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LUMBER GRADE AND QUALITY MARKS
To be certain the treated Southern Pine lumber for framing
is of a quality to meet its intended use, insist that it be grade-marked
by an agency accredited by the American Lumber Standard
Committee (ALSC). An ALSC-accredited grade mark on
Southern Pine
lumber indicates
that the lumber
has been properly
seasoned prior
to treatment and
that it meets the
structural and
appearance
requirements
established for
the grade.
In addition,
all treated Southern
Pine should
conform to the
approved standards of the American Wood Protection Association
(AWPA). Each piece should be treated in accordance with
AWPA standards and identified with a quality mark (either ink
stamp or plastic end tag) by an ALSC-accredited inspection
agency.
For the lumber grade mark to be valid after treatment, the
lumber must adhere to the grade requirements and the moisture
content of the grade represented by the grade mark.
Fasteners and Connectors
The International Residential Code (R319.3) and the International
Building Code (2304.9.5) have similar requirements for fasteners used
with treated wood. The IRC states, "Fasteners for pressure-preservative
and fire-retardant-treated wood shall be of hot-dipped zinc-coated
galvanized steel, stainless steel, silicon bronze or copper. The coating
weights for zinc-coated fasteners shall be in accordance with ASTM A153.
Exceptions: 1. One-half inch (12.7mm) diameter or greater steel bolts.
2. Fasteners other than nails and timber rivets shall be permitted to be
of mechanically deposited zinc-coated steel with coating weights in
accordance with ASTM B695, Class 55, minimum."
The codes do not discriminate between types of preservatives and do not
take into account exposure conditions, nor do they contain provisions
for other hardware such as connectors or flashing. Therefore,
clarification is helpful to assist the specifier.
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PRESSURE-TREATED PLYWOOD
Just like lumber, softwood plywood for structural sheathing
applications can be pressure treated with preservatives. The same retention levels
for chemical treatment used in termite-resistant lumber framing
should be used for treated plywood sheathing. Treated plywood
used in residential and commercial buildings should be
kiln dried after treatment (KDAT) to 18% moisture content or
less to meet building code requirements. Similar to KDAT
lumber, KDAT plywood maintains all of its strength, shear and
stiffness, thermal properties, workability, light weight, and
economy.
CONSTRUCTION CONSIDERATIONS
Pressure-treated Southern Pine lumber is recognized by all
the major model building codes. Building codes further state
that, when used in enclosed locations, the wood must be at 19%
MC or less at the time of permanent enclosure.
Design values published by the Southern Pine Inspection
Bureau in its Standard Grading Rules for Southern Pine Lumber,
2002 Edition, apply to both treated and untreated Southern
Pine. Design values for dimension lumber are based on normal-use conditions in covered structures where moisture content
will not exceed 19%, or in other applications where the
moisture content in use does not exceed 19% for an extended
period of time.
THE "WHOLE HOUSE" TREATMENT CONCEPT
Using preservatively treated
Southern Pine for the framework
of the entire structure
offers the property owner one
of the best-known, most
cost-effective materials for full
protection against Formosan
termites. This concept is
known as “whole house” treatment.
Used in conjunction with traditional termite controls
(ground-line treatments, termite barriers, etc.), it offers the
most practical defense against termite damage.
Builders and homeowners in states where Formosan termites
are most active are beginning to use the "whole house"
treatment concept to protect their properties. Successful examples
of new construction employing this concept are found
throughout the Greater New Orleans area, where battling the
Formosan subterranean termite has become a way of life.
COMPARATIVE COSTS: TREATED vs. UNTREATED
The added cost of using treated wood framing, even for use in the entire wood framing structure of a home, is very modest when considering the entire investment homeowners have in their property. This added cost can be considered a minimum insurance-type cost used to protect what is often a person’s single largest investment: their home!
The alternative cost of repair, eradication, or replacement
of structural members due to attack by Formosan termites in
unprotected homes is almost always exponentially higher than
the small added cost of using treated wood framing at the time
of original construction.
ADDITIONAL INFORMATION
Mill direct, volume buyers may find
primary producers of pressure-treated Southern Pine products using the product locator. The Southern Pine Council offers a wide variety of
other helpful publications. A single copy is free upon
request. Materials available and the cost per copy for
quantities include:
- Pressure-Treated Southern Pine (#300, $2.00) 20 pages.
Treating process, preservative types and retention levels, product standards.
- Southern Pine Use Guide (#200, $2.00) 24 pages.
Grade descriptions, design values, standard sizes, specification guidelines.
- Raised Floor Systems: Design & Construction Guide (#411, $3.00) 48 pages
Advantages, cost comparisons, design and construction details.
- A Guide to Southern Pine Porch Flooring (#313, $1.00) 4 pages.
Proper specification, installation, and finishing of porch flooring.
1. Research conducted as part of the Economic Impact Committee of the Louisiana
Department of Agriculture and Forestry (a working group organized within the Louisiana
Formosan Termite Initiative Project), September 2000.
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