Exposed wood should be checked for signs of rot

July 24, 2006|by GENE GARY / Copley News Service

Q: I am a faithful reader of your column, as a homeowner and a fairly adept handyman. Some time ago, you answered a question on dry rot repair of a window. At the time, I was not in need of this type of information. Since then, we have relocated, purchasing an older home. I have discovered signs of wood rot in some of the exterior window trim. Is it possible for you to send me a copy of your recommendations for repair of this type of damage?

A: That column appeared in September 2004. Since wood rot is a common problem, one on which I get numerous questions, I am happy to repeat the information again.

Dry rot is actually decay of the wood caused by fungus that survives in a moist environment. Wood exposed to continual dampness in warm weather is particularly vulnerable to the invading rot fungi, and it doesn't have to be older wood to be attacked.


Horizontal areas where water doesn't drain well, such as window- and doorsills, are common problem areas, as well as any exposed wood grains, which tend to wick water into the interior of the wood. Joints, which dry slowly, and wood that is close to the ground, concrete or masonry are also prime areas for development of dry rot.

Signs of trouble include paint that is cracked, peeling or blistering, or wood that's darker than the surrounding area or green with algae. Sometimes the fungus is visible. It grows out of the wood surface, appearing as mottled white or brown patches. The wood may be white and spongy or brown and crumbly.

Test suspicious areas by probing the wood with a screwdriver, ice pick or awl. Wood with interior rot may sound hollow, feel spongy and yield easily to the probe. If you can push the tip of the probe easily into a suspect board, then it's time to take action.

There are two ways to deal with rotted wood: replace or repair. Replacement eliminates the rot, but it is expensive and often requires carpentry skills beyond the level of the average do-it-yourselfer. Repairing damaged sections can save money, but if done incorrectly it can actually promote further decay.

If infected wood is not replaced or repaired quickly, the fungus will spread. If the wood is badly damaged and it is impossible to repair with a reasonable amount of work, replacement is the best solution. This is particularly true if the damaged wood is in a location that weakens the entire structure, such as supporting posts for a porch or deck, flooring, beams, joists, etc.

Areas infected with wood rot that have limited structural importance are often good candidates for repair versus replacement. This is particularly true with old houses, for which ornamental wood pieces might be difficult or impossible to match or duplicate and suitable wood-frame windows are not readily available. In such cases, time-consuming efforts required for restoration make sense.

Even if repairs are minor, it is important that as a first step you locate the source of moisture and take steps to eliminate it. Often, doorjambs and windowsills get wet during damp weather, but they should dry thoroughly when the weather is better. If rainwater penetrates cracks in the woodwork and can't drain out, continually wet wood decays or rots from the inside out.

Excessive moisture penetration can also come from condensation and dripping water from roof leaks, gutters and downspouts that are damaged or improperly installed to take water away from the house. Bad drainage at the foundation, moisture collection underneath in the crawl space, minor leaks in plumbing, or even poor ventilation are other sources of moisture problems.

Repairing rotted wood is a tricky procedure. Special wood-patching products that are highly resistant to water must be used. Most wood patching products are two-part epoxy compounds that are mixed immediately before use to the consistency of putty. Once the putty has hardened, it can be worked much like wood - smoothed or shaped with tools such as chisels, rasps and sandpaper.

Before these products can be applied, the wood surface must be properly prepared. Remove loose and decayed wood with a wood chisel. If it is not feasible to scrape away all the rotted wood to a sound wood surface, a consolidant must be used.

A consolidant, usually a liquid, impregnates and reinforces the wood fibers. It strengthens and solidifies the infected wood as it works its way through the structure and bonds with the remaining solid wood. If the wood is damp, be sure to let it dry completely before applying the consolidant or the repair won't work.

To allow the consolidant to penetrate the wood, it is sometimes necessary to drill a honeycomb pattern of holes using a 3/16-inch twist drill bit. Take care not to drill completely through the wood to be treated, or the consolidant will run out. Any accidental holes you make can be plugged with nonhardening clay - the same type used in kindergarten classes and available at art supply and hobby shops.

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