Installation, Care, and 

Maintenance of Wood 

Shake and Shingle Roofs

Tony Bonura

Jack Dwyer

Arnie Nebelsick

Brent Stuart

R. Sam Williams

Christopher G. Hunt

United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

General

Technical

Report

FPL–GTR–201
October 2011

Bonura, Tony; Dwyer, Jack; Nebelsick, Arnie; Stuart, Brent; Williams, R. 

Sam; Hunt, Christopher G.; 2011. Installation, Care, and Maintenance of 

Wood Shake and Shingle Roofs. General Technical Report FPL-GTR-201. 

Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.11 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 

of an individual’s income is derived from any public assistance program. 

(Not all prohibited bases apply to all programs.) Persons with disabilities 

who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET 

Center at (202) 720–2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence 

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.

Authors are members of the Joint Coatings Forest Product Committee. The 

American Coatings Association and the Forest Products Laboratory cosponsor 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. Tony Bonura chaired the 

task group and he is the author to contact for more information. (Mr. 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).

Abstract

This article gives general guidelines for selection, 

installation, finishing, and maintenance of wood shake 

and shingle roofs. The authors have gathered information 

from a variety of sources: research publications on wood 

finishing, technical data sheets from paint manufacturers, 

installation instructions for shake and shingle roofs, and 

interviews with experts having decades of experience in 

constructing and inspecting shake and shingle roofs. Where 

possible, recommendations are based on research results;

however, some information is determined from practical

experience installing shake and shingle roofs. More detailed 

information is available from shake and shingle suppliers

and the Cedar Shake and Shingle Bureau (CSSB). Note: 

Installation instructions contained herein are not intended to 

supercede local building codes.

Keywords: Shakes, shingles, ultraviolet radiation, UV 

degradation, water-repellent preservatives, semitransparent 

stains, solid-color stains, paints

Safety Precautions

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

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 instruction on labels and technical data sheets 

supplied by manufactures of cleaning products and finishes.

Acknowledgments

We thank Martin Obando for reviewing the manuscript and 

giving us suggestion on general practices used in the field 

for installing shakes and shingles.

Contents

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

Product Selection ..............................................................1

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

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

Installation.........................................................................4

 Spaced Sheathing..........................................................4

 Solid Deck Sheating......................................................6

 Rain-Screen...................................................................6

 Horizontal Nailing Strips..............................................7

 Direct Application.........................................................7

Fasteners ...........................................................................8

Zinc or Copper Strips........................................................8

Finish Selection and Application ......................................8

 Water-Repellent Preservatives......................................8

 Semitransparent Stains..................................................9

 Factory Finishing ..........................................................9

 On-Site Finishing..........................................................9

Maintenance......................................................................9

 Cleaning ..................................................................... 10

 Refinishing ................................................................. 10

Other Sources of Information ........................................ 10

The Cedar Shake and Shingle Bureau (CSSB) is a 

nonprofit organization that oversees the inspection 

of western redcedar (Thuja plicata), Alaska yellowcedar (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 periodic thirdparty 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.
Installation, Care, and Maintenance 

of Wood Shake and Shingle Roofs

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

Jack Dwyer, State of Vermont, retired

Arnie Nebelsick, Edmund Allen Lumber Company, Momence, Illinois

Brent Stuart, Russin Lumber Corporation, Vancouver, British Columbia, Canada

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

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

Introduction

Western redcedar (Thuja plicata), Alaska yellow-cedar 

(Chamaecyparis nootkatensis, also called yellow cedar), and 

redwood (Sequoia sempervirens) are the wood species most 

commonly specified by architects and are included in building codes for the USA and Canada. To meet these building 

code requirements, shakes/shingles must meet wood quality 

standards, which are verified through third party inspections (Table 1). Other species have historically been used for 

shakes/shingles: northern white-cedar, also known as eastern white cedar (Thuja occidentalis) (Table 2), white oak 

(Quercus alba), and Southern Pine (also called southern yellow pine (Pinus spp.)). The quality of northern white-cedar, 

white oak, and Southern Pine shakes/shingles is not assured 

through CSSB inspection. Therefore, check local building 

codes for compliance before using these species on residential or commercial roofs. The exception to this code requirement may be use of these species for historical restoration.

Wood shakes and shingles have been used for centuries as 

a roofing material. Asphalt, steel, and polymeric materials 

are newcomers. If properly installed and maintained, wood 

shakes and shingles should last more than 30 years (Fig. 2).

Product Selection

The first requirement for long service life is the selection 

of the shake or shingle. These products are available in 

a range of grades and are described in Table 1 (listed in 

order of decreasing quality). This is where “money talks!”

The higher the grade (and price), the longer the roof can 

be expected to last. Shakes and shingles that contain only 

heartwood are more resistant to decay than are shingles that 

contain sapwood. Vertical-grain (or edge-grain) shakes and 

shingles will perform better than flat-grain grades; verticalgrain wood is more dimensionally stable and therefore less 

likely to warp and split. Narrow shakes and shingles are less 

likely to warp than wide ones. Thicker shakes and shingles 

are less likely to warp than are thinner ones. Also, check 

with your local building code official because some localities often have additional requirements (for example, 

fire-retardant or preservative treatment).

Shakes

Split shakes differ from sawn shakes and shingles in that 

the side to the weather is a split surface, and therefore the 

wood cells are aligned with the surface of the shake. This 

gives a lateral surface with minimal cut wood cells and thus 

decreases water penetration into this surface. Shingles and 

tapersawn shakes are sawn to give a uniform surface, but in 

the process, the surface fibers are cut, increasing the chance 

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. Straight-split 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 in.).d

No. 2 No. 2 grade can be used in various applications. This 

grade of shingle must have at least 10 in. of clear wood 

(butt end) on a 16-in. shingle, 11 in. on an 18-in. 

shingle, and 16 in. on a 24-in. 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 in. of clear 

wood (butt end) on 16-in. and 18-in. shingles and 10 in. 

on a 24-in. 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. 

a

Refer 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 in. = 25.4 mm.
General Technical Report FPL–GTR–201

2

for water penetration. Shakes come in a variety of sizes, 

shapes, and surfaces. 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). Tapersawn shakes are commonly available having 

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

22 mm) and may be special ordered up to 2 in. (51 mm) 

butt-end thickness. All shakes are available in two grades 

(Premium and No. 1) and are graded to one face according to the grain angle, flaws, and amount of heartwood/

sapwood. A brief description of each grade is contained 

in Table 1 and Figure 3a. Additional information on grade 

is readily available on the Cedar Shake & Shingle Bureau 

website (www.cedarbureau.org). Click the Products, Codes 

and Testing tab and then click Shakes. Click the appropriate 

shake or shingle and then click Grading Rules. There are 

three rules for three different types of shakes and three rules 

for three different shingles. You will see the drop-down for 

the CSSB-97 Grade Rules. 

Shingles

Shingles are similar in appearance to tapersawn shakes except that they are thinner. Whereas the minimum butt-end 

1 The 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. 

thickness for tapersawn shakes is at least 5/8 in. (16 mm), 

shingles have a butt-end thickness of about 3/8 to 1/2 in. 

(10–13 mm). Western redcedar, 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: No. 1, No. 2, No. 3, and No. 4 (Fig. 3b, Table 1). 

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

and 100% vertical grain. Lower grades may contain sapwood, flat grain, and knots. Lengths may be 16, 18, or 24 in. 

(406, 457, or 610 mm). Thickness of shingles is described 

as the number of shingles per the total of butt-end thickness of that number of shingles. 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 end. That is, the total buttend thickness of 4 shingles must be at least 2 in. (51 mm). 

An 18-in. by 5/21⁄4-in. (457-mm by 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. (57 

mm). A 16-in. (406-mm) shingle is referred to as a “5X” 

because they are installed with a maximum 5-in. exposure. 

They are a 5/2-in. shingle; butt-end thickness of 5 shingles 

must be at least 2 in. (51 mm). Shingles are available in 

specified widths or random widths (Fig. 4).

Local code jurisdictions may have requirements for the 

grade of shake or shingle permitted for roof application in 

your area and special requirements, such as fire-retardanttreatments. Only Premium and No. 1 grades of shakes and 

No. 1 grades of shingles are pressure-impregnated with 

Table 2—Grade and description of shingles from northern white-cedara

Gradeb

 Descriptionc

Extra No defects are allowed in this grade. 

Clears No limitations on flat grain. Knots are allowed no closer than 7 in. 

from the butt end.d

 Holes of 1 in. in diameter allowed, not closer 

than 8 in. from the butt. Rot is not allowed. Sapwood can be 3/4 in. 

wide, not closer than 10 in. from the butt end. Wane can be 3/4 in. 

wide, not closer than 10 in. 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 in. in 

diameter, not closer than 6 in. from the butt end. Holes of 1 in. in 

diameter allowed, not closer than 6 1/2 in. from the butt end. Rot 

streaks not closer than 6 in. from the butt end. Sapwood can be 

1 1/2 in. wide, not closer than 6 in. from the butt end. Wane can be 

3/4 in. wide, not closer than 6 1/2 in. 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 one-third 

the width of the shingle, but not closer than 6 in. from the butt end. 

Holes of 1 in. in diameter allowed, not closer than 6 in. from the butt 

end. Rot streaks not closer than 6 in. from the butt end. Sapwood, no 

restriction. Wane is allowed not closer than 6 in. 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

Thuja occidentalis. b

Refer to Quebec Lumber Manufacturer’s Association (QLMA) for complete information on 

grades of eastern white-cedar. 

c

All eastern white-cedar grades contain flat grain. 

d

1 in. = 25.4 mm. 
Installation, Care, and Maintenance of Wood Shake and Shingle Roofs

3

fire retardants to meet Class A, B, and C fire requirements.

Other grades are not. Spray-on fire-retardant treatments are 

also available, but their effectiveness is not guaranteed by 

any inspection agency because the treatment may wash out 

by rain. There may also be requirements for preservative 

treatments. Only Premium and No. 1 grades of shakes and 

No. 1 grades of shingles may be pressure-impregnated with 

preservative treatments. Factory impregnation of shakes 

and shingles with preservatives such as chromated copper 

arsenate (CCA) can dramatically extend the life of shakes 

and shingles, especially in areas where warm temperatures 

and humid conditions are present for substantial parts of the 

year. Non-pressure treatments such as copper-8-quinolate 

and copper napthenate are also available, but these are not 

as leach resistant as pressure-applied preservatives. 

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 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 squarefeet and recommended exposure; 15) Application instruction on reverse side. 

Used with permission from Cedar Shake & Shingle Bureau, New Roof Construction Manual.

Figure 2. Example of shingle roof after decades of service. 
General Technical Report FPL–GTR–201

4

Installation

Shakes and shingles can be installed on roofs over spaced 

sheathing or solid deck sheathing. Various installation methods are described below. Spaced sheathing or rain-screen 

systems are common in geographic regions that experience 

high humidity. Direct application of shakes and shingles to 

solid sheathing is common in dry/arid regions. However, 

shakes require a solid plywood deck in geographical regions 

that experience wind-driven snow. In addition, check with 

local building codes for deck type requirements in highwind- or hurricane-prone areas. For all these methods, the 

spacing between shakes/shingles depends on the grain angle, 

the width of the shake/shingle, and the moisture content at 

the time of installation. Flat-grained shakes/shingles shrink 

and swell almost twice as much as vertical-grained ones and 

require more space between them to avoid buckling 

(Fig. 5). 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 1⁄4 to 3/8 in. (6–10 mm) apart, 

whereas shakes should be spaced at least 3/8 in. 

(10 mm) apart and not more than 5/8 in. (16 mm) apart. 

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

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

in a variety of ways.

Spaced Sheathing

Spaced sheathing is the traditional roof system used for 

shakes and shingles. Shakes or shingles are attached to 1 by 

4 in. (19 by 89 mm) or 1 by 6 in. (19 by 140 mm) boards 

placed horizontally across the rafters (Fig. 6). Note that 

1 by 4 and 1 by 6 are nominal sizes and hereafter will be 

referred to as 1 by 4 or 1 by 6 boards. The boards are spaced 

on centers equal to the recommended exposed surface of the 

shake or shingle. A well-ventilated attic allows the back side 

of the shakes/shingles to dry, which generally improves their

performance. 

NOTE: The installation of shakes (split shakes, and 

tapersawn shakes) and shingles is different. Shakes (split 

and tapersawn) can be installed in two- or three-ply applications. For two-ply application, shakes (split and tapersawn) 

Figure 3a. Certi-Label western redcedar shakes. Used 

with permission from Cedar Shake & Shingle Bureau,

New Roof Construction Manual.

Figure 3b. Certigrade western redcedar shingles. Used 

with permission from Cedar Shake & Shingle Bureau, New 

Roof Construction Manual.
Installation, Care, and Maintenance of Wood Shake and Shingle Roofs

5

must be interlaid with Number 30 felt (See text box) to decrease the infiltration of windblown rain and snow (Fig. 6). 

For three-ply application, split shakes require felt interlay; 

however, tapersawn shakes do not. A layer of felt is installed 

with each course of shake. The bottom of the felt should be 

placed above the butt-end of the shake at a distance equal to 

double the weather exposure. For example, if the exposure 

of an 18-in. shake is 7 1⁄2 in. (190 mm), the bottom of the felt 

should be 15 in. (381 mm) from the bottom of the shake. 

This means only the top 3 in. (76 mm) of the shake should 

be covered by the felt. Flashing must be installed just as 

with any roof system. Refer to page 20 of the Roof Manual 

found in the CSSB website under “installation and maintenance” for additional information on 

requirements for two- and three-ply shake installation. 

Shingles must be installed in a three-ply application and are 

not interlaid with felt as this impedes drying of the shingle,

thus decreasing the service life (Fig. 7). Interlaying shingles 

with felt will cause them to rot (“rot-felting”). The smooth 

surface of the shingle or three-ply application of tapersawn 

shakes makes a tight seal with the felt between each course 

of shingle, which does not permit the shingles to dry if 

water gets beneath them.

NOTE: The amount of asphalt in building felt 

(and hence its water repellency) is described by the 

weight per square (10 ft by 10 ft (about 3 by 

3 m)). Traditionally, this coverage of felt weighed 

30 pounds, hence the name 30-lb felt. This is no 

longer the case. The general category is now referred 

to as Number 30 felt. Within Number 30 felt are 

various “types” as specified by ASTM Standards D 

226 and D 4869. Section R905.9.2 of the International 

Residential Code specifies Number 30 felt for wood 

roofing material.

Figure 4. Thirteen-year-old shingle roof with random-width 

shingles.

Figure 5. Buckling of shingles installed with insufficient 

space between adjacent shakes/shingles to accommodate 

swelling.

Figure 6. Two-ply shake roof over spaced sheathing showing interlaid 

Number 30 felt. Used with permission from Cedar Shake & Shingle Bureau,

New Roof Construction Manual.
General Technical Report FPL–GTR–201

6

Solid Deck Sheathing

Rain screen, horizontal-nailing strips, and direct application 

are three common methods for installing shakes and shingles over solid sheathing. In modern construction, plywood 

is placed over the rafters to give solid deck sheathing. We 

recommend at least 3⁄4 in. (19 mm) thick plywood to ensure

proper nail holding. Local building codes for plywood thickness may allow a lesser thickness, but this is counter to best 

practices as specified by the CSSB. Solid deck application is 

recommended for shake application in areas that experience 

high winds or wind-driven snow and may be a local code 

requirement in these areas. Where solid deck sheathing is 

required, we recommend using the rain-screen technique 

or horizontal nailing strips. This ventilation between the 

shakes/shingles and the plywood sheathing improves performance. When shakes or shingles are installed directly on 

the sheathing in geographical regions having high humidity, 

they need to be preservative treated.

NOTE: There are two reasons for using plywood 

sheathing instead of oriented strandboard (OSB) 

for shake and shingle roofs. Plywood gives better 

nail holding than OSB and also has better moisture 

transmission properties. If plywood gets wet, the 

water is distributed over a larger area than with OSB. 

Plywood has a higher permeability to water vapor 

and thus dries more quickly than OSB.

Rain-Screen

The rain-screen technique simulates traditional roof systems

by allowing the back side of shakes or shingles to dry

(Fig. 8). The rain screen gives an air space between the back 

side of the siding and the plywood sheathing and possibly 

a secondary barrier to water. Sheathing is placed over the 

rafters. Although the shakes/shingles are not being nailed 

directly to the roof sheathing in a rain-screen application, 

local codes usually still require plywood or solid lumber 

sheathing. “Vertical” spacers (usually 2 by 4s) are placed 

directly over each rafter and are fastened securely through 

the sheathing to the rafters. Horizontal boards (nailing 

strips) 1 by 4 or 1 by 6 are placed across the 2 by 4 spacers 

to give an open space between the back side of the shakes or 

shingles and the solid roof deck. Use stainless steel or hotdipped galvanized screws of sufficient length to penetrate 

well into the underlying rafter to attach the “vertical” 2 by 4 

spacers. Attach the horizontal nailing strips securely to the 

“vertical” strips with screws. The space can be vented at the 

roof peak and at the fascia and must be screened to keep out 

insects. When using this solid deck technique for roof slopes 

less than 4:12 for shakes and 3:12 for shingles, a “hot mop”

or similar code-approved membrane is required over the 

sheathing.

As with spaced sheathing described above, two-ply or threeply handsplit shake and two-ply tapersawn shake installations require interlaid felt (Fig. 8). However, do not interlay 

shingles with felt as this impedes drying and decreases

service life (Fig. 9). 

Figure 7. Shingle roof over spaced sheathing. Used with permission from Cedar 

Shake & Shingle Bureau, New Roof Construction Manual.
Installation, Care, and Maintenance of Wood Shake and Shingle Roofs

7

Horizontal Nailing Strips

Apply 1 by 4 or 1 by 6 nailing strips horizontally directly 

to plywood sheathing. A decay-resistant species should be 

used for the nailing strip. The nailing strips are spaced at a 

distance equal to the exposed surface of the shake or shingle. Although this system does not have as much venting as 

the rain screen, the space between the shakes or shingles and 

the sheathing helps the roof stay dry. 

Direct Application

Shakes and shingles may be attached directly to roof sheathing. Whereas shingles must be three-ply application, shakes 

may be a two- or three-ply application. Handsplit, straightsplit, and tapersplit shakes must be installed with an 18-in. 

wide Number 30 felt interlay to improve protection against 

wind driven snow and rain (Fig. 10). However, do not 

interlay felt with shingles or a 3-ply application of Premium 

and No. 1 grades of tapersawn shakes unless required by 

a local building code. Two-ply application of tapersawn 

shakes must have felt interlay. 

CCA-treated shakes and shingles are required for direct 

shingle application to solid decks. CCA-treated sheathing is 

not required. This method does not have a secondary water 

barrier; therefore, when the roof begins to leak at the end of 

its service life, the sheathing is likely to decay. We do not 

consider direct application of shingles and tapersawn shakes 

to sheathing as robust as other roof systems. 

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.

Figure 8. Rain screen installation of shakes over solid sheathing. Used with permission from Cedar Shake & Shingle Bureau, New Roof Construction Manual.

Figure 9. Rain screen installation of shingles over solid sheathing. Used with permission from Cedar Shake & Shingle Bureau, New Roof Construction Manual.
General Technical Report FPL–GTR–201

8

Fasteners

Fasten shakes and shingles using corrosion-resistant ringshank nails having blunt tips. Consult with fastener manufacturers for the best fastener. Fasteners manufactured for 

asphalt shingles are not appropriate for wood shakes or 

shingles. Fasteners must be hot-dipped galvanized as per 

ASTM A 153/D or stainless steel (Type 304 or 316). Place 

nails 3/4 in. (19 mm) (from each edge and 1-1⁄2 in. (38 mm) 

above the exposure line. The head of the fastener should be 

flush with the surface of the shake or shingle. Do not overor underdrive the fasteners. Overdriving causes spalling, in 

which wood on the back side of the shingle detaches from 

the rest of the shingle. Corrosion-resistant nails are needed 

to avoid irons stains caused by extractives in the wood and 

corrosion by acid rain, salt air, etc. Certain preservativeand fire-retardant treatments may be corrosive. Contact the 

preservative or fire-retardant manufacturer for additional 

requirements for corrosion resistance of fasteners for use 

with their products.

Zinc or Copper Strips

Interlaying a zinc or copper strip at the ridge cap/vent can 

be effective for controlling the surface growth of algae, 

mold, and moss for a short distance down the surface of the 

roof. Some literature specifies 12 feet (4 m) between zinc 

or copper strips, however, this spacing may be inadequate; 

excessive spacing gives inconsistent protection causing a 

striped appearance. Recent experience shows that the spacing needs to be about 6 ft (2 m). Shakes and shingles below 

galvanized flashing around a chimney often have little algae 

or mildew because of the small amount of zinc eroding from 

the galvanized steel and washing down the roof. 

For complete details on shake/shingle installation 

consult the “New Roof Construction Manual” at the 

CSSB website (www.cedarbureau.org), the product 

manufacturer, and local building code officials. Local 

codes may have additional requirements to those 

described above.

Finish Selection and Application 

Because western redcedar, Alaska yellow-cedar, and redwood are naturally durable, applying a finish is not mandatory. Sometimes wood roofs are finished to preserve the color of shakes or shingles on the roof. This section provides 

information on various types of finishes and the application 

of those finishes. Always consult the particular finish manufacturer for information regarding the specific application 

criteria for their product and if their product is suitable for 

wood roof application.

Water-Repellent Preservatives

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

describes a clear penetrating finish that traditionally was formulated with about 10–20% oil or alkyd binder, 1–3% wax 

or similar water repellent, a preservative, and an organic 

solvent such as mineral spirits or turpentine. They were an 

excellent pretreatment for shakes/shingles prior to installation. Bundles of shakes/shingles could be dipped. Most of 

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

the shake/shingle and gave years of protection minimizing 

end-grain water penetration. To meet stringent air quality 

requirements, these 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 be used on roofs. These finishes often 

are tinted with a small amount of pigments, UV stabilizers, 

and other additives to improve their service life. Shakes 

and shingles should not be dipped in the tinted products 

in bundles because the pigments in them do not distribute 

evenly. If tinted products are used, it is necessary to dip 

them individually and back-brush to ensure even application 

and appearance. They give some water repellency and inhibit mold and algae growth. They give about 1–2 years of 

service on the exposed surfaces, but will decrease end-grain 

water absorption for many years and thus increase the life of 

the shake or shingle. This end-grain protection is more important than the 1–2 year protection that is obtained on the 

Figure 10. Installation of shakes directly on solid sheathing with interlaid 

Number 30 felt. Used with permission from Cedar Shake & Shingle Bureau, 

New Roof Construction Manual.
Installation, Care, and Maintenance of Wood Shake and Shingle Roofs

9

exposed surfaces where the WRP merely decreases mildew 

growth.

Semitransparent Stains

Semitransparent penetrating oil-based stains are similar 

to WRPs, but have considerably more pigments. As with 

WRPs, recently formulated semitransparent finishes are low 

in organic solvents and may not penetrate wood as well as 

traditional solvent-borne semitransparent stains. Semitransparent stain provides a color without entirely concealing the 

grain and texture of the wood. Stains with the highest 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 under “wood shingles and 

paint” to find leads on paint manufacturers having products 

for wood shakes and shingles. Stains that contain a waterrepellent and wood preservative will provide additional protection and further extend the service life of your roof. As 

with water-repellent preservatives, oil-based stains penetrate 

wood; they degrade by slow erosion of the pigment from 

the surface. It is seldom necessary to do extensive surface 

preparation prior to refinishing. 

As with tinted WRPs, the best way to apply a solvent-borne 

semitransparent stain is by dipping them prior to installation. Immerse the shake or shingle individually at least twothirds of its length, measured from the butt-end, back-brush 

following dipping, then stand them vertically or hang them 

from a line until they are dry. Back-brushing helps work the 

finish into the wood surface. If shakes or shingles need to 

be trimmed during application, the cut surfaces should be 

touched up with finish.

Film-forming finishes should not be used on roofs because 

they trap moisture in the wood, thus decreasing the life of 

the shake or shingle. Higher moister contents in the wood 

over longer times will increase the chance of wood decay. 

Film-forming finishes include paint, solid-color stains, 

latex semitransparent stains, and varnish. These finishes 

will crack and peel within a few years, giving an unsightly 

appearance. Consult with the particular finish manufacturer 

to ensure that their product is suitable for wood roof 

application.

NOTE: As mentioned previously, the wood cells of split 

shakes are aligned parallel with the surface. There are few 

cut cells to accommodate penetration of the finish; therefore, 

semitransparent stains last about 1—2 years on the lateral 

surfaces of split shakes. However, they will absorb into 

the end grain and give years of protection against water 

absorption. 

Factory Finishing

Factory finished shakes and shingles are available, but only 

those having penetrating finishes should be used on roofs. 

Shakes and shingles having other finishes such as 

solid-color stains are intended for use on side walls. Penetrating finishes are water-repellent preservatives (WRPs) 

and oil-based semitransparent stains. As mentioned above, 

latex semitransparent stains, solid-color stains, and paints 

form films and should not be used on roofs because they 

trap moisture in the wood and decrease the service life of 

the roof. 

Factory finishing offers several advantages over on-site 

finishing. Factory finishing avoids the need for workers 

to walk on the roof after it is installed. The back side and 

end grain of shakes and shingles are easily finished along 

with the front side. Finish on the back side decreases water 

absorption and extractives bleed. The finish should extend 

about half to two-thirds up the back side of the shake or 

shingle. Factory finishing eliminates weather limitations and 

avoids damage by UV radiation to the unfinished wood. If 

pre-finished shakes or shingles need to be trimmed during 

application, the cut surfaces should be touched up with 

finish.

On-Site Finishing

On-site finishing can be done prior to placing the shakes/

shingle on the roof or after the roof is complete. Finishing 

prior to installation makes it possible to back-prime the 

shakes/shingles, but it is more labor-intensive than finishing 

following installation. The disadvantage to finishing following installation is possible damage to the roof during finish 

application. Take care to avoid unnecessary walking on the 

roof. Apply liberal amounts to the shake/shingle by brush 

and strive to get the finish to absorb into the end grain.

When applying tinted WRPs and semitransparent stains 

following installation, it is necessary to prevent lap marks. 

Apply the finish in a single direction, usually across the 

roof from one side to the other 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 a shake or shingle. When applying finish 

adjacent to the area that is already finished (the next strip), 

take care not to apply additional finish to the area that is 

already finished. This causes a lap mark (an area with two 

coats rather than one coat of finish) and gives an unsightly 

blotchy appearance.

If finishes are applied following installation, brushing is 

the best method. If the finish is roller- or spray-applied, 

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, as this is the 

most important surface. Contact preservative treatment or 

fire-retardant manufacturer for their specific criteria for 

finishing.

Maintenance

As shakes and shingles age, they may become brittle. 

Walking on the roof can cause extensive cracking of 

aged shakes or shingles and may lead to leaks. 
General Technical Report FPL–GTR–201

10

We recommend that you hire a contractor having experience with maintaining wood roofs. The following 

information is given mainly so that you can be better 

informed when discussing your roof maintenance and 

refinishing with your contractor. The contractor will likely 

have proper ladders, scaffolds, safety equipment, and 

footwear and should know where to walk to minimize 

damage. Walking on the butt-end (lower edge of the shake 

or shingle) causes cracking. Cracking can be minimized by 

stepping on the upper part of the shake or shingle directly 

against the butt-end of the row above. 

Cleaning

Keep a clean roof. Eliminate the causes of debris 

accumulation and mold and moss growth. Remove all 

overhanging branches and if necessary, trees that encroach 

on the roof. If moss is growing on the roof or if leaves and 

other debris collect on the roof, they trap moisture and encourage decay, thereby decreasing the life expectancy of the 

roof. The use of zinc or copper strips mentioned previously 

can greatly decrease the growth of moss, algae, and mold, 

thus decreasing the need for cleaning.

A discolored roof caused by weathering and the growth 

of algae and molds can be cleaned quite effectively with 

chlorine bleach (5% sodium/calcium hypochlorite) or 

oxygen bleach (sodium percarbonate) mixed with water. 

We recommend commercial cleaners having sodium percarbonate as the active ingredient. Oxygen or chlorine bleach 

solutions quickly kill surface molds and algae. As the mildew is removed, the wood normally changes color from a 

dirty gray to buff tan. Over time, the ultraviolet radiation in 

sunlight will partially degrade wood surfaces. The bleach 

solution will remove some of the weathered wood fibers 

from the surface. It is best to use the weakest strength of 

cleaner possible and to apply it using a sprayer, sponge, or 

soft bristle brush to avoid further damage to the partially 

degraded surface. Strong cleaning solutions will remove 

excessive amounts of fiber from the surface. If you choose 

to use household bleach, begin with a mixture of one part 

bleach, five parts water, and a small amount of powdered 

detergent. 

Note: Do not use liquid detergents because they may 

react with bleach to form toxic fumes. After about 15 minutes, rinse thoroughly using a garden hose; keep the water 

stream pointed down the roof to avoid forcing water behind 

the courses of shakes or shingles. If this concentration 

doesn’t remove the mildew, then increase the concentration 

of bleach. It should not be necessary to use more than one 

part bleach and three parts water concentration. If the bleach 

solution is not effective, it is because residual finish in the 

surface of the wood is keeping the solution from absorbing 

into the wood.

Except in rare cases where there is an extensive build-up 

of moss growth and debris accumulation, it should not be 

necessary to power-wash wood roofs. Aggressive powerwashing in combination with strong cleaning solutions can 

damage wood roofs, particularly those made of cedar and 

redwood. If it is necessary to power-wash shake or shingle 

roofs, hire professionals having experience cleaning wood 

roofs, because in the wrong hands, power washers can easily remove an excessive amount of wood fiber. Loss of fiber 

drastically decreases the life expectancy of the roof. Contact 

preservative treatment or fire-retardant manufacturer for 

their specific criteria for cleaning.

Power Washing

In the rare case that power-washing of shakes 

and shingles is necessary, it should be done only 

by contractors having experience cleaning cedar. 

Keep the water stream pointed down the roof to 

avoid forcing water behind the courses of shakes or 

shingles. 

Refinishing

After the wood has dried (normally 2–4 days), reapply the 

WRP or oil-based semitransparent stain. A roof previously 

finished with a WRP can be refinished with a semitransparent stain. Follow the manufacturer’s recommendations for 

application, which usually includes recommendations for 

the 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 hours following 

application should be above 40–50° F (5–10° C), depending 

on the manufacturer. Minimum temperature is usually given 

on the label along with other application instructions and 

additional information is available from the company “help 

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

Other Sources of Information

Cedar Shake and Shingle Bureau

P.O. Box 1178

Sumas, WA 98295-1178

604-820-7700

www.cedarbureau.org

U.S. Forest Service

Forest Products Laboratory

One Gifford Pinchot Dr.

Madison, WI 53705-2398

608-231-9200

www.fpl.fs.fed.us

Copper Development Association

P.O. Box 144

Pocopson, PA 19366-0144

610-793-3868

www.copper.org
Installation, Care, and Maintenance of Wood Shake and Shingle Roofs

11

Maze Nails

100 Church St.

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