Wood is one of the most widely used building materials. Because wood is a natural, organic material, it is susceptible to deterioration when exposed to wood-degrading organisms, such as fungi, bacteria, and insects (termites and carpenter ants). Wood decay, or rot, occurs when the environment within the wood becomes hospitable for fungi that feed on the wood’s cellular material.
For wood to be able to sustain high levels of microbial activity, several conditions must be met, including moisture and temperature. Elevated moisture levels (about 20% MC) and temperatures (above 70 degrees Fahrenheit) are required for decay to occur, with significant deterioration occurring when the moisture content of the wood is above its fiber saturation point.
Decay can significantly affect the physical properties of wood, which can, in-turn, become an important concern for wood that is expected to provide structural support. Wood that decays to the point of being structurally compromised can necessitate expensive and intrusive repairs. Often, wood decay on a balcony occurs hidden from plain view, concealed by finishes and floor coverings. The decay may thus progress undetected for a significant period. If framing becomes structurally compromised from rot, costly repair may be needed.
Types of rot and where it can be found
Brown Rot
Brow rot causes the wood to break down into brown cubes that split against the grain. Advanced stages of brown decay result in dry, powdery wood that is unable to support much weight, and crumbles easily.
White Rot
White appears whitish, stringy and mushy, and tends to be more common in hardwoods.
Dry Rot
"Dry Rot" has been used to describe decayed wood that has since dried and ceased decaying. Some people may erroneously assume that the wood is still in the process of decay. Moisture is required for wood decay to occur, so no literal “dry rot” exists.
Likely locations where rot can be found include:
Balconies and decks
Stairs and attachment points to the house in decks
Improperly installed door thresholds, especially beneath sliding glass doors
Roof penetrations with improper or corroded flashing
Beneath windows
Support post bases of decks
Sidewall and headwall locations
Untreated wood in direct contact with concrete, masonry, or soil
How to Prevent Wood Decay
If the decay hazard is high, such as might be the case for an exterior elevated element (balcony, stairs, landings), select the heartwood of decay-resistant species, such as redwood or cedar, or use wood properly treated with preservative.
When standard sawn lumber (or engineered wood) is used for framing purposes, a properly-instilled waterproofing system is needed to protect from water infiltration. Though there are many waterproofing systems available, quality of installation is key.
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