Installation Guide

2
Premium grades have fewer
characteristics such as knots, pitch
streaks and so forth. The highest
designations are reserved for clear
wood free of characteristics. These
grades are generally more expen-
sive and usually sold kiln dried.
While some B&Btr is available,
Select grades usually include C and
D Select. (Equivalent grade desig-
nations in Idaho White Pine are
Supreme, Choice and Quality.)
Western Red Cedar may be graded
as Selects or according to Cedar
Rules where comparable grades
are Clear Heart, A and B grades.
Finish grades include Superior and
Prime, and can be used for most
Western species but are seldom
used for the cedars and pines.
Additional grades for bevel patterns
are shown in Table 1. Specify exact
grade desired, by grade rule book
and paragraph number.
Knotty grades such as
Common, Alternate Board, Select
Knotty and Quality Knotty are more
abundant as they include material
with knots and other characteris-
tics.
Knot size and quality are defined
in the grading rules. Sound, tight
knots will not adversely affect the
performance of the siding.
However, encased or unsound
knots can become loose and may
eventually fall out.
WWPA knotty grades include 1, 2
and 3 Common. (Equivalent grades
in Idaho White Pine are Colonial,
Sterling and Standard.) These
grades are generally referenced as
2&Btr Common and 3&Btr
Common for most Western
species. (Refer to notes under
Table 1 for additional information.)
The WCLIB knotty grades for
Alternate Boards are Select
Merchantable, Construction and
Standard. Similar knotty grades for
cedar siding are Select Knotty and
Quality Knotty.
When selecting knotty siding in
any species, specify the exact
grade or paragraph number of the
grade rule book from an ALSC-
Natural Wood Siding
Solid wood has long been used
as a siding material. Its natural
beauty is timeless and the color
and textures available are
unmatched by other building prod-
ucts. Such properties make wood
siding adaptable to a wide variety
of regional preferences, architectur-
al styles and climates.
When correctly installed and
maintained, natural wood siding will
last for decades and sometimes
centuries. It is a prestige product
that adds value to a home or com-
mercial building, reflecting both
quality materials and professional
workmanship.
Grades
Building codes usually consider
wood siding a non-structural mater-
ial and place few restrictions on its
use. In addition, model codes do
not require that it be grade-
stamped.
However, all Western species
used for siding are listed under at
least one industry-recognized grade
rule published by an American
Lumber Standard Committee, Inc.
accredited rules-writing agency,
such as Western Wood Products
Association (WWPA).
Western species of the United
States include Douglas Fir and
Larch, Hemlock and the True Firs,
Ponderosa Pine, Lodgepole Pine,
Idaho White Pine, Sugar Pine,
Engelmann Spruce, Sitka Spruce,
White Spruce and the Western
Cedars.
Cedar’s weather resistance and
dimensional stability make it
particularly well suited to siding
applications, with the added benefit
that cedar’s heartwood is naturally
durable against decay. Clear Heart
and Clear VG Heart grading rules
include the heart designation. If
heartwood is desired in other
grades, and sapwood to be limited,
then it must be so specified
through buyer/seller agreement.
Siding products are generally cat-
egorized as either premium or
knotty grades.
Contents
Grades . . . . . . . . . . . . . . . . . . . . . 2
Pattern Selection . . . . . . . . . . . . . 3
Moisture Content . . . . . . . . . . . . . 3
Checklist for a
Siding Specification . . . . . . . . . . 4
Priming and Prefinishing . . . . . . . . 4
Installation . . . . . . . . . . . . . . . . . . . 5
Pattern & Installation (Nailing)
Diagrams . . . . . . . . . . . . . . . . . . 6
Nails & Nailing . . . . . . . . . . . . . . . 8
Finishing . . . . . . . . . . . . . . . . . . . . 9
Coverage Calculations . . . . . . . . 10
Checklist for High
Performance Siding . . . . . . . . . 11
Additional Information . . . . . . . . . 11
Western Lumber Grade
Reference Chart . . . . . .
back cover
Natural Wood Siding:
Selection, Installation & Finishing
Western Wood Products Association
522 SW Fifth Avenue, Suite 500
Portland, OR 97204-2122
503-224-3930 fax: [phone]
e-mail: [e-mail]
website: www.wwpa.org
©2007 WWPA