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Preventing dry rot damage

The most important way to prevent dry rot damage is to reduce or eliminate excess moisture. This may be as simple as repairing a leaky pipe or as complicated as stopping water infiltration through a basement foundation. A common cause of dry rot and termite damage is wood in contact with soil as occurs, for example, with a failed foundation.

If moisture cannot be controlled, or if the dry rot fungus as gained a foot-hold, then wood should be treated to inhibit the growth of the fungus (see below). Boric acid, or borate, is an excellent fungicide (a pesticide that kills fungi) against the dry rot fungus. Borate also prevents insect damage. Wood can be treated during construction, during repair, or as a remedial treatment to stop an active infestation.

Borates for structural pests like dry rot are generally applied as liquids with some type of sprayer. However, most forms of ordinary borate should not be used if liquid water is present, such as outdoors, because borates are water soluble and will wash away. In these wet situations use fused borate instead because it is made for exterior applications. Fused borate is often used to protect log ends in log homes (see Protecting Log Homes From Insects and Dry Rot). These cut log ends are subject to attack because moisture and rot can easily start on these exposed surfaces. Fused borate is also widely used to treat wood utility poles against dry rot.

Treating dry rot

Treating dry rot is a three step process. Step 1 is to locate and stop the source of the moisture which caused the problem in the first place. Until the source of the moisture is found nothing productive can be done. Step 2 is to replace any wood that is so damaged that it has become structurally weakened. The services of a qualified carpenter may be need to perform these repairs. Step 3 is to treat new and existing wood with borate to prevent future advance of the dry rot fungus and kill any fungus in the treated wood.

Borate is available as a dry powder or a glycol-based liquid concentrate. The powder form is generally less expensive but there's some evidence that glycol improves the absorption of borate into the wood fibers. One popular liquid borate product that is specifically made to protect wood from dry rot is called Bora Care (see Using Bora Care To Protect Wood From Dry Rot) and one of the powder forms is called TimBor (see Using TimBor to Treat Wood Against Dry Rot).

After mixing with water either product should be applied to dry, unfinished wood with a pump sprayer or paint roller. Some applications require two coats (see label instructions). Neither TimBor nor Bora Care are generally available in stores but can be purchased online at the 'Bugs Store (right).

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