The demand for nonvirgin timber and lumber is restricted by the following factors:

* There are no grading standards or design rules specifically for nonvirgin wood

 materials; application of virgin material standards and rules on nonvirgin wood

 may have the effect of downgrading nonvirgin materials.

* Lumber used at a site must be graded. Without a grade, a "timber grader" must be

 present, or the materials will be rejected.

* Lack of consistent supplies and markets for nonvirgin timber and lumber.

* Owners and disposal contractors are not aware of the value of nonvirgin timber and

 lumber so they make no attempt to recover them (Falk and Lantz 1996).

Variability of the Quality of Lumber

 Service-related defects, such as drying checks, splits, bolt and nail holes, notches

from other framing members or utilities and exposure to weather and decay, can affect

the quality of recycled lumber. Depending on the building type and use, boards also may

have been exposed to chemicals and extreme temperatures. Most importantly, structural

members have often experienced an unknown load history (Green et al. 1999).

 When timber is first cut it is full of water. Before the days of drying kilns in mills,

wood was allowed to dry naturally. This process takes several years for large timbers.

As the wood dries out, the timbers shrink. The location of the cut on the tree determines

the kinds of splits or checks that occur in the wood. A split is a separation of the wood as

a result of the tearing of the wood cells (Falk et al. 2000). "A separation of the wood that

occurs across or through the growth rings is a check. A separation that extends from one

surface of a piece to the opposite or adjoining surface is a through check" (Falk et al.

2000 73). If the timber was cut from the center (the "heart" of the tree), cracks (checks)