Douglas Fir
from WWPA's Douglas Fir &
Western Larch Species Facts
published January, 1996
1996 Western Wood Products Association
Range, growth habits and production 
Douglas Fir (Pseudotsuga menziesii) is
not a true fir at all, nor a pine or spruce. It is
a distinct species named after Archibald Menzies,
a Scottish physician and naturalist who first
discovered the tree on Vancouver Island in 1791, and
David Douglas, the Scottish botanist who later
identified the tree in the Pacific Northwest in 1826.
The species is known by a number of common names
including Oregon Pine, British Columbian Pine, Red Fir
and even Douglastree; however, the U.S. Forest Service
settled on Douglas Fir some years ago. Douglas Fir is
North America's most plentiful softwood species,
accounting for one fifth of the continent's total
softwood reserves.
Western Larch (Larix occidentalis),
sometimes called Mountain Larch or Western Tamarack,
was discovered in 1806 in western Montana. However, it
remained for the botanist Thomas Nuttall to recognize
and describe the tree as a previously unclassified
species in 1834. It is one of only two conifers that
sheds its needles in the winter, with new needles
developing in spring. Western Larch is native to
eastern Oregon and Washington, Idaho, Montana, and
southern interior British Columbia. Like Douglas Fir,
it is among the strongest and hardest softwood
species.
Nearly 40 million acres of commercial
timberland* in the U.S. West are forested in Douglas
Fir and Western Larch. In addition, there are millions
more acres of Douglas Fir and Western Larch standing in
the West on the nearly 50 million acres of federal
forested land now protected from harvesting through
legislative, administrative, or judicial withdrawals,
or set aside in parks, scenic reserves, wilderness
areas, habitat reserves and research areas.
Douglas Fir timberlands are the most
productive softwood timberlands in the U.S. in terms of
volume per acre. More softwood lumber is produced in
Oregon than in any other state due in large part to the
predominance of Douglas Fir in its coastal forests.
Known as the "timber basket," where systematic
replanting has been documented since 1912, the
northwestern region is governed by some of the world's
toughest environmental laws providing protection for
habitat, watersheds, soils and biological diversity,
thus fostering a multiplicity of forest values in
perpetuity. Reforestation and management practices are
not voluntary, they are enforced by law.
For the U.S. overall, 2.4 billion trees
were planted in 1993 and a similar number are planted
every year by timberland owners, including the forest
products industry, private tree farmers and federal,
state and local agencies. Growth on Western timberlands
exceeds harvest by more than 35% overall and by more
than 50% in some areas.
In the West, timber for products is
managed primarily in natural stands, on long rotations.
It is estimated more than 557 billion board feet of
Douglas Fir and Western Larch sawtimber is growing on
commercial timberland in the west. Although production
is much greater in Douglas Fir, the two species
accounted for 45% of all Western softwood produced in
1994 -- some 7.2 billion board feet.
Douglas Fir lumber products are
identified by region. Products from trees growing west
of the Cascade Crest to the Pacific Ocean, the most
abundant region for Douglas Fir, are simply identified
as "DF" on the grade stamp. East of the Cascades,
Western Larch grows intermixed with Douglas Fir. The
two species are often kept separate in appearance grade
products but are combined in dimension products and
marketed as "DF-L". Because Douglas Fir and Western
Larch share nearly identical structural characteristics
and physical working properties, the two species are
interchangeable in dimension products.
A smaller volume of products originates
from Douglas Fir growing in Arizona, Colorado, Nevada,
New Mexico and Utah. These are identified on the grade
stamp as "DFs".
Life Cycle Inventory for WWPA
Lumber
In 1995, Western Wood Products
Association completed the Life Cycle Inventory (LCI) of
WWPA Western Lumber with Scientific Certification
Systems (SCS), an independent environmental auditing
organization in Oakland, Calif. This first life cycle
study on lumber in the U.S. was completed to the extent
possible, given current limitations in life cycle
methodology to address renewable resource
considerations.
With this LCI of Western Lumber
documentation for their products, WWPA member companies
are leading the industry in accountability by
disclosing, through an independent third party, the
environmental burdens associated with the harvesting,
manufacturing and distribution of their products.
Additional aspects of Western Lumber's life cycle will
be addressed as further guidelines are standardized
within the life cycle practitioner community.
Douglas Fir and Western Larch lumber
users may look to the registered grade mark of the
Western Wood Products Association for quality,
accountability and performance assurance on lumber
produced from the Western Woods region.
WWPA is the
leading association of lumber manufacturers in the West
and one of the largest lumber trade associations in the
world. In addition, WWPA is the only U.S. lumber
grading agency recognized by the Japanese government as
a Foreign Testing organization (FTO) authority and is
approved to grade Western Lumber under four separate
Japanese (JAS) Agricultural Standards. WWPA is also
authorized to oversee lumber graded to the Australian
Standard 2858 and British Standards 4978 and
5268.
As wood loses or gains moisture, it will
shrink or swell until it reaches equilibrium with the
constantly changing level of moisture in the air of its
immediate environment. All lumber benefits from some
degree of "seasoning," i.e. letting it adjust to the
humidity conditions of its surrounding atmosphere
before it is installed. Because of its cell structure,
wood shrinks primarily in width and thickness and very
little in length.
Douglas Fir is unique among all softwood
species in that it is naturally dimensionally stable,
having the ability to season well in position. Many
builders prefer to cut, nail and fasten Douglas Fir in
the "green" or unseasoned condition, allowing it to air
dry during construction. As a result, coastal Douglas
Fir structural lumber is often shipped unseasoned
(indicated by S-GRN on the grade stamp). Framing lumber
2 inches and less (nominal size) in thickness can be
shipped after seasoning to a moisture content of 19% or
less, which is indicated (by S-DRY or KD) on the grade
stamp. S-DRY can mean kiln dried or air seasoned, while
KD specifically means kiln dried. Regional market
conditions and building trade preferences dictate local
availability of dry or green products. In 1994, 85% of
Coastal Douglas Fir was shipped green, while 75% of
Douglas Fir and Western Larch from the inland area was
shipped dry.
For millwork, remanufacturing
applications or glued products, Douglas Fir is dried in
temperature and humidity-controlled kilns or stacked
and air dried until its moisture content (MC) reaches
the desired level for an intended purpose.
The term "dry" can be confusing in
lumber terminology. In structural grades, "DRY"
indicates a product was either kiln- or air-dried to a
19% or less moisture content level prior to surfacing.
However, in appearance products (e.g. the FINISH and
SELECT grades), "DRY" is defined in the Western Lumber
Grading Rules as being a maximum of 15% MC and, in
these grades, 85% of the items will be shipped with a
MC level of 12% or less.
(For additional information refer to WWPA's Western Lumber
Product Use Manual, Natural Wood
Siding Technical Guide, Lumber Storage
TIP sheet, and Dimensional Stability
publications.)
The WWPA grade stamp assures conformance
of the graded piece with its applicable WWPA Western
Lumber Grading Rules. WWPA is a certified lumber
rules-writing and grading agency of the American Lumber
Standard Committee, Inc. (ALSC) under the jurisdiction
of the U.S. Department of Commerce. The Association is
certified to grade and inspect lumber according to its
own Western Lumber Grading Rules, and also to the West
Coast Lumber Inspection Bureau's (WCLIB) West Coast
Lumber Standard Grading Rules and the Pacific Lumber
Inspection Bureau's Export R List Rules. These rules
provide lumber users with a dependable measure for
determining the quality and uniformity of lumber as
well as its performance capabilities.
Lumber grades, assigned on the basis of
visual inspection and/or mechanical testing, are
divided into three basic classifications which reflect
the intended end uses:
Structural lumber for
residential, commercial and industrial uses is graded
for its performance in load bearing or load-carrying
applications. Physical working characteristics are the
primary considerations and appearance is secondary.
These products are typically gradestamped with the
following information:
- Registered trademark or logo of WWPA;
- Mill name or mill number identifying the origin
of the product;
- Moisture content designation at the time of
surfacing;
- Species or species combination; and
- Grade name.
Appearance grades are
assigned to lumber intended for applications where
appearance is the most important factor. These grades
cover products ranging from the exquisitely beautiful
to the most utilitarian. They may be sold as SELECTS,
FINISH or COMMON boards, run-to-pattern for siding and
paneling products, or used for a variety of purposes.
The grades of appearance products are often certified
by written documentation rather than marked on the
lumber. Some products may be identified or gradestamped
on the back side or ends, but the highest grades are
rarely stamped to avoid marring the beauty of the
wood.
Factory and Shop grades
are assigned to lumber intended to be recut, to recover
the clear portions in the piece for manufacturing into
other wood products such as windows, doors and
cabinets, and for moulding, trim and specialty
products.
While there are special categories
within each of these broad classifications, nearly all
lumber grades fall within them. Douglas Fir products
are available in all three classifications, Western
Larch is available in structural and appearance grades,
and many Douglas Fir products are available in special
grades and sizes for international markets.
Characteristics and attributes
When architects and
engineers look for the best in structural lumber, their
first choice
repeatedly is Douglas Fir. It is
dimensionally stable and universally recognized for its
superior strength-to-weight ratio. Its high specific
gravity provides excellent nail and plate-holding
ability. The species also enjoys a documented superior
performance against strong forces resulting from
natural phenomena such as winds, storms and
earthquakes. It is truly the ideal structural and
general purpose wood for framing lumber in residential,
light commercial, multistory and industrial
construction.
The Douglas Fir/Western Larch species
combination has the highest modulus of elasticity (E or
MOE) of the North American softwood species. This is
the ratio of the amount a piece of lumber will deflect
in proportion to an applied load; it is a reflection of
the species' high degree of stiffness, an important
consideration in the design of floors and other
systems.
In strength properties, Douglas
Fir/Western Larch has the highest ratings of any
western softwood for extreme fiber stress in bending
(Fb); for tension parallel-to-grain (Ft); for
horizontal sheer (Fv); for compression
perpendicular-to-grain (Fc); and for compression
parallel-to-grain (Fc//).
These physical working properties, as
well as to the moderate durability of its heartwood and
its excellent dimensional stability, provide the
reasons many builders use Douglas Fir as the standard
against which all other framing lumber is judged. It is
also tight knotted and close-grained, adding the bonus
of beauty to its structural capabilities.
(Refer to WWPA's Product Use
Manual for additional design information and
to WWPA's Vol.1 Species Book: Dimension Lumber for
color photographs of structural grades.)
Dimension Lumber
Dimension
lumber structural grades include surfaced softwood
products of nominal thickness from 2 inches to 4 inches
in thickness by 2 inches and wider. These grades are
intended for use as general framing members, including
beams, joists, planks, rafters and studs.
The National Grading Rule for Dimension
Lumber, published in the grading rules of all
ALSC-approved agencies, classifies dimension lumber
into several basic size categories related to intended
end uses. Products are available in a variety of
lengths, beginning at 6 feet and increasing in
multiples of 2 feet.
2x2 through 4x4:
Structural Light Framing
grades in 2x2 through 4x4 of Douglas Fir and Western
Larch fit applications where the highest design values
are needed in light framing sizes for engineered
systems, trusses and multistory projects.
Light Framing grades in
2x2 through 4x4 are the building stalwarts of
residential and light commercial construction. These
grades are well suited for general framing applications
such as wall framing, plates, sills, cripples,
blocking, etc.
STUD grade is the
backbone for most interior and exterior wall framing.
characteristics affecting strength and stiffness values
are limited making STUD grade products perfectly suited
for vertical uses such as load-bearing walls. Douglas
Fir and Western Larch studs can be manufactured to the
full basic length and double-end trimmed or may be
precision-end trimmed to exact length. Some WWPA member
companies produce "wane-free" studs.
2x5 through 4x18:
Structural Joists and
Planks is a category of dimension lumber
products (2x5 through 4x18) intended to fit structural
applications for lumber 5 inches and wider, such as
floor joists, ceiling joists, roof rafters, headers,
small beams, trusses and general framing. Because of
its structural performance benefits, which rival many
fabricated products, dry Douglas Fir is also often
selected for horizontal framing in multistory wood
frame buildings; its combination of high Fb and MOE
values make it ideal for floor framing when stiffness
is a critical factor.
Large sizes
Douglas Fir is one of the few species
available in large sizes from managed timberlands. It
is preferred for heavy timber framing and large members
are available in a variety of grades manufactured for
construction uses where larger material is needed to
meet the engineering requirements of the design.
Beams & Stringers
include products that are 5 inches and thicker
(nominal) with a width more than 2 inches greater than
the thickness (i.e., 6x10, 8x12, etc.).
Posts & Timbers are
5 inches x 5 inches and larger (nominal) with a width
not more than 2 inches greater than the thickness
(i.e., 6x6, 6x8, etc.).
Douglas Fir timbers are best known for
their tough fiber, dense grain structure and strength.
they are additionally valuable for their rustic beauty
and excellent "Heavy Timber" fire ratings in the model
building codes. Timbers are shipped unseasoned and may
be specified rough cut or surfaced four sides (S4S).
Engineered Lumber
Machine Stress-Rated (MSR) lumber
Machine Stress-Rated (MSR) lumber is
distinguished from visually stress-graded dimension
lumber in that each piece is nondestructively tested
with mechanical stress-rating equipment to measure its
stiffness and other physical working properties before
it is subjected to visual inspection. Standard sizes
are 2 inches and less in thickness and 2 inches and
wider with lengths 6 feet and longer in multiples of 2
feet.
The grade stamp on MSR lumber indicates
the machine stress-rating system used meets
requirements of the grading agency's certification and
quality control procedures. The grade stamp includes
the phrase "Machine Rated" along with the E and Fb
ratings. The stamp will also include the allowable
tensile stress parallel-to-grain (Ft), the horizontal
shear (Fv) or compression perpendicular-to-grain (Fc)
design values when any of these properties are
specifically qualified. WWPA is one of the leading
agencies certifying MSR lumber.
(Refer to WWPA's MSR Lumber TIP
Sheet for additional information.)
Truss and component applications
Douglas Fir MSR lumber is often selected
for metal plate-connected trusses and other engineered
applications. however, it is also used for floor and
ceiling joists, rafters and other structural purposes
where mechanically assessed strength and connection
capabilities are primary considerations. MSR lumber is
available both seasoned and unseasoned.
Douglas Fir and Western Larch, in both
visual and MSR grades are used in roof and floor
trusses, for gable ends and wall panels, pre-cut wall
framing packages, wall sub-components, corners, doors,
beams and frames. The exceptional stiffness,
strength-to-weight ratio and plate-holding superiority
are well recognized by component manufacturers.
Structural-glued lumber products
Western manufacturers produce a variety
of Douglas Fir/Western Larch glued products from dry
lumber, including end-jointed or finger-jointed lumber,
end- and edge-glued boards, millwork and mouldings,
face-glued lumber and laminated stock. These products
make excellent use of short lengths, increasing
utilization of available timber resources.
Structural-glued dimension lumber has
gained wide acceptance in the building and construction
industry. It has been accepted for use under all model
codes and is interchangeable with solid-sawn dimension
lumber of the same size, grade and species. WWPA
provides testing and quality control for glued products
and certifies the manufacture of Douglas Fir and
Western Larch structural-glued dimension lumber under
the following classifications: Light Framing and Studs,
Structural Light Framing, Decking, Stress-Rated Boards,
and Structural Joists and Planks.
(Refer to WWPA's Structural Glued
Lumber TIP Sheet for additional
information.)
Stock for laminated beams
Structural performance is the hallmark of
Douglas Fir, but the species is also visually
beautiful. When a design calls for large beams, long
spans or unusually shaped arches as in churches,
bridges and stadiums, Douglas Fir is more often
specified than any other species. Structural-glued
laminated Douglas Fir and Western Larch beams are
engineered for use as load-carrying horizontal framing
for roofs, floors, and columns in residential,
commercial and institutional structures as well as for
towers and marine installations. These glue-lam beams
can be depended upon in industrial plants, warehouses
and factories, as well as in highly visual
architectural settings that demand uncompromising
beauty.
Laminating stock is 2 inches and thinner
and 3 inches and wider and comes in five grades and
E-RATED STRUCTURAL LAMINATIONS. This is lumber that
meets the visual grade requirements of L3 or better
structural lamination grades and has been mechanically
tested for long-span flatwise modulus of elasticity
(E). Structural laminations are specified rough or
surfaced at various widths and thicknesses up to 2
inches full. The wood is intended to be laid up
longitudinally and bonded with adhesives.
Structural decking/subflooring
Structural decking, also known as roof
decking, is 2 inches to 4 inches thick by 4 inches and
wider. This is primarily an industrial or residential
or commercial roof or floor product and should not be
confused with grades intended for exterior residential
decks. It is available in two grades: SELECTED DECKING
(for fine visual aesthetics) and COMMERCIAL DECKING
(when appearance is not of primary importance). Both
grades can be used so that the face, or better side,
will show the beauty of the wood, such as in exposed
ceilings. Decking is manufactured either at 19% (S-DRY
or KD) or 15% (MC15 or KD15) moisture content.
Standard decking patterns, in nominal 2
inches single tongue-and-groove (T&G) and 3 inches
and 4 inches double T&G, are available with "V" or
rounded edges, striated, grooved or in other patterns
to meet discriminating architectural requirements.
Douglas Fir factory floors, manufactured from dry
decking, result in a smooth, even surface so hand
trucks won't hang up and cracks and splintering won't
appear after heavy and continuous use.
Some T&G decking is
manufactured to pattern from NO.2 & BTR or NO.3,
2x6 or 2x8, S-GRN framing lumber. These products are
generally used for concealed residential subfloors in
crawl-space construction.
Characteristics and grades
For versatility and beauty, few woods in
the world match the magnificence of Douglas Fir and
Western Larch. Unlike the structural grades, appearance
lumber is milled and graded according to aesthetic
rather than structural performance criteria. Color,
grain pattern, texture, knot type and size are the
factors that influence the grade. For this reason
Douglas Fir and Western Larch are usually separated in
the appearance grades and marketed as distinct species
to allow a larger range of visual choices for
discriminating end users.
Douglas Fir's light rosy color is set off
by its remarkably straight and handsome grain pattern.
While similar, Western Larch is slightly darker in
color. Of the two species, Douglas Fir is more widely
available in the appearance grades. Both species will
"redden" over time when exposed to light. Their tough
fiber make both species difficult to work with hand
tools; however, both respond admirably to sharp power
tools and machine to an exceptionally smooth, glossy
surface. Both paint easily and can hold all types of
stains and finishes.
Moisture content levels are carefully
controlled in the highest grades to ensure these
premium products will meet the strict dimensional
stability requirements of finish carpenters, furniture
manufacturers and cabinet makers. The less "perfect"
grades are an economical choice for many utilitarian
applications.
Many designers and consumers agree the
aesthetic appeal of clear, light, straight,
vertical-grain Douglas Fir is unsurpassed among the
world's softwood species. However, the highest
appearance grades of Douglas Fir and Western Larch are
manufactured from trees older than those which yield
primarily structural framing products. And while
substantial volumes of clear and nearly clear Douglas
Fir are available from long-rotation, managed western
timberlands, the clear grades are less abundant and
considerably more expensive than knotty grades.
(Refer to WWPA's Vol.2 Species Book:
Boards and Commons for additional information and color
photographs of appearance grades in a variety of
western species.)
Interior and exterior trim, and Finish
board materials
Appearance and dimensional stability are
critical in interior and exterior trim and finish
boards, whether in the clear or knotty grades. Douglas
Fir's characteristics make it ideal for joinery: doors,
millwork, window and door casings, mantels, stairs and
baseboards. When dry, it retains its shape and size and
won't check or show a raised grain. Additionally,
Douglas Fir has an excellent performance record when
used in exposed applications for exterior trim without
ground contact.
(Refer to the "TREATED PRODUCTS"
section for in-ground and ground-contact
information.)
Clear and knotty grades
The highest grade categories, "Finish"
and "Selects," include the grades for clear and nearly
clear lumber in either vertical or flat grain. (If
grain pattern is not specified, these grades will be
shipped as a mixed grain combination of vertical and
flat grain.) Finish and Select grades of Douglas Fir
are recommended for interior trim and cabinet work with
either natural, stain or enamel finishes where the
finest appearance is important.
Douglas Fir "Commons" (WWPA Rules) or
"Alternate Boards" (WCLIB Rules) are typically used for
shelving, sheathing or run-to-pattern for siding and
paneling. These products are nominal 1 inches
thickness, surfaced to 3/4 inches and are generally
gradestamped on the back or ends.
The highest grades are used where fine
appearance in a knotty material is required, such as
for soffits, fascia, cornices, shelving or
run-to-pattern for siding and paneling. Depending on
the criteria for the application, other grades in
knotty products are used primarily in housing and light
construction where wood is exposed for its beauty and
character (e.g. shelving, paneling, siding, fences,
boxes) or for its utility and serviceability in
crating, sub-floors, roof and wall sheathing and
concrete forms. The lowest grades are useful in
applications where economy is the basic
requirement.
Wood paneling, cabinets and
furniture
Designers appreciate the rich visual
quality of Douglas Fir texture and grain as well as its
beautiful response to fine craftsmanship and finishing.
A favorite wood for custom cabinets, furniture and
millwork, it works easily and resists wear. When sawn
to expose vertical grain, Douglas Fir is particularly
handsome.
Douglas Fir paneling can transform any
room into a dramatic, elegant space. The wood's fine
appearance is clearly visible in a variety of
applications such as edge-grain veneers for formal wall
paneling or solid plank paneling for an informal look.
When acclimated prior to installation, Douglas Fir
retains its shape and size without shrinking, swelling,
cupping, warping, bowing, or twisting. The uniform
grain and tough fiber holds stain well and keeps
fasteners firmly in place.
Douglas Fir (and Western Larch to a
lesser extent) paneling is run in a variety of
patterns. In many cases, the grade of the patterned
material reflects the grade of the starting material,
adhering to similar requirements for allowable
characteristics. Grades for paneling include the finish
grades for highest appearance and the Commons or
Alternate Board grades for knotty products.
(Refer to WWPA's Standard
Patterns publication for dimensioned, scaled
profiles of standardized WWPA siding and paneling
patterns. Refer to WWPA's Guide to Real Wood Interiors
for information on selecting, specifying, installing,
finishing and maintaining solid wood
paneling.)
Flooring
Wood floors in gyms, factories and homes
take an incredible beating. Douglas Fir's strength,
beauty and old-fashioned toughness are all prime
reasons for choosing this long-lasting wood. Douglas
Fir provides a tough surface that will hold a finish,
maintain its appearance under extreme wear, and remain
level without cracking, scuffing or splintering.
Douglas Fir flooring is available
in 1 inches x 4 inches (nominal) sizes in standard
lengths 4 and longer. Flooring is machined
tongue-and-groove and may be finished in any grade;
however, the grade specifically developed for flooring
is C & BTR FLOORING, which can be sawn vertical
grain for a more refined look.
Characteristics and grades
Douglas Fir has an enviable performance
record. The species has earned respect from industrial
users worldwide because when it comes to high
performance demands and extreme stress conditions,
Douglas Fir meets the test. With its tough, strong
fiber, high strength in relation to its weight, and its
dense grain structure, Douglas Fir is a natural choice
for industrial and remanufacturing uses.
Being highly resistant to mechanical
abrasion and chemical reaction, Douglas Fir is often
used in fabricating vats, tanks, containers, flumes,
conduits and similar industrial components that call
for an inert material with a long life under rigorous
service conditions. Truss fabrication and formwork,
mining and tunneling, trestles, bridges, railroad ties,
stadiums, warehouses, storage facilities and factories
-- all depend on Douglas Fir.
Industrial products include both
structural and non-structural grades that are intended
for specific applications. Structural grades are used
for mining timbers, scaffold plank, foundation lumber
and stress-rated boards. Specialized non-structural
grades include pickets, lath, battens, stepping and
even gutters (used primarily for historic preservation
projects). Factory and Shop lumber, one of the three
primary grading classifications of Western Lumber
products, is non-structural, industrial lumber intended
for remanufacturing into an enormous array of
products.
Factory and Shop lumber
Millwork standards require that the wood
be easy to machine, be of a consistent grade, have few
visible knots, be dimensionally stable and have a
smooth surface texture. In addition, the grain must be
handsome in appearance, the wood easy to glue, hold
fasteners well and readily accept finishes. Three
western softwood species are consistently specified for
millwork: ponderosa Pine, Douglas Fir and Hem-Fir (a
species combination of Western Hemlock and the true
firs). When hardness is desired, in addition to fine
appearance, Douglas Fir rivals many hardwoods.
Factory lumber is produced primarily for
doors, windows, furniture, frames, moulding and boxes.
The grades are especially well suited for ripping and
cross cutting to obtain clear pieces for
remanufacturing. Factory grade criteria includes
specifications, within the grades, for the percentage
of the lumber that is available for cuttings in
predetermined sizes and qualities, based on typical
U.S. joinery and millwork specifications. Moulding
stock, which comes in several thicknesses and widths,
is suitable for ripping into strips 1 inch and wider by
10 feet and longer.
Shop lumber, nominal 4/4 thickness to
16/4, is used in remanufacturing for sashes and doors,
jambs and door component parts, boxes and specialty
goods.
Factory and Shop lumber is usually
shipped in large quantities, mill-direct to
remanufacturers. Many WWPA member companies can
accommodate special remanufacturing requirements
through buyer/seller agreements.
(Refer to WWPA's Vol.3 Species Book:
Factory Lumber for additional information and color
photographs of the Factory and Shop grades.)
Stress-rated boards
Stress-Rated Boards are available in
Douglas Fir to provide a range of products suitable for
special applications where applied design values are a
requirement. Uses include light trusses, belt rails,
horizontal bracing, rafters, and box beams for factory
built homes. When Stress-Rated Boards are gradestamped,
the grade name or number for the dimension grade will
be shown on the grade stamp along with "SRB" to
designate that a board product may be used
structurally.
Highways, bridges and railroads
Douglas Fir bridges -- either in the
solid sawn designs of past years or in today's glued,
stress-laminated forms -- span roads and rivers, lead
hikers into the wilderness or over gorges and offer
access for everything from golf carts to semi-trailers
and heavy machinery. Douglas Fir is a top choice when
the material must resist slivering and indentation, be
strong, durable, functional and yet, at home in its
natural surroundings.
While wooden bridges have been around for
centuries, today's engineered bridges of treated wood
offer communities some new advantages. they are strong,
durable, cost-effective, time efficient to install and
reduce the impact of construction on surrounding
streamside ecology. Today's technology for
stress-laminated wood bridges is gaining wide
acceptance throughout the U.S. and in other
countries.
Douglas Fir is also the species of choice
for sound barrier walls along freeways or for highway
guard rails which demand a wood that is treatable,
paintable and strong with excellent fastening
capability.
Given its resilience under
tremendous loads and vibration, and the ability to take
and hold heavy railroad spikes tightly, it's clear why
Douglas Fir still dominates the railway tracks. From
rail car linings and track supports to ties and
cross-planking, this western species, treated and
untreated, provides long-lasting solutions to very
tough jobs.
Douglas Fir preservative pressure-treated
wood pilings provide long-life performance with
resistance to the corrosive salt water conditions of
wind, waves, storms and tides. When dramatic design
solutions are called for on hillsides or in hurricane
country, pressure-treated Douglas Fir pole construction
is often the best and most economical solution. Design
loads as high as 70 tons have been specified and
ultimate loads as high as 235 tons have been carried by
Douglas Fir lumber. Treated DF products are also
consistently found in foundation stud and plywood
walls, vehicular bridges, walkways, parks shelters and
foot bridges.
In pressure treating, preservatives are
forced into the wood cells and become permanently fixed
(nonleaching). Because of its cell structure, Douglas
Fir requires incising (small slits cut into the wood's
surface before treatment) to improve chemical
penetration. Chemical retention is stated in terms of
the weight of the chemical retained per cubic foot
(pcf) of wood after treatment; the larger the number,
the more chemical retained.
The American Wood Preservers Association
(AWPA) provides treating standards and retention levels
for a number of chemicals. All pressure-treated wood
should bear the quality control mark of an agency
approved by the American Lumber Standard Committee.
In general, relevant AWPA standards and
retention levels for waterborne preservatives are:
- 0.25 pcf to AWPA Standard C-2 is required when
the product is used above ground;
- 0.40 pcf to AWPA Standard C-2 is required if the
lumber is in contact with soil or fresh water;
- 0.60 pcf to AWPA Standard C-15 is required of the
lumber is used as a permanent wood foundation.
For more information refer to WWPA's
Treated Lumber TIP Sheet or the Western Wood
Preservers Institute's brochure Guide to the
Characteristics, Uses and Specifications of Pressure
Treated Wood.
Quality control
In the U.S., Douglas Fir and Western
Larch are often milled and shipped as a species
combination (DF-L) in dimension products for structural
applications. However, large volumes of
structural-grade Douglas Fir, as a distinct species,
are also produced and shipped as both unseasoned and
dry products. In appearance products, the two species
are usually marketed separately. Western Larch, as a
species, is less available than Douglas Fir in all
product categories.
The WWPA grademark
identifies Western Lumber products backed with
assurances for quality, performance and technical
support. WWPA maintains a team of lumber inspectors
throughout the Western region to monitor the grading
and quality control of Western Lumber products from
WWPA Member mills, ensuring products consistently meet
grade specifications. Additionally, WWPA has technical
experts on staff with training and work experience in
design, engineering, lumber specifications, code
conformance, construction, manufacturing, wood
technology and forestry. From the Association's
headquarters, these experts offer technical assistance
in all aspects of Western Lumber end use for WWPA
Member company products.
To order a full-color version of
this publication, complete with photos and examples of
grades, or any other WWPA title referred in this text,
go to the WWPA Publications List.
For a list of WWPA Member mills that produce Douglas
Fir lumber products, go to
the WWPA Online Buyers' Guide section.
Western Wood Products Association
522 SW Fifth Ave., Suite 500, Portland, Oregon
97204-2122
Phone: 503-224-3930, Fax: 503-224-3934, E-mail:
info@wwpa.org
Internet location:
http://www.wwpa.org Internet Presence: ÔøΩ
1997, Western Wood Products Association
