Wood decay is caused by wood-rotting fungi that grow in damp wood. Fungi attack wood members in contact with damp masonry foundations, moist ground or standing water, and water pipes on which moisture condenses. Poor ventilation around the wood hastens the process of decay.
Wood decay is indicated by the following:
A damp, musty odor
Opening or crumbling of the wood
The presence of fine, dusty, reddish-brown powder under the building
A hollow sound when the timber is tapped
Easy penetration of timber by a sharp-pointed tool
Corrective actions taken to alleviate wood decay include the following:
Removal of fungus-infested lumber. Spray infested areas with wood preservative.
Elimination of the source of moisture. Add fill around masonry and grade swales to lead water away from the foundation. Where land contours do not promote runoff, install drain tiles around the foundation and lead them to a storm drain, or provide a dry well at a lower elevation than the water table at the foundation.
Provision of ventilation to affected areas.
Replacement of infested lumber with lumber treated with wood preservative.
An inspection should include a check, where applicable, for termites. Wood and wood-and- masonry members are susceptible to termite attack. Subterranean termites become established in wood that is in contact with moist soil. Their presence may be indicated by earthlike shelter tubes leading from the ground to the infested wood. Dry-wood termites live all their lives in dry, sound, and seasoned wood. A reliable sign of dry-wood termite attack is the finding of pellets in the immediate area. Among basic methods of preventing termite infestation are soil treatment, use of wood preservatives (such as pentachlorophenol), removal of surplus wood and other debris from the site, preventing contact of lumber with the ground, and covering openings into attic spaces with suitable hardware cloth or copper screening.
In crawl spaces or "dead" areas under non basement structures, moisture control problems other than building drainage develop from condensation of moisture rising from damp soil. The ideal method of preventing ground moisture from entering the building is to provide an impermeable vapor barrier on the warm side of insulation in floors and walls. In existing buildings this is not possible unless it is done in the course of major renovation.
The most practical solution is to provide a soil cover of water-resistant material. Fifty-five pound roll roofing has been the most widely used and successful solid cover; however, recent tests indicate that 0.006-inch polyethylene plastic sheeting is effective and lighter to handle than roofing paper. The effective life of these plastic covers has not been established when used exposed to the air or under slabs. Soil covers may be rolled out on the soil from foundation wall to wall. It is not necessary to form a complete seal over the soil; but more than 90 percent of the soil should be covered, and cracks should be limited to 1 inch. Removal of trash and debris and leveling of sharp dips and mounds in the soil will increase the life of the cover.
For inspection purposes, the basic supporting members of wood frame structures are divided into the following three groups: (1) sills and beams, (2) posts and columns, and (3) girders and joists.
Inspection and timely repair of sills and beams set on foundation walls, piers, or columns are important to the general maintenance of a structure. As in the case of uneven settlement of the foundation, severe damage can be done to the basic building by a reduction of the ability of the sill or beam to maintain upper components in their fixed position. Sill and beam defects can lead to many lesser but troublesome and expensive repairs of wall and ceiling cracks and misaligned doors and windows. Wood sills and beams should be inspected periodically for dry rot, and termite and rodent damage.Continue Reading