A Rot Inspection involves examining all wood members in a home for signs of rot. All wood products used in construction are vulnerable to rot, but if properly maintained they can easily last for hundreds of years. There are three main types of fungi that attack wood: stain, mold and decay (rot).
Wood rot is the result of an attack of the decay fungi, while stain and mold fungi mainly grow on the wood surface, causing discoloration. They do not weaken the wood by themselves, but their presence indicates a moisture problem, thus conditions favorable to the growth of the decay fungi.
Rot Inspection – Decay Fungi Infestation
Decay fungi are microscopic thread-like plants that grow in the wood and attack its cell walls. They eventually break down the walls and feed on the contents of the cells. Once the cells are destroyed, the wood disintegrates and decay becomes obvious.
In the early stages, it may be very difficult to notice that a section of wood has been attacked by the decay fungus. The wood might just be discolored. The advanced stages of decay, however, are easily recognizable because the wood undergoes changes in properties and appearance. Wood affected by decay fungi might be brownish and crumby or white and spongy. In either case, keep in mind that decay can greatly reduce the strength and structural value of the wood member.
Rot Inspection – First Signs of Decay
The brown and crumby rotted sections break into small cubes and are often dry in the final stage of deterioration. Most people refer to this condition as “dry rot”, but the term is not accurate considering that the actual decay occurred when the wood was wet. Decay fungi cannot survive in dry wood.
In some cases, the physical changes in the wood are not visible on the surface, but they can be easily detected by probing the wood with a screwdriver or an ice pick. If the wood is in good condition, the tool will not penetrate much beyond the surface, but if it is deteriorated to probe will easily penetrate into the wood.
Moreover, the conditions that promote growth of decay fungi also promote subterranean termite and carpenter ant infestation. When probing wood members, you may find deteriorated sections caused by a combination of decay and insect damage.
Under suitable conditions of humidity and temperature, the decay fungus gives rise to a fruiting body that contains great numbers of microscopic spores – the seeds of a new generation of decay fungi spores readily distributed by air currents. The spores are always present in the air and cannot be kept away from wood under normal conditions. Unless the moisture content of the wood and the temperature are suitable for spores germination and growth, the presence of decay fungi spores on wood is of no concern.
Decay fungi will grow and develop only when the moisture content of the wood is in excess of 20 percent and the temperature ranges between 40 degrees F and 115 degrees F. Temperatures above the upper limit will kill the decay fungi, while temperatures below the lower limit will cause the fungi to become dormant.
Temperatures below the lower limit is a condition that readily occurs in the northern states during the winter. When the temperature rises in the spring, the decay fungi in infested lumber resumes growth if the moisture content of the wood has not changed.
The decay fungi thrive when the moisture content is about 25 percent, but when the wood is saturated with moisture the lack of oxygen will inhibit them from growing. The moisture content of green lumber can be as high as 200 percent, but after the lumber has been kiln-dried its moisture content may drop as low as seven to ten percent.
If a house has been properly constructed and maintained, the wood within the house will seldom have a moisture content over 15 percent. On the other hand, if the moisture content exceeds 20 percent, the wood becomes vulnerable to deterioration by decay fungi.
Any wood that is subjected to damp or wet conditions should be treated with toxic chemicals in order to prevent decay. If possible, a better solution may be using heartwood of certain species such as cypress, redwood or cedar for those sections to be subjected to damp or wet conditions, because these species of wood are resistant to rot. To avoid problems with decay fungi, schedule a Rot Inspection before the contract closes.