floor construction and as substitutes for studs and rafters in
wall and roof construction. Various types of SCL are also
used in a number of nonstructural applications, such as the
manufacture of windows and doors.
Standards and Specifications
The ASTM D 5456 (ASTM 2008b) standard provides meth-
ods to develop design properties for SCL products as well as
requirements for quality assurance during production. Each
manufacturer of SCL products is responsible for developing
the required information on properties and ensuring that the
minimum levels of quality are maintained during produc-
tion. An independent inspection agency is required to moni-
tor the quality assurance program.
Unlike lumber, no standard grades or design stresses have
been established for SCL. Each manufacturer may have
unique design properties and procedures. Thus, the designer
should consult information provided by the manufacturer.
Wood–Nonwood Composite
Materials
Wood may be combined with inorganic materials and
with plastics to produce composite products with unique
properties. Wood–nonwood composites typically contain
wood elements suspended in a matrix material (for example
in fiber-reinforced gypsum board, or in thermoplastic mate-
rial), in which the proportion of wood elements may account
for less than 60% of product mass.
The primary impetus for developing such products has come
from one or more of the following research and develop-
ment goals:
• Develop “green” or “environmentally benign” products
with enhanced sustainability.
• Reduce material costs by combining a lower cost mate-
rial (acting as a filler or extender) with an expensive
material.
• Develop products that can utilize recycled materials and
be recyclable in themselves.
• Produce composite products that exhibit specific prop-
erties that are superior to those of the component mate-
rials alone (for example, increased strength-to-weight
ratio, improved abrasion resistance, enhance resistance
to fire, decay, and insects).
Composites made from wood and other non-wood materi-
als create enormous opportunities to match product perfor-
mance to end-use requirements. The following discussion
includes the most common type of wood–nonwood compos-
ites: inorganic-bonded and wood–thermoplastic composites.Inorganic-Bonded Composite Materials
Inorganic-bonded wood composites have a long and varied
history that started with commercial production in Austria
in 1914. They are now used in many countries in the world,
mostly in panel form. Applications include panel products,
siding, roofing tiles, and precast building members.Figure 11–15. Generalized process for manufacturing PSL. (Courtesy of iLevel by Weyerhaeuser,
Federal Way, Washington. Used by permission.)General Technical Report FPL–GTR– 190