Installation, Care, and 

Maintenance of Wood 

Shake and Shingle Siding

Jack Dwyer

Tony Bonura 

Arnie Nebelsick

Sam Williams

Christopher G. Hunt

United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

General

Technical

Report

FPL–GTR–202
October 2011

Dwyer, Jack; Bonura, Tony; Nebelsick, Arnie; Williams, Sam; Hunt, 

Christopher G. 2011. Installation, care, and maintenance of wood shake 

and shingle siding. General Technical Report FPL-GTR-202. Madison, WI: 

U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 13 p.

A limited number of free copies of this publication are available to the 

public from the Forest Products Laboratory, One Gifford Pinchot Drive, 

Madison, WI 53726–2398. This publication is also available online at 

www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of libraries 

in the United States and elsewhere.

The Forest Products Laboratory is maintained in cooperation with the 

University of Wisconsin. 

The use of trade or firm names in this publication is for reader information 

and does not imply endorsement by the United States Department of 

Agriculture (USDA) of any product or service.

The USDA prohibits discrimination in all its programs and activities on the 

basis of race, color, national origin, age, disability, and where applicable, 

sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part 

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Avenue, S.W., Washington, D.C. 20250–9410, or call (800) 795–3272 

(voice) or (202) 720–6382 (TDD). USDA is an equal opportunity provider 

and employer.

Abstract 

This article gives general guidelines for selection, installation, finishing, and maintenance of wood shakes and 

shingles. The authors gathered information from a variety of 

sources: research publications on wood finishing, technical 

data sheets from paint manufacturers, installation instructions for shake and shingle siding, and interviews with 

experts having experience constructing and inspecting shake 

and shingle siding. If research reports could not be found, 

the recommendations are based on opinions of experts and 

practices that have been shown to give good service life for 

shakes and shingles. More detailed information is available 

from shake and shingle suppliers, paint manufacturers, and 

the Cedar Shake and Shingle Bureau (CSSB).

Keywords: Shakes, shingles, ultraviolet radiation, UV 

degradation, water-repellent preservatives, semitransparent 

stains, solid-color stains, paints

Contact author is Tony Bonura (District Manager/Northeast, 

Cedar Shake and Shingle Bureau, 1019 Fort Salonga Rd., 

Suite 10-#203, Northport, NY 11768-2209, Phone/Fax 

631-643-7839, tony@cedarbureau.com, 

www.cedarbureau.org).

Authors are members of the Joint Coatings Forest Product 

Committee. The American Coatings Association and the 

Forest Products Laboratory co-sponsor the committee and it 

is comprised of representatives from the wood and coatings 

industries. The committee functions through task groups 

organized to write articles on wood/paint interaction. Jack 

Dwyer chaired the Shake and Shingle task group until he retired; Tony Bonura chaired the task group after Jack retired.

Contents

Introduction......................................................................... 1

Selection.............................................................................. 1

 Shakes............................................................................. 1

 Shingles........................................................................... 2

 Specialty Sidewall Products............................................ 3

Installation........................................................................... 5

 Rain-Screen Method ....................................................... 5

 Direct Application........................................................... 6

 Application Over Existing Siding ................................... 6

Fasteners ............................................................................. 7

Finishes............................................................................... 8

 Finish Selection............................................................... 8

 Finish Application........................................................... 9

Maintenance...................................................................... 10

 Removal of Algae, Mold, and Iron Stains..................... 10

 Finished Surfaces.......................................................... 11

 Refinishing.................................................................... 11

Safety Precautions............................................................. 12

Other Sources of Information ........................................... 12
Installation, Care, and Maintenance of Wood 

Shake and Shingle Siding

Jack Dwyer, State of Vermont, retired

Tony Bonura, Cedar Shake and Shingle Bureau, Northport, New York

Arnie Nebelsick, Edmund Allen Lumber Company, Momence, Illinois

Sam Williams, Forest Products Laboratory, Madison, Wisconsin, retired

Christopher G. Hunt, Forest Products Laboratory, Madison, Wisconsin 

The Cedar Shake and Shingle Bureau (CSSB) is a 

nonprofit organization that oversees the inspection of 

western redcedar (Thuja plicata), Alaska yellow-cedar 

(Chamaecyparis nootkatensis), and redwood (Sequoia 

sempervirens) shakes and shingles. The CSSB publishes quality standards (grade rules) and ensures that 

the member mills producing shakes and shingles meet 

these standards through periodical third-party inspection. Shakes and shingles having their “Certigrade®,” 

“Certi-Split®,” or “Certi-Sawn®” designations have 

been inspected to meet grade standards. A grade stamp/

label (with color code for the grade) is placed on each 

bundle or carton of shakes or shingles and clearly 

shows the grade. The label contains other information 

such as wood species, certifying agency, building code 

standards, and manufacturer (Fig. 1). This “Certi” label 

assures the consumer that the shake and shingle manufacturer is adhering to grading rules as prescribed by 

building codes.

Introduction

Wood shakes and shingles have been used for centuries as a 

siding material. Western redcedar, Alaska yellow-cedar (also 

called yellow cedar), and redwood are the wood species 

most commonly used to manufacture shakes and shingles. 

Shakes and shingles from these species are included in the 

building codes for the United States and Canada, and to 

meet these building code requirements, shakes and shingles 

must meet specific wood quality standards (Table 1). 

Eastern white-cedar (also know as northern white-cedar, 

Thuja occidentalis) is also currently used for shingles, 

and grade rules are established for this species (Table 2). 

Shingles from this species are not covered under CSSB standards and their quality is not certified through third-party 

inspection; therefore, their use on roofs is not authorized 

under United States and Canadian building codes. However, 

they are approved for use on sidewalls. Check with local 

code officials for details. Other species have historically 

been used for shakes and shingles: white oak (Quercus alba) 

and southern pine (also called southern yellow pine, Pinus

spp.). The quality of white oak and southern pine shakes and 

shingles is not assured through CSSB inspection; therefore, 

check with code officials in your area for acceptance of 

these products.

Wood shakes or shingles, if properly installed, finished, and 

maintained, will age gracefully providing a long service life 

(Fig. 2). 

Selection

The first requirement for long service life is selection of the 

shake or shingle. Western redcedar, Alaska yellow-cedar, 

and redwood are available in a range of grades (Table 1). 

They are listed in decreasing quality along with a brief 

description of the grade. This is where “money talks!” The 

higher the grade (and price), the longer the siding can be 

expected to last. Vertical-grain (or edge-grain) shakes and 

shingles will probably perform better than flat-grain grades; 

vertical-grain wood is more dimensionally stable and 

therefore less likely to warp and split. 

Some areas of the United States and Canada have code 

requirements for fire-treated shakes and shingles for roofs

and siding. Chromated copper arsenate (CCA) preservative treated shakes and shingles are also available. This is 

probably not required for shakes and shingles used in siding 

applications, but it is prudent to check. Even if not required, 

CCA pressure-impregnation of shakes and shingles can dramatically extend their service life, especially in areas where 

warm temperatures and humid conditions are present for 

substantial parts of the year. Non-pressure treatments such 

as with copper 8-quinolate and copper napthenate are also 

available, but these are not as leach resistant as pressureapplied preservatives.

Shakes

Shakes come in a variety of sizes, shapes, and surfaces and 

are graded on the split side. Shakes are most commonly 

available in 18-in. (457-mm)1 and 24-in. (610-mm) lengths, 

but longer lengths can be special ordered. Shakes can be 

split on the face and have sawn backs (handsplit), split on 

both sides (straight split and tapersplit), or sawn on both 

sides (tapersawn). Handsplit shakes are graded on the split 

side. Tapersawn shakes are commonly available having 

butt-end thickness of 5/8, 3/4, and 7/8 in. (16, 19, and 

22 mm), may be special ordered up to 2 in. (51 mm) buttend thickness, and are graded on the best face. All shakes 

1The variability in manufacturing results in large variance in 

measured values of shakes and shingles, which are not necessarily 

reflected in the precision of the reported conversions to SI units.
General Technical Report FPL–GTR–202

2

are graded to one face according to the grain angle, flaws, 

and heartwood/sapwood content (available in two grades, 

Premium and No. 1). A brief description of each grade is 

contained in Table 1 and Figure 3.

Additional information on grades and grade rules is 

contained in “CSSB-97 Grading and Packing Rules 

for Western redcedar, Alaska yellow-cedar (also called 

yellow cedar) and Redwood Shakes and Shingles. 

These grade and packing rules are available on the 

Cedar Shake & Shingle Bureau’s website: 

www.cedarbureau.org.

Shingles

Shingles are sawn on both faces and have a butt-end 

thickness of about 3/8 to 1/2 in. (9.52 to 13 mm). Western 

redcedar, Alaska yellow-cedar, and redwood shingles are 

graded according to the grain angle, flaws, and the amount 

of heartwood/sapwood and are available in four grades 

(Fig. 4).

No. 1 grade shingles must be 100% clear, 100% heartwood, 

and 100% vertical grain. Shingles that contain only heartwood are more resistant to decay than are shingles that 

contain sapwood. Lower grades may contain sapwood, flat 

grain, and knots. Vertical-grained shingles are less likely 

to warp and split than are flat-grained shingles. Narrow 

shingles are less likely than wide shingles, and thicker less 

likely than thinner shingles to warp and split. Thickness of 

shingles is described as the number of shingles per the total 

of butt-end thickness of a specific length of shingle. 

For example, a 24-in. by 4/2-in. (610-mm by 4/51-mm) 

“Royal” shingle measures approximately 1/2 in. at the butt. 

That is, the total butt-end thickness of 4 shingles must be 

at least 2 in. (51 mm). An 18-in. by 5/21⁄4-in. (457-mm by 

Figure 1. Information on a Certi-LabelTM: 1) “Certi” brand name; 

2) Product grade; 3) Product type; 4) Independent third party quality control agency; 5) Compliance with total quality processes; 

6) Manufacturer; 7) Industry product description; 8) Product 

dimensions; 9) Cedar Shake and Shingle Bureau label number; 

10) Building code compliance numbers; 11) Product performance 

tests passed; 12) Label identification number; 13) UPC code; 

14) Coverage showing the number of bundles/100 square-feet 

and recommended exposure; 15) Application instruction on reverse 

side. Used with permission from Cedar Shake and Shingle Bureau 

Exterior and Interior Wall Manual. 
Installation, Care, and Maintenance of Wood Shake and Shingle Siding

3

5/57-mm) “Perfection” measures approximately 7/16 in. at 

the butt. That is, the total butt-end thickness of 5 shingles 

must be at least 21⁄4 in. Lengths may be 16, 18, or 24 in. 

(406, 457, or 610 mm). A 16-in. (406-mm) shingle is referred to as a “5X” because they are installed with a 5-in. 

exposure. Shingles are available in specified widths or 

random widths. Figure 5 shows a typical modern structure 

having random-width shingle siding. 

Specialty Sidewall Products

Rebutted and Rejointed Shingles

Rebutted and rejoined shingles (commonly known as R&R 

shingles) are kiln-dried and may be specified as having a 

“sanded” or “un-sanded” face (Fig. 6). The length of the 

sanded face is greater than the maximum exposure. These 

shingles are identical to No. 1 and No. 2 grades and must be 

specified as No. 1 or No. 2, but are machined to have parallel edges and smooth butt-ends. They are used for sidewall 

application. This product is available in 16-, 18-, and 

24-in. (406-, 457-, and 610-mm) lengths.

Machine-Grooved Shingles

Machine-grooved shingles are identical to rebutted and 

rejointed shingles but have grooves machined on the face 

of the shingle (Fig. 6). Machine grooved products are for 

sidewall applications only. This product is available in 16-, 

18-, and 24-in. (406-, 457-, and 610-mm) lengths.

Table 1. Grade and description of shakes and shingles from western redcedar, Alaska yellow-cedar, and 

redwood

Gradea

 Description 

Shakesb

Premium Handsplit, tapersawn, tapersplit, or straight-split shakes from 100% clear vertical-grained 

heartwood. Tapersplit shakes have a natural taper that is similar to the taper of a shingle. Straightsplit shakes are of the same thickness throughout the length of the shake. 

No. 1 Handsplit and tapersawn shakes of clear heartwood with no more than 20% flat-grained pieces in 

each bundle. 

Shinglesc

No. 1 The top grade of shingles. This grade of shingle can be used for sidewalls and roofs. This grade of 

shingle must be 100% clear, 100% heartwood, and 100% vertical grain. These shingles are 

available in three lengths (16, 18, and 24 inches).d

No. 2 No. 2 grade can be used in various applications. This grade of shingle must have at least 10 

inches of clear wood (butt-end) on a 16-inch shingle, 11 inches on an 18-inch shingle, and 16 

inches on a 24-inch shingle. This grade allows no limitation on flat grain. Limited sapwood is 

also allowed in this grade. 

No. 3 No. 3 grade is a utility grade intended to be used on economy applications as well as on 

secondary buildings. This grade must have at least 6 inches of clear wood (butt end) on 16-inch 

and 18-inch shingles and 10 inches on a 24-inch shingle. 

No. 4 No. 4 grade is to be used for the under course of double-coursed sidewalls only. This shingle is 

never to be used for roof application or as a starter course on roofs 

aRefer to CSSB 97 for more information on grade rules for cedars and redwood. 

b Graded on the split side. 

c

Sawn on both sides and graded on one face. 

d

 1 inch = 25.4 mm. 

Figure 2. Example of shingle siding after many years of 

service. 
General Technical Report FPL–GTR–202

4

Figure 3. Certi-label western redcedar 

shakes. Used with permission from Cedar 

Shake and Shingle Bureau Exterior and Interior Wall Manual. 

Figure 4. Certigrade western redcedar 

shingles. Used with permission from Cedar 

Shake and Shingle Bureau Exterior and Interior Wall Manual. 

Table 2. Grade and description of shingles from northern white-cedar (Thuja occidentalis)

Gradea

 Descriptionb

Extra No defects are allowed in this grade. 

Clears No limitations on flat grain. Knots are allowed no closer than 7 inches from the butt-end.c Holes of 

1 inch in diameter allowed not closer than 8 inches from the butt. Rot is not allowed. Sapwood can 

be 3⁄4 inch wide not closer than 10 inches from the butt-end. Wane can be 3⁄4 inch wide not closer 

than 10 inches from the butt-end. 

Second Clears No limitations on flat grain. Knots must be sound with no restriction. Coarse or black knots may be 

a maximum of 1 inch in diameter not closer than 6 inches from the butt-end. Holes of 1 inch in 

diameter allowed not closer than 61⁄2 inches from the butt-end. Rot streaks not closer than 6 inches 

from the butt-end. Sapwood can be 11⁄2 inches wide not closer than 6 inches from the butt-end. 

Wane can be 3⁄4 inch wide not closer than 61⁄2 inches from the butt-end. 

Clear Walls No limitations on flat grain. Knots must be sound with no restriction. Course or black knots may 

be a maximum of 1/3 the width of the shingle but not closer than 6 inches from the butt-end. Holes 

of 1 inch in diameter allowed not closer than 6 inches from the butt-end. Rot streaks not closer 

than 6 inches from the butt-end. Sapwood, no restriction. Wane is allowed not closer than 6 inches 

from the butt-end. 

Utility No limitations on flat grain. All defects found in wood shall be permitted provided that the extent 

of the defects, singular or in combination, do not impair the use of the shingle. 

a

 Refer to Quebec Lumber Manufacturer’s Association (QLMA) for complete information on grades of eastern white-cedar. 

b

 All eastern white cedar grades contain flat grain. 

c One inch = 25.4 mm. 
Installation, Care, and Maintenance of Wood Shake and Shingle Siding

5

Specialty-Cut Shingles

Specialty-cut specialty shingles are cut 5 in. (127 mm) wide 

and come in 16- and 24-in. (406- and 610-mm) lengths 

with a variety of different butt-end designs (Fig. 6). Some 

examples are square, diamond, half-cove, octagonal, round, 

arrow, hexagonal, diagonal, and fish-scale butt-end designs.

Installation

The spacing between shakes and shingles depends on the 

grain angle, width of the shake or shingle, and moisture 

content at the time of installation. Flat-grained shakes and 

shingles shrink and swell almost twice as much as verticalgrained ones and require more space between them to avoid 

buckling (Fig. 7). Wide shingles require more space than 

narrow shingles. If the moisture content is low (5%–6%), 

leave a little extra space; if it is high (above 20%), decrease 

the spacing slightly. As a general rule for shingles equilibrated to ambient conditions (about 12% moisture content), 

shingles should be installed about 1/8 to 1/4 in. (3 to 

6 mm) apart whereas shakes should be spaced about 3/8 in. 

(9.52 mm) apart and not more than 1/2 in. (13 mm) apart. 

Adjacent courses should be offset at least 1 1/2 in. 

(38 mm). Shakes and shingles siding may be attached to 

exterior walls in a variety of ways.

Rain-Screen Method

The rain-screen method of building construction gives a 

secondary barrier and drainage plane for water (Fig. 8). 

Sheathing is placed over the studs and a water-resistant barrier (usually Type 30 felt) is applied. Although the shakes 

and shingles are not nailed directly to the sheathing in rainscreen applications, most codes still require plywood sheathing. Plywood sheathing transmits moisture better than OSB; 

therefore, if it gets wet, it dries more quickly. A variance to 

use OSB in a rain-screen application needs to be requested 

before installing the sheathing. Furring strips (nominal 1 by 

2 in. dimension lumber (19 mm by 38 mm)) or nominal 

2 by 2 in. dimensional lumber (38 mm by 38 mm) are 

placed over the building paper directly over each wall stud. 

The thickness of the furring strips or (2 by 2s) must be 

sufficient to avoid having the siding nails penetrate the

felt or house wrap. Horizontal boards (usually nominal 

1 by 4 in. dimensional lumber (19 mm by 89 mm)), spaced 

to coincide with the exposed shake or shingle length,

Figure 5. Newly installed shingle siding with transparent water-repellent preservative finish.

Figure 6. Specialty cut shingles: a, rebutted and rejointed shingles, 

machine grooved shingles; b, butt-end design. Used with permission from Cedar Shake and Shingle Bureau Exterior and Interior Wall 

Manual. 
General Technical Report FPL–GTR–202

6

are placed across the furring strips to give an open space 

between the backside of the shakes or shingle and the 

sheathing. The space is vented at the top and bottom and 

must be screened to keep out insects. The top may be vented 

directly into the soffit to connect the air-flow with the attic 

ventilation. Flashing must be installed around doors and 

windows just as with any siding system.

Note: There are two current ASTM designations for 

Type 30 felt depending on the area of the country. 

Where Type IV felt is required, it must meet ASTM 

D4869 standard; Type II felt must meet ASTM D226 

(Check with local code officials.). 

Direct Application

For direct application, shakes or shingles are applied directly over properly installed and flashed Type 30 felt (or house 

wrap as approved by local codes). Shakes and shingles 

may be single-coursed (Fig. 9), stagger-coursed (Fig. 10),

or double-coursed (Fig. 11). The double-course application 

permits the use of a lower grade for the first layer and a 

greater exposure of the higher quality second layer of shake 

or shingle. Pressure-impregnated preservative-treated products can be used in these applications.

Application Over Existing Siding

Shakes and shingles may be used to cover existing wood 

beveled siding, masonry, or stucco. The shakes or shingles 

can be applied directly over the existing siding; however, 

rain screen application is necessary over brick, stucco, and 

Figure 7. Buckling of shingles installed with insufficient gap.

Figure 8. Rain screen technique.

Figure 9. Single-coursed application of shingles. 

Used with permission from Cedar Shake and Shingle Bureau Exterior and Interior Wall Manual. 
Installation, Care, and Maintenance of Wood Shake and Shingle Siding

7

foam sheathing (Fig. 12). If applied directly over composite 

wood siding products such as hardboard siding, use longer fasteners and nail through the siding to the underlying 

sheathing. The brick molding around windows and doors 

will have to be extended, so it may be better to increase the 

wall thickness even more and use the rain-screen application. Fasten vertical furring strips to the underlying wallstuds, fasten horizontal boards to the vertical strips, and nail 

the shakes or shingles to the horizontal nailing strips. 

Note: Always check with the manufacturer of the product as well as with your local code official for approved 

application methods in your local area. Keep in mind 

that local codes often specify minimal requirements.

Fasteners

Nail placement for cedar shingles up to 10 in. (254 mm) 

wide requires two corrosion-resistant nails driven 3/4 in. 

(19 mm) from each edge and 1 in. (25 mm) above the exposure line. For shingles wider than 10 in. (254 mm), drive 

two additional nails approximately 1 in. (25 mm) apart near 

the center. To decrease the chance of splitting the shake/

shingle, fasteners should be blunted siding nails and should 

be ring-or twist-shank to improve holding. A ring-shank nail 

will have adequate holding power if it penetrates 3⁄4 in. 

(19 mm) into the wood. Corrosion-resistant nails are 

needed to avoid iron stains caused by extractives in the 

wood and corrosion by acid rain, salt air, etc. Certain

Figure 10. Stagger-course application. Used with permission from 

Cedar Shake and Shingle Bureau Exterior and Interior Wall Manual. 

Figure 11. Double-course application. Used with permission from 

Cedar Shake and Shingle Bureau Exterior and Interior Wall Manual. 
General Technical Report FPL–GTR–202

8

preservative- and fire-retardant treatments also may be 

corrosive. Check with the product supplier for recommendations on proper fasteners for their products. Non-corrosive 

siding-nails are available in hot-dipped galvanized (as per 

ASTM A 153/D) and type 304 or 316 stainless steel. Additional information may be available from supplier websites, 

and some suppliers may have additional requirements. 

Finishes

Finish Selection

Wide selections of oil- and latex-based finishes are available for shakes and shingles. Oil-based finishes are solventborne, and latex-based are water-borne; however, in recent 

years the solvent-borne finishes often have co-solvents in 

them to make them water soluble. As with any other wood 

product, shakes and shingles can be finished with waterrepellent preservatives (clear and lightly pigmented), 

semitransparent stains, solid-color stains, or paints.

Water-Repellent Preservatives

Water-repellant preservative (WRP) is a generic term that 

describes a clear penetrating finish that traditionally was 

formulated with about 10% to 20% oil or alkyd binder, 1% 

to 3% wax or similar water repellent, a preservative, and an 

organic solvent such as mineral spirits or turpentine. The 

finish does not contain a pigment and gives a natural wood 

appearance (Fig. 5). The low wax content in some of the 

traditional WRP formulations made it possible to use them 

for pretreatment of wood prior to painting. They were also 

an excellent pretreatment for shakes and shingles prior to installation. Bundles of shingles could be dipped. Most of the 

finish was absorbed into the end grain at the butt end of the 

shake or shingle and gave years of protection by minimizing 

end-grain water penetration. 

To meet stringent air quality requirements, these solventborne types of WRPs are no longer available. They have 

been largely replaced by waterborne formulations and formulations having low organic solvents content. Many of 

these formulations are intended for use on wood decks, but 

they can also be used on siding. These finishes often are 

tinted with a small amount of pigments, UV stabilizers, 

and other additives to improve their service life 

(Fig. 13). They give some water repellency and inhibit 

mold and algae growth on the lateral surface. If used on 

single-story structures having wide roof overhang, they

give about 2 to 3 years of service, depending on exposure. 

Semitransparent Stains

Semitransparent penetrating oil-based stains are similar to 

WRPs, but have considerably more pigments than WRPs 

(Fig. 14). As with WRPs, new semitransparent finishes are 

low in organic solvents and may not penetrate wood as well 

as traditional semitransparent stains. Semitransparent stain 

provides a color without entirely concealing the color, grain, 

and texture of the wood. Stains with the highest 

Figure 12. Rain screen technique over brick. Used with permission 

from Cedar Shake and Shingle Bureau Exterior and Interior Wall 

Manual.

Figure 13. Shingles treated with tinted water-repellent 

preservative.
Installation, Care, and Maintenance of Wood Shake and Shingle Siding

9

pigment concentration will provide the longest service life 

and provide the most protection from weathering. Some 

companies formulate stains especially for use on wood 

shakes and shingles. (Check the internet for “wood shingles 

and paint” to find leads on paint manufacturers having 

products for wood shakes and shingles.) Stains that contain 

a water repellant and wood preservative will provide additional protection and further extend the service life of your 

siding. Oil-based stains penetrate the wood and generally 

give longer service life than latex semitransparent stains 

do. Oil-based formulations degrade by slow erosion of the 

pigment from the surface and it is seldom necessary to do 

extensive surface preparation prior to refinishing. Latex 

semitransparent stains do not penetrate the wood but form a 

thin film on the surface. They tend to fail by flaking and may 

require extensive surface preparation prior to refinishing.

Paint manufacturers and resin suppliers are making progress 

to overcome these limitations.

Solid-Color Stains

Solid-color stains (also called solid-body stains or opaque 

stains) are available in oil- and latex-based formulations. 

They give more protection against UV radiation than semitransparent stains. However, solid-color stains do not penetrate wood; they form a film just as paints do. To get good 

service life, they need to have sufficient film thickness to 

avoid failing by flaking and peeling. Prior to application, 

it is best to prime shakes or shingles with a stain-blocking 

primer prior to applying a solid-color stain to avoid extractives bleed (Fig. 15). These stains perform best on textured 

or rough surfaces, but should not be used on a weathered 

surface (see Refinishing section).

Paint

Paint is a film-forming opaque finish and provides the best 

surface protection against water and weathering. Good 

quality stain-blocking primers applied to all surfaces prior to 

installation offer the best protection against discoloration by 

water-soluble extractives. (See discussion of back priming

in Factory Finishing section.) Top coat with good quality 

acrylic latex-based paint. As with solid-color stains, paints 

will not adhere to weathered surfaces.

Caution: The use of transparent film-forming finishes such 

as urethane varnish, lacquer, conventional varnish, and 

shellac are not recommended for exterior use. Ultraviolet 

(UV) radiation can penetrate these types of finishes and 

degrade the wood. The finish will become brittle, then develop cracks and peel from the surface. Paint manufacturers 

continue to improve the UV radiation resistance of these 

products. It may be possible to get 2 to 3 years of good performance with finishes formulated with some of these new 

products, particularly on structures having moderate protection from sunlight (single-story structures having wide roof 

overhangs and/or shaded by trees).

Finish Application

Factory Finishing

Factory-finished shakes and shingles are available and in recent years have become the preferred product in many areas 

of the country. Factory finishing offers several advantages 

over on-site finishing. Factory finishing eliminates weather 

limitations and avoids damage by UV radiation to the unpainted wood. Back priming (the application of finish to the 

back side of the shake) of shakes and shingles is easily done 

during factory application. Back priming decreases water 

absorption and extractives bleed. The primer should extend 

about half to two thirds up the back side of the shingle. If 

pre-finished shakes or shingles need to be trimmed during 

application, the cut surfaces should be touched up with 

finish.

Onsite Finishing

It is possible to finish shakes and shingles prior to installation. It is a rather labor-intensive process, but will improve 

Figure 14. Semitransparent stain application to shingles 

that were let weather for about two years. NOTE: The stain 

application was not done correctly. The painter allowed 

stain to partially coat the bottom of the course of shingles 

directly above the stained portion. When the shingles above 

are stained, there will be a lap mark.

Figure 15. Single coat of solid-color stain. Note the 

extractives bleed.
General Technical Report FPL–GTR–202

10

the performance of finishes on shake and shingle siding, 

particularly on structures having minimal roof overhang 

and on the sides of structures exposed to strong wind-blown 

rain. Finishing shakes or shingles prior to installation makes 

it possible to back-prime with a stain-blocking primer or 

penetrating stain.

As mentioned above, traditional WRPs could be dip-applied 

to shakes and shingles prior to application. Modern tinted 

WRPs and semitransparent stains contain pigments and 

should not be used to dip-treat shakes and shingles in bundles. The finish may not flow among the shakes or shingles, 

thus giving a blotchy appearance. If they are dipped, it 

should be done piece-by-piece, followed by brushing to 

work the finish into the wood. If shakes and shingles are 

unseasoned (green), WRPs and stains will not penetrate 

very well. 

Whether applying the finish prior to or following installation, select a top-quality finish recommended for use on 

cedar or redwood and follow the manufacturer’s recommendations for application (recommendations for proper wood 

moisture content and ambient temperature at the time of application). In general, finishes should not be applied to wood 

having a moisture content above 20%. The temperature 

during application and for 24 h following application should 

be above 40° to 50°F (depending on the manufacturer). 

Application instructions are usually stated on the label and 

additional information is available from the company help 

desk. The telephone number is usually listed on the label.

Note: For all types of finish, always follow the coating 

manufacturer’s application recommendations for their

particular product.

The most effective means for applying finishes to wood is 

by brush. Brushes are an investment and it is wise to purchase top quality brushes, as they will last for a long time 

if properly cared for. For latex-based finish, use a synthetic 

bristle brush; for oil-based finishes, use a natural-bristle 

brush. For best results, purchase long-bristle brushes. If you 

choose to apply the finish by spraying or with a roller, brush 

the surface (back brush) immediately after application.

Back brushing is essential to ensure that the finish is spread 

evenly and worked into the wood surface. Ensure that the 

butt-end gets a liberal application of finish; this is the most 

important surface. This is especially important for semitransparent stains and tinted WRPs. If using a roller, use 

natural roller covers for oil-based finishes and synthetic 

rollers for latex-based finishes.

For tinted WRPs and semitransparent stain application to 

installed shakes and shingles, it is necessary to take care to 

prevent lap marks (an area with two coats rather than one). 

Apply the finish in a single direction, usually across the 

structure, from a corner to a door, window, or other corner, 

keeping a wet edge throughout the application of this 

section. The lateral edges of the advancing strip of finish 

must coincide with the top and bottom edge of the course 

(s) of shake or shingle. When applying finish adjacent to the 

course that is already finished (the next strip), take care not 

to apply additional finish to the area that is already finished, 

as this causes a lap mark. For penetrating finishes such as 

WRPs, semitransparent stains, and to some extent solidcolor stains, lap marks give an unsightly blotchy appearance

(Fig. 16). The stain application shown in Figure 14 was not 

done correctly. The painter allowed the stain to partially 

coat the bottom of the course of shingles directly above the 

stained portion, creating a lap mark.

Maintenance 

Removal of Algae, Mold, and Iron Stains

Wood Surfaces

As wood ages, mildew (mold) and algae begin to grow on 

the surface. This is a normal process and these organisms 

do not degrade the wood; they cannot break down the 

structural components of wood. Although they can metabolize extractives in wood, they primarily feed off airborne 

contaminants. Because they do not attack the wood, 

removing them is a cosmetic issue: ignoring them will not 

damage the wood. Algae and molds can be cleaned quite 

easily and effectively with bleaching agents such as sodium 

Figure 16. An example of a lap mark from 

improper application of a semitransparent stain. 
Installation, Care, and Maintenance of Wood Shake and Shingle Siding

11

hypochlorite (liquid household bleach) or sodium 

percarbonate (the active ingredient in some commercial 

cleaners). Bleaching agents quickly kill mold and algae, but 

they also can degrade wood. Therefore, dilute cleaners as 

much as possible. The object is to remove the fungi without 

excessive wood damage.

We recommend using commercial cleaners containing sodium percarbonate or other oxygen bleaches because they 

are more gentle oxidizers than chlorine-containing bleaches 

such as household bleach. Chlorine bleaches may cause excessive pulping of the wood to give a fuzzy surface. Some 

commercial cleaners contain strong alkali (sodium hydroxide or potassium hydroxide). These ingredients help to 

remove residual finishes on the wood surface, but can cause 

even more surface damage than chlorine bleach.

When using a cleaner, you might mix the solution weaker 

than the recommended strength and try it on a small area. If 

the weaker solution doesn’t work, increase the concentration until you find a concentration that cleans the wood. A 

fuzzy surface appearance or excessive removal of surface 

fibers indicates that the solution concentration is too strong. 

Apply cleaning solutions with a garden-type sprayer, sponge 

mop, or soft bristle brush and keep the surface wet with 

the cleaning solution for 12 to 15 min. It is best to work 

on a cool, cloudy day or even during a gentle rain so the 

solution doesn’t evaporate. Aggressive scrubbing shouldn’t 

be necessary; let the cleaner do the work. Rinse with a garden hose keeping the water-stream pointed down to avoid 

forcing water behind the courses of shakes or singles. High 

pressure shouldn’t be necessary. Allow the surface to dry for 

several days before refinishing.

We recommend using commercial cleaners, but if you prefer 

to use liquid household bleach, start with a cleaning solution having about five parts warm water, one part bleach, 

and a small amount of powdered detergent. Do not use 

detergent that contains ammonia. Ammonia reacts with 

bleach to form toxic fumes. If the surface mildew is difficult 

to remove, try using a stronger solution of three or four parts 

water added to one part bleach and detergent. It should not

be necessary to use a concentration stronger than three to 

one.

If the dilute cleaning solutions described above are not effective, it is probably because the mildew has inter-grown 

with residual finish on the surface. The residual finish is 

keeping the cleaning solution away from the mildew. In this 

situation, it may be necessary to use aggressive cleaning 

methods, such as the cleaners containing strong alkali. In 

extreme cases, it may be necessary to use a paint stripper to 

remove the residual finish prior to cleaning.

As with unfinished wood, wood finished with WRPs and 

semitransparent stains degrades as these finishes degrade. 

Ultraviolet radiation in sunlight degrades lignin at the 

surface. Lignin is the natural glue in wood that holds the 

cellulose fibers in place. Degradation of lignin weakens 

the surface fibers, and strong cleaning solutions and aggressive methods will remove excessive amounts of fiber 

from the surface. Removing these fibers is detrimental 

to the performance of subsequent application of WRPs

or semitransparent stains. These finishes perform best by 

penetrating the wood surface; as a wood surface degrades, 

it becomes more porous. If excessive amounts of fiber are 

removed during cleaning, the surface will not accept these 

finishes as well as the porous weathered surface. Again, 

when cleaning wood, the gentler the better.

Iron reacts with the some of the extractives in cedar and 

redwood to give a dark blue-black stain. This often occurs 

when the zinc on galvanized fasteners weathers away. Use 

only hot-dipped galvanized fasteners that meet ASTM 

A153/D or type 304 or 316 stainless steel that meet ASTM 

A276. Shakes and shingles can also be contaminated with 

rust washed from other sources such as window screens, 

failed flashing, or metal ornaments. A 5% solution of oxalic

acid (usually available at drugstores) neutralizes this blueblack stain.

Note: Oxalic acid is toxic. Many commercial wood cleaners 

contain oxalic acid, which neutralizes iron stains and removes extractive stains. Oxalic acid generally brightens 

wood surfaces, but is not very effective for removing algae 

or mold, nor will it keep iron stain from reoccurring if the 

source of the iron is not removed. 

Finished Surfaces

Finished surfaces (paints, semitransparent stains, and solidcolor stains) often develop mold and algae. As with wood 

surfaces, these microorganisms feed off airborne contaminates, but can also metabolize oils in some finishes. Surfaces 

of paint and solid-color stain can easily be cleaned with 

commercial cleaners or a dilute solution of household bleach

and as with wood, the gentler the better. Abrasive methods 

will damage the finish surface. It is more difficult to remove 

these microorganisms from saw-textured wood; the microorganisms may be inter-grown through and under the finish.

Refinishing

WRPs and Semitransparent Stains

Other than mold removal and gentle washing, WRP and 

semitransparent stains should not require additional surface 

preparation. They can be reapplied as soon as shakes or 

shingles are dry following cleaning. The reapplication of 

semitransparent stains and tinted WRPs requires special 

care. Usually residual finish is left in some areas, whereas 

the finish may be completely weathered away in other areas. 

The weathered and unweathered surfaces accept penetrating 

stains differently; the weathered areas absorb stain easily,

whereas stain forms a second coat on areas having residual 

stain. During application, feather the stain into areas having 

old finish to avoid forming this second coat. If a second coat 
General Technical Report FPL–GTR–202

12

is formed, it will give a shiny appearance and will fail by 

flaking. When refinishing a structure, it is often necessary 

to have the north, east, west, and south sides on different 

cycles. Semitransparent stains usually last 4 to 5 years on 

the south side and more than 10 years on the north side. 

These estimates can vary considerably depending on the 

design of the structure, exposure conditions, and the quality of the shake or shingle. As with the application for new 

construction, take care to avoid lap marks. Changing colors 

or switching to a paint or solid-color stain is not an option 

with semitransparent stains unless the old finish and weathered surface is removed. The surface must be scuff-sanded, 

primed, and finished (at least two coats may be required to 

hide residual stain). 

Solid-Color Stains

When reapplying solid-color stain, wash the surface to 

remove dirt and mold. If areas have peeled exposing the 

wood surface, the weathered surface must be removed prior 

to re-priming the peeled area (Fig. 17). Figure 17 shows an 

extreme case of surface degradation following the failure of 

the coating. Solid-color stains form films, and like all other 

film-forming finishes, do not bond properly to weathered

wood. It has been well established through several studies 

that cedar exposed to sunlight for as little as 2 to 3 weeks 

will not hold film-forming finishes as well as an unweathered surface. It may be possible to remove the damaged 

wood from small areas by scuff sanding, but this is difficult 

with shakes and shingles because the surfaces are saw-textured or split. The sanded surface won’t match the unsanded 

surface. If the previous finish contained lead, do not sand.

(See section on lead paint.) 

The situation shown in Figure 17 is an extremely difficult 

problem to reconcile. A penetrating finish, such as an 

oil-based semitransparent stain, cannot be used over the 

existing finish, and a film-forming finish will not adhere to 

the weathered surface. It is probably necessary to remove 

all the finish and the weathered surface by power washing 

prior to application of the primer and solid-color stain. (See 

section on lead paint.) This may be one of the few instances 

where careful power washing by a skilled operator is necessary. As with using a garden hose to wash siding, keep the 

nozzle pointed down to avoid forcing water behind the 

siding.

Paints

Refinish in the same way as solid-color stains. Lap marks 

should not be a problem with paint systems.

Lead Paint—Prior to about 1985, many paints used 

on wood structures contained lead. Do not sand these 

surfaces. Dust containing lead can contaminate the 

interior of the structure causing severe health problems 

and can even be fatal. Dust from lead-containing paint 

is extremely toxic. All lead paint removed from a 

structure must be treated as hazardous waste and be 

disposed of in accordance with federal, state, and local 

regulations. Some areas may require a certified specialist to remove paint containing lead pigments.

Safety Precautions

It is best to apply cleaners on a cloudy day. This slows 

evaporation and allows the cleaner to work more effectively. 

Wear eye protection, rubber gloves, an apron, boots, and 

other protective gear when using and preparing cleaning

solutions. Avoid getting cleaning solutions on yourself, 

other parts of the structure, and vegetation. If the cleaning solution comes in contact with you or these other areas, rinse promptly and thoroughly with water. Follow all 

additional instructions on labels and technical data sheets 

supplied by manufacturers of cleaning products and finishes.

In the rare case that pressure washing of shakes and shingles 

is necessary, it should be done only by contractors having 

experience cleaning cedar. In the wrong hands, high-pressure water can easily remove an excessive amount of wood 

fiber, which could drastically decrease the life expectancy 

of your shakes and shingles.

Other Sources of Information

Cedar Shake and Shingle Bureau 

P.O. Box 1178

Sumas, WA 98295-1178

604-820-7700

www.cedarbureau.org

USDA Forest Service

Forest products Laboartory

One Gifford Pinchot Drive

Madison, WI 53726-2398

608-231-9200 

www.fpl.fs.fed.us

Figure 17. Severely weathered wood surface.
Installation, Care, and Maintenance of Wood Shake and Shingle Siding

13

Copper Development Association

P.O. Box 144

Pocopson, PA 19366-0144

800-232-3282

www.copper.org

American Society for Testing and Materials (ASTM)

100 Barr Harbor Drive

West Conshohocken, PA 19428-2959

610-832-9585

www.astm.org

Maze Nails

100 Church Street

Peru IL 61354

800-435-5949

www.mazenails.com

Swan Secure Products, Inc.

7525 Perryman Court

Baltimore, MD 21226

800-966-2801

www.swansecure.com