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Most manufacturers
provide only air-dried logs. These logs are seasoned by simply storing
them for an extended period of time. The important point here is to make
sure the customer asks the manufacturer of the air-dried materials to guarantee
the moisture content levels. It's technically possible to air-dry logs to
15% moisture content. From a practical standpoint, however, it is not
usually done. Under normal conditions, logs would need years of
air-drying to match kiln-dried standards, however, still lacking the additional
kiln-dried benefit of sanitized logs.
Briefly, some of the
other benefits associated with kiln-drying are:
a) Kiln-dried logs are preshrunk before milling to a final profile. Uniform and
stable - no severe shrinking or warping. Tight joints.
b) Careful drying in a controlled environment minimized checking (cracking),
which occurs in the kilns, before milling and final construction.
c) Warping and twisting occur during kiln-drying, before construction.
Defective logs can be graded out by trained inspectors. Logs built into
the home should then be stamped with the NAHB certification for Stress Grades
and Moisture Content.
d) Logs are sanitized when heated to 170 degrees Fahrenheit in the kiln.
Such heat kills mold, fungi which causes wood decay, as well as any insects,
their eggs or larvae.
e) Pitch in the wood is crystallized during kiln-drying, preventing the sticky
substance from seeping to the surface.
f) Interior and exterior finishes can be applied immediately following
construction for more convenient and immediate protection. Applications
absorb deeper and last longer.
g) More than 10,000 pounds of water are removed from the typical home,
significantly reducing the weight of the logs. Even the longest logs are
easily handled by two people.
In recent years more
prospective log home buyers are asking questions, considering, and choosing
kiln-dried logs when building their home. With this apparent, many log
home manufacturers are now offering kiln-drying as an option. It is very
important for those considering kiln-dried logs to understand how the term can
often be misinterpreted.
Kiln-drying is not
achieved by running cants through a pre-dryer, which are used to reduce the
surface moisture of wood with large fans. This process is intended as a
superficial treatment only as warm air is circulated by fans. The
temperature in pre-dryers does not approach the heat generated by a dry-kiln,
and the humidity is controlled only to the extent of venting some of the
moisture-laden air. Pre-dryers DO NOT sanitize the logs.
If a log home buyer is
shopping for a kiln-dried log home, they should ask the manufacturer the
following questions:
1. who, where, and how are the logs dried?
2. What temperature levels are achieved in the kiln?
3. What moisture content are the logs dried, and is the moisture content
guaranteed in writing?
4. What process is used in determining the moisture content (moisture probe
which measures the level on the exterior portion of the log only, or the
"oven-dry-ratio" method)?
The benefits of
kiln-drying are not limited to the United States. According to the
International Trade Council (ITC) of the American Forest Products Association
(AFPA), effective June 1, 1993, European Community regulations require that all
coniferous lumber be heat-treated (sanitized) and be accompanied by a
phytosanitary certificate. Shipments not meeting these requirements may
be rejected.
The regulations go a
step further, forbidding the import of green lumber, even if accompanied by a
phytosanitary certificate because European Community regulations require
heat-treatment of all coniferous lumber. Imports of large-dimension lumber that
has not been heat treated are also forbidden. | 
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