Editing Lumber (section)

==Durability and service life==
Under proper conditions, wood provides excellent, lasting performance. However, it also faces several potential threats to service life, including fungal activity and insect damage – which can be avoided in numerous ways. Section 2304.11 of the [[International Building Code]] addresses protection against decay and termites. This section provides requirements for non-residential construction applications, such as wood used above ground (e.g., for framing, decks, stairs, etc.), as well as other applications.

There are four recommended methods to protect wood-frame structures against durability hazards and thus provide maximum service life for the building. All require proper design and construction:
* Controlling moisture using design techniques to avoid decay
* Providing effective control of termites and other insects
* Using durable materials such as pressure-treated or naturally durable species of wood where appropriate
* Providing quality assurance during design and construction and throughout the building's service life using appropriate maintenance practices

===Moisture control===
Wood is a [[Hygroscopy|hygroscopic]] material, which means it naturally absorbs and releases water to balance its internal moisture content with the surrounding environment. The moisture content of wood is measured by the weight of water as a percentage of the oven-dry weight of the wood fiber. The key to controlling decay is controlling moisture. Once decay fungi are established, the minimum moisture content for decay to propagate is 22 to 24 percent, so building experts recommend 19 percent as the maximum safe moisture content for untreated wood in service. Water by itself does not harm the wood, but rather, wood with consistently high moisture content enables fungal organisms to grow.

The primary objective when addressing moisture loads is to keep water from entering the building envelope in the first place and to balance the moisture content within the building itself. Moisture control by means of accepted design and construction details is a simple and practical method of protecting a [[Timber framing|wood-frame building]] against decay. For applications with a high risk of staying wet, designers specify durable materials such as naturally decay-resistant species or wood that has been treated with [[preservative]]s. [[Cladding (construction)|Cladding]], [[Shake (shingle)|shingles]], [[sill plate]]s and exposed timbers or [[Glued laminated timber|glulam beams]] are examples of potential applications for treated wood.

===Controlling termites and other insects===
For buildings in termite zones, basic protection practices addressed in current building codes include (but are not limited to) the following:

* Grading the building site away from the foundation to provide proper drainage
* Covering exposed ground in any crawl spaces with 6-mil polyethylene film and maintaining at least {{convert|12|to|18|in}} of clearance between the ground and the bottom of framing members above (12&nbsp;inches to beams or girders, 18&nbsp;inches to joists or plank flooring members)
* Supporting post columns by concrete piers so that there is at least {{convert|6|in}} of clear space between the wood and exposed earth
* Installing wood framing and sheathing in exterior walls at least eight inches above exposed earth; locating siding at least six inches from the finished grade
* Where appropriate, ventilating crawl spaces according to local building codes
* Removing building material scraps from the job site before backfilling.
* If allowed by local regulation, treating the soil around the foundation with an approved termiticide to provide protection against subterranean termites

===Preservatives===
{{Main|Wood preservation}}
[[File:Treated timber.jpg|thumb|upright|Special fasteners are used with treated lumber because of the corrosive chemicals used in its preservation process.]]

To avoid decay and termite infestation, untreated wood is separated from the ground and other sources of moisture. These separations are required by many building codes and are considered necessary to maintain wood elements in permanent structures at a safe moisture content for decay protection. When it is not possible to separate wood from the sources of moisture, designers often rely on preservative-treated wood.<ref>{{cite web|url=http://www.woodworks.org/files/PDF/publications/wood-design-durability-service-life-fact-sheet.pdf|title=WoodWorks Durability and Service Life|access-date=2011-06-01|archive-url=https://web.archive.org/web/20120405185524/http://www.woodworks.org/files/PDF/publications/wood-design-durability-service-life-fact-sheet.pdf|archive-date=2012-04-05|url-status=dead}}</ref>

Wood can be treated with a preservative that improves service life under severe conditions without altering its basic characteristics. It can also be pressure-impregnated with fire-retardant chemicals that improve its performance in a fire.<ref>[https://books.google.com/books?id=0SkDAAAAMBAJ&pg=PA59 "Wood That Fights."] ''Popular Sciences'', March 1944, p. 59.</ref> One of the early treatments to "fireproof lumber", which retard fires, was developed in 1936 by the Protexol Corporation, in which lumber is heavily treated with salt.<ref>[https://books.google.com/books?id=lNsDAAAAMBAJ&pg=PA560 "Lumber is Made Fireproof by Salt Treatment" ''Popular Mechanics'', April 1936] bottom-left p. 560</ref> Wood does not deteriorate simply because it gets wet. When wood breaks down, it is because an organism is eating it. 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. 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.<ref name="About Treated Wood - CWC">{{cite web|title=About Treated Wood|url=http://cwc.ca/design-with-wood/durability/pressure-treated-wood/about-treated-wood/|archive-url=https://web.archive.org/web/20150203121514/http://cwc.ca/design-with-wood/durability/pressure-treated-wood/about-treated-wood/|url-status=dead|archive-date=3 February 2015|website=CWC|access-date=7 May 2017}}</ref>

There are two basic methods of treating: with and without pressure. Non-pressure methods are the application of preservatives by brushing, spraying, or dipping the piece to be treated. Deeper, more thorough penetration is achieved by driving the preservative into the wood cells with pressure. Various combinations of pressure and vacuum are used to force adequate levels of chemical into the wood. Pressure-treating preservatives consist of chemicals carried in a solvent.
Chromated copper arsenate, once the most commonly used wood preservative in North America began being phased out of most residential applications in 2004. Replacing it are amine copper quat and copper azole.

All wood preservatives used in the United States 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.<ref name="About Treated Wood - CWC"/>