation industry. AWPA provides standards development and a link for technical exchange between industry, researchers, and users of treated wood. As the principal standards writing organization for the wood treating industry in the United States, AWPA has significant influence internationally as well. AWPA Standards are written to insure that treated wood products perform satisfactorily for their intended uses. The Standards are recognized and used by customers worldwide, who purchase and use treated wood for applications in the building products, electrical, marine, railroad transportation, and road construction industries. The Standards, as well as technical papers contained in proceedings from annual meetings, are available for order through the web site, but may not be viewed on-line. However, there are several fact sheets and FAQs available on-line. Most of AWPA’s information is targeted to the wood treatment industry, but some material may be of interest to treated wood users.

Web site: http://www.awpa.com/

The Wood Preservation Science Council

Cambridge, Massachusetts, USA

Web site provides a thorough collection of on-line research documents (prepared by a variety of agencies) on the subject of health and environmental impacts of CCA-treated wood.

Web site: http://www.woodpreservativescience.org/facts.shtml

Wood Preservation Canada

Ottawa, Ontario, Canada

Wood Preservation Canada is a non-profit industry association comprising members from across Canada. Operating under a Federal Charter, the Institute serves as a forum for those involved with the wood preservation industry, from research to production, marketing and protection of the environment. WPC members cooperate with government departments and other agencies in preparing standards for the industry, and in developing guidelines for the design and operation of wood preservation facilities. It works with Canadian university testing laboratories, faculties and independent research organizations concerned with the development of treated wood. The web site offers many on-line fact sheets and FAQs targeted at users of treated wood. Also available on-line is a table of CSA O80 standards by commodity.

Web site: http://www.woodpreservation.ca/

International Research Group on Wood Preservation

The International Research Group on Wood Preservation (IRG) was launched as an independent research group in January 1969, with the Secretariat currently located in Sweden. Today the Group has more than 300 members from 49 countries around the world. IRG provides a forum and networking system for wood preservation researchers, publishes more than 100 documents every year, arranges conferences and so forth. The web site does not offer any publications on line, however titles can be browsed and ordered through the site. Information offered is highly technical.

Web site: http://www.irg-wp.com/

Western Wood Preservers Institute

Vancouver, Washington, USA

Established in 1950 and representing the interest of the pressure treating wood products industry throughout western North America, WWPI provides a range of information on its web site for users of treated wood.

Web site: http://www.wwpinstitute.org/

INFORMATION ON TERMITES AND OTHER PESTS

Louisiana State University Agricultural Center

Web site: http://www.lsuagcenter.com/en/environment/insects/Termites/

University of Toronto, Urban Entomology Group

Web site offers information on biology and control of termites

Web site: http://www.utoronto.ca/forest/termite/termite.htm

University of Hawaii

Web site: www2.ctahr.hawaii.edu/oc/freepubs/index.asp

Click on “Household and Structural Pests” for fact sheets on termites and on termite barrier technologies.

University of Nebraska, Lincoln

Web site: http://www.ianr.unl.edu/ Search for “termite”.

Australian Pest Controllers Association

Web site: http://www.termite.com/

Very thorough information for builders and homeowners – useful outside Australia as well.

INFORMATION ON MOLD

Mold, Housing and Wood

Written by an industrial hygienist and a wood mycologist in 2002. This 15-page paper is clear and well- referenced. Available on-line: http://www.wwpa.org/lumberandmold.htm

The Condominium Home Owners Guide to Mold

A small booklet published by Canada Mortgage and Housing Corporation, providing useful and simple tips on prevention and cleanup. Available by phone – see CMHC listing at top of page.

Clean-up Procedures for Mold in Houses

Booklet published in 1993 by Canada Mortgage and Housing Corporation. Available from CMHC web site (Order Desk/Healthy Housing). See CMHC listing at top of page.

Mold in Housing: An Information Kit for First Nations Communities

Authored by Canada Mortgage and Housing Corporation, Health Canada and Indian and Northern Affairs Canada. Useful for anyone, not just First Nations/Native Americans. Addresses what to do about mold, in layperson’s language. Available only by phone from CMHC – see listing at top of page.

Fungal Contamination in Public Buildings: A Guide to Recognition and Management

Published by Health Canada in 1995, this 88-page, thorough and scientific report provides a protocol for investigating buildings with suspected fungal problems affecting human health. Available on-line at http://www.hc-sc.gc.ca/ewh-semt/alt_formats/hecs-sesc/pdf/pubs/air/fungal-fongique/fungal-fongique_e.pdf

Guidelines on Assessment and Remediation of Fungi in Indoor Environments Published in 2000 by the New York City Department of Health, Bureau of Environmental and Occupational Disease Epidemiology. Covers health issues and provides a protocol for assessment and remediation. Similar in scientific approach to the Health Canada document, however much shorter. Available on-line at http://home2.nyc.gov/html/doh/html/epi/moldrpt1.shtml

Moulds: Isolation, Cultivation, Identification

An on-line book, 1997, by David Malloch, Department of Botany, University of Toronto:

http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Moulds.html

Mold Resources

The United States Environmental Protection Agency web site has comprehensive on-line information and many links on molds, cleanup and health: http://www.epa.gov/iaq/molds/index.html

Report of the Microbial Growth Task Force

Published by the American Industrial Hygiene Association, 66 pages, 2001, covers procedures for remediation of molds in buildings. Available on-line at: http://www.aiha.org/content/accessinfo/consumer/factsaboutmold.htm

OTHER WEB SITES OF INTEREST

University of Waterloo, Building Engineering Group

Waterloo, Ontario, Canada

The Building Engineering Group (BEG) is a multi-disciplinary group which undertakes research, development and demonstration (R,D & D) for the building industry. BEG is a non-profit, non-proprietary organization operating within the Civil Engineering Department. Operates an outdoor test facility for assessment of building envelope performance, the BEG hut.

Web site: http://www.civil.uwaterloo.ca/beg

Centre for Building Studies, Concordia University

Montreal, Quebec, Canada

The Centre is a research group within the Department of Building, Civil & Environmental Engineering. Research areas include building envelope performance, indoor environment, wind effects and more. The Centre has many advanced facilities for research – click on “Laboratories” to learn more.

Web site: http://www.bcee.concordia.ca/index.php/Centre_for_Building_Studiesindex.htm

National Building Envelope Council

Ottawa, Ontario, Canada

A forum for Canadian design professionals to share information and jointly pursue excellence in design, construction and performance of envelopes. Arranges annual conferences. Local chapters offer regular meetings, lectures, newsletters and so forth – click “Regional BECs”

Web site: http://www.nbec.net/

BOOKS ON WOOD DESIGN

Best Practice Guide, Wood Frame Envelopes in the Coastal Climate of British Columbia. Canada Mortgage and Housing Corporation, 1998. 211p, detailed drawings and 3D PowerPoint files. This is a comprehensive design guide. Also includes some background information on wood decay. Available from CMHC – see listing at top of page.

Building Envelope Rehabilitation: Consultant Guide and Owner/Property Manager Guide. Canada Mortgage and Housing Corporation, 2001. A two-volume set providing help in assessment and remediation of moisture-related damage in occupied buildings. Available from CMHC – see listing at top of page.

Builder’s Guides. J. Lstiburek, 1997, Building Science Corporation, Westford, MA, 303p. http://www.buildingscience.com/, 978-589-5100. Comprehensive guides available in four versions (one each addressing four different climate zones that cover all of North America) with detailed drawings covering design principles, foundations, framing, HVAC, plumbing, electrical, drywall and painting. Building science translated for the builder.

CSA S478-95 Guideline on Durability in Buildings. 1995, 93p, Canadian Standards Association, Etobicoke, ON. Advice on incorporating requirements for durability into the design, operation and maintenance provisions for buildings and their components. Overview of deterioration agents and life expectancies for various components.

Design of Wood Structures for Permanence. Anon., 1988, 17p, American Forest and Paper Association, Washington, DC. A very brief overview of general recommendations on good construction practice.

Available through the web site of the American Wood Council (see above, under “wood design and durability”).

Evaluation, Maintenance and Upgrading of Wood Structures, A guide and Commentary. Subcommittee of American Society of Civil Engineers, 1982, 428p, American Society of Civil Engineers, New York, NY. A somewhat dated guide to the technical aspects of inspection, evaluation, reinforcement, repair and rehabilitation of timber structures. Application of lessons learned to design and maintenance of new structures.

Guide to the Inspection of Existing Homes for Wood-Inhabiting Fungi and Insects. M.P. Levy, 1979, 104p, US Department of Housing and Urban Development. A well illustrated booklet which would be invaluable to anyone inspecting buildings for decay. Not as comprehensive as the BRE publication (see “Recognizing Wood Rot ” below), but more relevant to North American conditions.

Introduction to Wood Building Technology. Canadian Wood Council, 1997, 430p, Ottawa, ON. A technical book on wood-frame construction, it covers materials and properties, thermal insulation, fire protection, construction details, sound control and inspection and repair. Available from CWC – see listing at top of page.

Moisture Control Handbook: New low-rise, Residential Construction. J. Lstiburek and J. Carmody, 1991, 247p, US Department of Commerce, National Technical Information Service, Springfield VA. A guide for heating, cooling and mixed climates. How walls get wet through vapour diffusion, air leakage, condensation, and water leakage. Moisture control strategies. Building science explained.

National Building Code of Canada. National Research Council, 1995, 571p, Ottawa, ON. Minimum requirements to satisfy consumer health, safety and accessibility requirements of buildings. Protection of property is not considered a root objective of the building code consequently references to durability requirements are extremely limited. Very little guidance on how to implement the requirements of the code in terms of moisture control, compared to for example, fire control.

Recognising Wood Rot and Insect Damage in Buildings. A.F. Bravery, R.W. Berry, J.K. Carey and D.E. Cooper, Building Research Establishment, Garston, UK, 1992, 120p. A comprehensive and well-illustrated guide to distinguishing different types of wood-destroying organisms. More relevant to the UK and European building practice and organisms than to North America. Available at http://web.archive.org/web/20051104025920/http://www.bre.co.uk/ (click “bookshop”).

Selection and Use of Preservative Treated Wood. D.L. Cassens, W.C. Feist, B.R. Johnson and R.C. DeGroot, 1995, Forest Products Society, Madison, WI. An excellent guidebook for those contemplating using treated wood in a project.

Wood as a Building Material. W. Wilcox, E. Botsai, and H. Kubler, John Wiley & Sons Inc., 1991. 215 p, index, bibliography, many illustrations. Clear and concise, intended to be readable by building designers. Covers the properties and structure of wood, the relationship between wood and water, wood products, thermal properties, fire performance, decay and its prevention, wood finishing, design guidelines and wood identification.

Wood Protection Guidelines: Protecting Wood From Decay Fungi and Termites. Anon., 1993, Wood Protection Council, National Institute of Building Sciences. A very useful guidebook on controlling the conditions that favour attack by wood-destroying organisms.

Wood Reference Handbook, A Guide to the Architectural Use of Wood in Building Construction. Canadian Wood Council, 2000, 562p, Ottawa, ON. A wealth of basic information on wood characteristics, wood product properties, connections, structural wood systems, building completion, wood finishes, and fire safety. Minimal information on preservative treatment compared to fire control. Available from the Canadian Wood Council – see listing at top of page.

Finishes for Exterior Wood. R. Williams, U.S. Forest Products Laboratory, 1996. Excellent booklet available at low cost, by phone only – see the FPL listing near top of page. Also see FPL web site for on-line fact sheets on finishes.

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EPDs (Demo)

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Environmental product declarations (EPDs)

Stakeholders within the building design and construction community are increasingly being asked to include information in their decision-making processes that take into consideration potential environmental impacts. These stakeholders and interested parties expect unbiased product information that is consistent with current best practices and based on objective scientific analysis. In the future, building product purchasing decisions will likely require the type of environmental information provided by environmental product declarations (EPDs). In addition, green building rating systems, including LEED®, Green Globes™ and BREEAM®, recognize the value of EPDs for the assessment of potential environmental impacts of building products.

EPDs are concise, standardized, and third-party verified reports that describe the environmental performance of a product or a service. EPDs are able to identify and quantify the potential environmental impacts of a product or service throughout the various stages of its life cycle (resource extraction or harvest, processing, manufacturing, transportation, use, and end-of-life). EPDs, also known as Type III environmental product declarations, provide quantified environmental data using predetermined parameters that are based on internationally standardized approaches. EPDs for building products can help architects, designers, specifiers, and other purchasers better understand a product’s potential environmental impacts and sustainability attributes.

An EPD is a disclosure by a company or industry to make public the environmental data related to one or more of its products. EPDs are intended to help purchasers better understand a product’s environmental attributes in order for specifiers to make more informed decisions selecting products. The function of EPDs are somewhat analogous to nutrition labels on food packaging; their purpose is to clearly communicate, to the user, environmental data about products in a standardized format.

EPDs are information carriers that are intended to be a simple and user-friendly mechanism to disclose potential environmental impact information about a product within the marketplace. EPDs do not rank products or compare products to baselines or benchmarks. An EPD does not indicate whether or not certain environmental performance criteria have been met and does not address social and economic impacts of construction products.

Data reported in an EPD is collected using life cycle assessment (LCA), an internationally standardized scientific methodology. LCAs involve compiling an inventory of relevant energy and material inputs and environmental releases, and evaluating their potential impacts. It is also possible for EPDs to convey additional environmental information about a product that is outside the scope of LCA.

EPDs are primarily intended for business-to-business communication, although they can also be used for business-to-consumer communication. EPDs are developed based on the results of a life cycle assessment (LCA) study and must be compliant with the relevant product category rules (PCR), which are developed by a registered program operator. The PCR establishes the specific rules, requirements and guidelines for conducting an LCA and developing an EPD for one or more product categories.

The North American wood products industry has developed several industry wide EPDs, applicable to all the wood product manufacturers located across North America. These industry wide EPDs have obtained third-party verification from the Underwriters Laboratories Environment (ULE), an independent certification body. North American wood product EPDs provide industry average data for the following environmental metrics:

Global warming potential;
Acidification potential;
Eutrophication potential;
Ozone depletion potential;
Smog potential;
Primary energy consumption;
Material resources consumption; and
Non-hazardous waste generation.

Industry wide EPDs for wood products are business-to-business EPDs, covering a cradle-to-gate scope; from raw material harvest until the finished product is ready to leave the manufacturing facility. Due to the multitude of uses for wood products, the potential environmental impacts related to the delivery of the product to the customer, the use of the product, and the eventual end-of-life processes are excluded from the analysis.

For further information, refer to the following resources:

ISO 21930 Sustainability in buildings and civil engineering works – Core rules for environmental product declarations of construction products and services

ISO 14025 Environmental labels and declarations – Type III environmental declarations – Principles and procedures

ISO/TS 14027 Environmental labels and declarations – Development of product category rules

ISO 14040 Environmental management – Life cycle assessment – Principles and framework

ISO 14044 Environmental management – Life cycle assessment – Requirements and guidelines

American Wood Council

Canada Green Building Council

Green Globes

BREEAM®

Annual Review Rules and Form EPD

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Codes and Standards

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The treated wood you buy at your local building supplies store will have an end tag to help you choose the right product. The tag identifies the type of preservative used, the amount retained, the appropriate use for this piece of wood, and the treatment plant name and location. The most important information to look for is the use class. If the piece is going in the ground (e.g. a fence post), you need the piece to be treated for “ground contact.” All other uses (such as fence boards, deck boards and shingles) can be labeled “above ground.” The piece may also be tagged with consumer safety information. You might also find this information in the store, either posted or as a technical brochure.

The National Building Code of Canada (NBC) contains requirements regarding the use of treated wood in buildings and the CSA O80 Series of standards is referenced in the NBC and in provincial building codes for the specification of preservative treatment of a broad range of wood products used in different applications. The first edition of CSA O80 was published in 1954, with eleven subsequent revisions and updates to the standard, with the most recent edition published in 2015.

The manufacture and application of wood preservatives are governed by the CSA O80 Series of standards. These consensus-based standards indicate the wood species that may be treated, the allowable preservatives and the retention and penetration of preservative in the wood that must be achieved for the use category or application. The CSA O80 Series of standards also specifies requirements related to the fire retardance of wood through chemical treatment using both pressure and thermal impregnation of wood. The overarching subjects covered in the CSA O80 Series of standards also include materials and their analysis, pressure and thermal impregnation procedures, and fabrication and installation.

Canadian standards for wood preservation are based on the American Wood Protection Association (AWPA) standards, modified for Canadian conditions. Only wood preservatives registered by the Canadian Pest Management Regulatory Agency are listed.

The required preservative penetrations and loadings (retentions) vary according to the exposure conditions a product is likely to encounter during its service life. Each type of preservative has distinct advantages and the preservative used should be determined by the end use of the material.

Processing and treating requirements in the CSA O80 Series are designed to assess the exposure conditions which pressure treated wood will be subjected to during the service life of a product. The level of protection required is determined by hazard exposure (e.g., climatic conditions, direct ground contact or exposure to salt water), the expectations of the installed product (e.g., level of structural integrity throughout the service life) and the potential costs of repair or replacement over the life cycle.

The technical requirements of CSA O80 are organized in the Use Category System (UCS). The UCS is designed to facilitate selection of the appropriate wood species, preservative, penetration, and retention (loading) by the specifier and user of treated wood by more accurately matching the species, preservative, penetration, and retention for typical moisture conditions and wood biodeterioration agents to the intended end use.

The CSA O80.1 Standard specifies the following Use Categories (UC) for treated wood used in construction:

UC1 covers treated wood used in dry interior construction;
UC2 covers treated wood and wood-based materials used in dry interior construction that are not in contact with the ground but can be exposed to dampness;
UC3 covers treated wood used in exterior construction that is not in ground contact;
- UC3.1 covers exterior, above ground construction with coated wood products and rapid run off of water;
- UC3.2 covers exterior, above ground construction with uncoated wood products or poor run off of water;
UC4 covers treated wood used in exterior construction that is in ground or freshwater contact;
- UC4.1 covers non-critical components;
- UC4.2 covers critical structural components or components that are difficult to replace;
UC5A covers treated wood used in Coastal waters including; brackish water, salt water and adjacent mud zone.

This CSA O80 Series of standards consists of the following standards, as follows:

CSA O80.0 General requirements for wood preservation; specifies requirements and provides information applicable to the entire series of standards.
CSA O80.1 Specification of treated wood; is intended to help specifiers and users of treated wood products identify appropriate requirements for preservatives for various wood products and end use environments.
CSA O80.2 Processing and treatment; specifies minimum requirements and process limitations for treating wood products.
CSA O80.3 Preservative formulations; specifies requirements for preservatives not referenced elsewhere.
CSA O80.4 has been withdrawn.
CSA O80.5 CCA Additives — Utility Poles; specifies requirements for preparation and use of CCA preservative/additive combinations for utility poles permitted by CSA O80.1 and CSA O80.2.

For further information, refer to the following resources:

www.durable-wood.com

CSA O80 Wood preservation

Wood Preservation Canada

National Building Code of Canada

Pest Management Regulatory Agency

American Wood Protection Association

ISO 21887 Durability of wood and wood-based products — Use classes

Click here for more information on performance tests done with treated wood.

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Canadian Preservation Industry

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Canada has had a wood preservation industry for about 100 years. Canada is tied with the UK as the world’s second largest producer of treated wood (the USA is first, by a large margin). In 1999, the most recent year for which we have data, Canada produced 3.5 million cubic metres of treated wood. There are about 65 treating plants in Canada.

As with most other industrialized countries, Canada developed a wood preservation industry using creosote, initially to service railroads (the ties holding the rails) and then utilities (power poles). Creosote production began declining by the 1950s, and by the 1970s was being somewhat replaced for these traditional uses by pentachlorophenol. Today, these oil-borne preservatives only constitute 17% of Canadian treated wood production.

The remaining 83% of production uses water-borne preservatives such as CCA, ACQ and CA. The industry began its substantial shift to the water-borne products in the 1970s, as consumer interest in decks and other residential outdoor structures dramatically increased. For many years, CCA was by far the dominant preservative for both residential and industrial applications.

In 2004, CCA regulations were changed such that CCA is no longer available for many residential applications. Subsequently, Canadian treaters have shifted about 80% of their previous CCA production to ACQ or CA.

Most of Canada’s treated wood is used domestically; Canada exports only 10% of its production.

Canada has its own wood preservation standards, supports several technical and marketing organizations, and maintains a lead position in certain areas of wood preservation research. A major focus of the industry has been in response to increasing levels of health and environmental protection regulations.

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Durability Research and Development

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FPInnovations has been field testing the performance of treated wood products for years. Click one of these categories for performance data from our field tests.

Borate-treated Wood vs. Termites

Naturally Durable Species

The heartwood of species reported to have some natural durability was evaluated in ground contact (stakes) and above-ground (decking) tests.

Commodity: 2×4 and 2×6 lumber from naturally durable species: Western redcedar, yellow cypress, eastern white cedar, larch, tamarack, Douglas-fir

Control species: Ponderosa pine sapwood

Test method: Stake test (AWPA E7) and Decking test (AWPA E25)

Test sites: FPInnovations – Maple Ridge, BC; Petawawa, ON

Michigan Technological University – Gainesville, Florida; Kipuka, Hawaii

Date of installation: 2004-2005

Estimated service life: In the ground-contact stake test, after 5 years moderate to high levels of decay were found in all species at all sites. Yellow cypress and western redcedar were the most durable at all site. Eastern white cedar had similar durability at the Canadian and Florida sites, but was less durable in Hawaii. There were no major performance differences observed between old-growth and second-growth materials used in this study. Untreated naturally durable heartwood is not recommended for long-term performance in ground contact.

In the above ground decking test, at the Canadian test sites after 10 years only small amounts of decay were observed in any of the naturally durable heartwoods tested. In contrast, the ponderosa pine controls had moderate to advanced decay. Decay was more rapid at the Florida and Hawaii test sites, with moderate to advanced decay present in all material types after 7 years. Untreated naturally durable heartwood is not recommended for long-term performance in exposed above ground applications in high decay hazard areas such as Florida and Hawaii. However, in temperate climates these naturally durable heartwoods can provide service lives greater than 10 years.

References:

Morris, P. I., Ingram, J., Larkin, G., & Laks, P. (2011). Field tests of naturally durable species. Forest Products Journal, 61(5), 344-351.

Morris, P. I., Laks, P., Larkin, G., Ingram, J. K., & Stirling, R. (2016). Aboveground decay resistance of selected Canadian softwoods at four test sites after 10 years of exposure. Forest products journal, 66(5), 268-273.

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Wood’s Durable Heritage

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There’s no reason a wood structure can’t last virtually forever – or, at least hundreds of years, far longer than we may actually need the building. With a good understanding of how to protect wood from decay and fire, we can expect today’s wood buildings to be around for as long as we wish.

While wood does not have the historical longevity of stone, there nonetheless remain standing some very old wood buildings. In Europe, wood was long a dominant building material dating back to the beginning of civilisation. Most of these ancient buildings are long gone, lost to fire, decay, or deconstruction for another purpose. In the early days of wood construction, the primary structural components were placed directly in the ground, which eventually leads to decay. It was not until sometime in the 1100s that builders began to use stone footings – thus our still-standing examples of wood buildings generally date from no earlier than that time.

Perhaps the most famous ancient European wood buildings still in evidence today are the Norwegian stave churches, hundreds of which were built in the 12th and 13th centuries and of which 25-30 still remain today. Their exterior claddings have typically been replaced, but the structural wood is original.

The Urnes stave church (c. 1150) in Sogn og Fjordane County is Norway’s oldest. Photo source

In North America, the abundance of wood and the existing timber skills of early settlers led to widespread use of wood – wood has always been and still is the primary structural material for small buildings here. The oldest surviving wood homes in the US date to the early 1600s. Nearly 80 homes remain from this era in the New England states.

The Fairbanks House (c. 1636) in Dedham, Massachusetts, USA, is the oldest surviving timber frame house in North America. It was built for Jonathan and Grace Fairebanke and was occupied by them and seven succeeding generations of the family until the early twentieth century. The Fairbanks family still owns the property. The house is open as a museum. Photo source.

Many other North American wood buildings survive from the 18th century. Even in the demanding climate of Louisiana, where hot and humid conditions present a challenge for wood durability, one can still find some of the original French settlements dating to the first half of the 1700s. And of course, there are countless standing wood buildings from the 1800s and early 1900s, most of which are probably still occupied.

The Parlange Plantation (c. 1750) in Pointe Coupée Parish, Louisiana, USA, was built by the Marquis Vincent de Ternant and remains in the possession of his descendants, the Parlange family. This large plantation home was constructed of bousilliage (mud, moss and deer hair) and cypress wood set over a hand-made brick raised basement. Photo source.

Japan has a well-known history of wood use and is the home of the oldest surviving wood structure in the world, a Buddhist temple near the ancient capital city of Nara. The Horyu-ji temple is believed to have been built at the beginning of the eighth century (c. 711) and possibly even earlier, as one of the hinoki (Japanese cypress) posts appears to have been felled in the year 594. This temple’s longevity is largely helped by careful maintenance and repair. This entire region of Japan has many other ancient wood buildings still standing.

For modern buildings, we don’t normally require such exceptional longevity. The life of a typical North American house is no more than 100 years (the average is lower), and our non-residential buildings are usually demolished in 50 years or less. Wood is perfectly suitable for these lifetime expectations. Click here for survey data showing that wood buildings last as long, or longer than buildings made of other materials.

Reference:
Architecture in Wood: A History of Wood Building and Its Techniques in Europe and North America. Hans Jrgen Hansen, Ed., Faber and Faber, London, 1971..

Case Studies

1865 House, Vancouver BC

Irving House is a large, one and one-half storey plus basement wood-frame residence, designed in the Gothic Revival style, located on its original site at the corner of Royal Avenue and Merivale Street in the New Westminster neighbourhood of Albert Crescent. Irving House is remarkable for the extent to which its original exterior and interior elements have been maintained. Operated as an historic house museum, it also includes a collection of many original furnishings from the Irving family.

Irving House
Location	302 Royal Avenue, New Westminster, B.C.
Completion of Construction	1865
Other Information	Original owner – Captain William and Elizabeth Jane Irving
Current Status	Heritage of New Westminster
Construction Method	Platform-Frame
Style	Gothic Revival style
Framing	2-inch Douglas Fir lumber
Cladding	Wide lapped Redwood weatherboard siding and wooden trim
Comdition	No signs of decay on any framing members
Major Repair	1880

By courtesy of New Westminster Museum and Archives, New Westminster, British Columbia

Other link: http://www.flickr.com/photos/bobkh/297751638/in/set-72157594340707368/

1912 House, Vancouver BC

This classic turn-of-the-century home was slated for demolition in 1990. It was already stripped back to the bare framing when it was purchased by a new owner who wished to convert it into apartments. At the new owner’s request, the building was inspected by Dr. Paul Morris of Forintek in 1991 for signs of deterioration. After 80 years in service there were no signs of decay on any of the framing members nor the window frames, most of which were original.

1912 House
Location	Vancouver
Date of Construction	1912 (estimated)
Original Records	Water service 1909
On City File	1915
Other Information	Original owner – Henry B. Ford
Current Status	Vancouver Heritage Resource Inventory
Construction Method	Platform-Frame
Style	Heritage, with multiple pitched roofs & wide overhangs
Framing	Rough green full 2-inch Douglas Fir lumber
Sheathing	Rough green Douglas Fir boards
Building Paper	Asphalt-impregnated paper
Cladding	Western Red Cedar shakes Western Red Cedar siding
Roofing	Western Red Cedar shakes (new in 1991)
Condition	No signs of decay on any framing members

Temple at Nara, Japan

The Horyuji Buddhist temple at Nara is probably the oldest wooden structure in the world. Nara became the first permanent capital of Japan in 710.

Horyuji Buddhist temple at Nara
Location	Nara, Japan
Date of Construction	670 – 714 (Estimated)
Original Records	Built on site of original temple from 607
Other Information	Original owner – Prince Shotoku
Current Status	World Cultural Heritage Building
Construction Method	Heavy Timber
Style	2-inch Douglas-fir lumber
Framing	Hinoki (Durable – Japanese cypress)
Roofing	Multi-tiered roof with Clay tile
Condition	No signs of decay on any framing members
Maintenance Schedule	Major repairs every 100 years, rebuilt every 300 years

Article

Wood Advantages

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Wood is resistant to some of the chemicals destructive to steel and concrete. For example, wood is often the material of choice when exposed to: organic compounds, hot or cold solutions of acids or neutral salts, dilute acids, industrial stack gases, sea air and high relative humidity. Because of its resistance to chemicals wood is often used in the following applications:

Potash storage buildings
Salt storage domes
Cooling towers
Industrial tanks for various types of chemicals

With thoughtful design and careful workmanship wood bridges prove to be remarkably durable. Throughout the world, there are numerous examples of long lasting wooden bridges – both historic and modern. Modern bridge decks are subjected to relentless attack of de-icing chemicals, and wood is gaining acceptance as a viable option for these applications.

Pilings that are constantly submerged in fresh water have been known to last for centuries. Foundation piles under structures will not decay if the water table remains higher than the pile tops. Many of the world’s important structures are built on wood piles including much of the city of Venice and the Empire State Building in New York.

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Design Faster, Safer, and Better, Today

WoodWorks Software is a must-have tool for structural engineers to quickly design light-frame or heavy timber construction based on the latest codes and standards

Need Support?

The CWC Help Desk offers a number of resources on our Member’s Products to wood professionals and enthusiasts.

Webstore

Why Wood (FAQ)

Wall Types for Water Control

Importance of an Overhang

Minimize the Holes

Safe Handling

Environmental Concerns

Comparing treated wood to alternative products

Links on Durability of Wood Products

Content

ON-LINE INFORMATION ON WOOD DESIGN AND DURABILITY

Canada Mortgage and Housing Corporation

University of Massachusetts, Building Materials and Wood Technology

US Forest Products Laboratory

American Wood Council (AWC)

APA — The Engineered Wood Association

National Association of Home Builders Research Center

Homeowner Protection Office

National Research Council / Institute for Research in Construction (IRC)

American Wood Preservers’ Association

The Wood Preservation Science Council

Wood Preservation Canada

International Research Group on Wood Preservation

Western Wood Preservers Institute

INFORMATION ON TERMITES AND OTHER PESTS

Louisiana State University Agricultural Center

University of Toronto, Urban Entomology Group

University of Hawaii

Australian Pest Controllers Association

INFORMATION ON MOLD

Mold, Housing and Wood

The Condominium Home Owners Guide to Mold

Clean-up Procedures for Mold in Houses

Mold in Housing: An Information Kit for First Nations Communities

Fungal Contamination in Public Buildings: A Guide to Recognition and Management

Moulds: Isolation, Cultivation, Identification

An on-line book, 1997, by David Malloch, Department of Botany, University of Toronto:

Mold Resources

Report of the Microbial Growth Task Force

University of Waterloo, Building Engineering Group

Centre for Building Studies, Concordia University

National Building Envelope Council

BOOKS ON WOOD DESIGN

Environmental product declarations (EPDs)

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