How To Install Cedar Shakes: A Professional Technical Guide

Master the precise installation techniques required for long-lasting, weather-tight cedar shake roofs and sidewalls in accordance with Cedar Shake & Shingle Bureau (CSSB) standards and IRC R905.8 building codes. Proper execution demands careful material selection, continuous 18-inch felt interlaying, exact keyway spacing between 3/8" and 5/8", and strict fastener placement to prevent premature cupping, splitting, and water intrusion.

Pre-Installation Planning, Underlayment Specs, and Tool Requirements

A successful cedar shake installation requires accurate slope calculations, structural deck assessment, and appropriate moisture management systems. Cedar shakes are heavy, split-wood materials that absorb and release atmospheric moisture; therefore, the roofing assembly must accommodate thermal movement while providing complete weatherproofing. Prior to beginning, ensure the roof deck consists of either minimum 15/32-inch exterior-grade plywood, 7/16-inch Oriented Strand Board (OSB), or 1x6 space-sheathing boards designed specifically for un-creosoted cedar shake ventilation.

Essential Materials, Tools, and Prerequisites Checklist

• Cedar Shake Stock: Grade 1 Hand-Split Resawn or Taper-Sawn Cedar Shakes (18-inch or 24-inch lengths).
• Fasteners: 304 or 316 Stainless Steel, or Hot-Dipped Galvanized (ASTM A153 Class D) ring-shank box nails (minimum 5d or 6d depending on shake thickness). Stainless steel is mandatory in coastal environments within 15 miles of saltwater.
• Underlayment: Type 30 (30 lb) un-perforated organic asphalt-saturated felt meeting ASTM D226 Type II specifications, along with self-adhering modified bitumen ice and water shield for valleys and eaves.
• Flashing Components: Minimum 26-gauge corrosion-resistant sheet metal (copper, lead-coated copper, painted aluminum, or stainless steel) for step flashing, valleys, drip edges, and wall terminations.
• Specialized Tools: Roofing hatchet with adjustable gauge, pneumatic coil nailer (with flush-drive nose cone), chalk line, spring-loaded utility knife, tin snips, hand hammer, and safety harness system meeting OSHA standards.
• Labor & Schedule Benchmarks: Expect a baseline production rate of 1.5 to 2.5 roof squares (150-250 sq ft) per installer per 8-hour shift. Budget approximately 3 to 4 working days for a standard 20-square residential installation with a two-person crew.

Step-by-Step Cedar Shake Installation Execution

Step 1: Deck Inspection and Eave Sub-Structure Preparation

Verify that the underlying roof deck is structurally sound, clean, dry, and free of protruding fasteners. The roof pitch must measure at or above 4:12 (approx. 18.4 degrees); slopes lower than 4:12 require special waterproofing membranes or alternate roofing systems entirely. Install a corrosion-resistant drip edge flashing along the eave lines, overlapping joints by a minimum of 2 inches.

In cold-climate zones subject to ice damming, apply a self-adhering polymer-modified bitumen membrane directly over the deck sheathing. Extend this ice barrier from the lowest eave edge to a point at least 24 inches inward past the interior warm-wall line.

Warning: Do not substitute synthetic breathable underlayments for 30 lb organic asphalt felt when installing hand-split cedar shakes. Natural wood extractives (tannins) leach out when wet and can break down the surface tension coatings of synthetic membranes, causing premature system leaks.

Step 2: Laying the Double-Layer Starter Course

The base course of the roof requires a double layer of cedar shakes (or a cedar shingle starter layer beneath a shake layer) to provide structural strength and weatherproofing at the eave overhang.

1. Install a 36-inch wide strip of ASTM D226 Type II 30 lb asphalt felt directly over the eave drip edge.
2. Align the first layer (the undertown starter course) so that it overhangs the eave drip edge by 1-1/2 inches and the rake edges by 1 inch. Secure each shake using two fasteners placed 3/4 inch inward from the lateral edges and 1-1/2 inches above the butt line.
3. Lay the primary outer starter course directly over the undertown course. Offset all vertical joints (keyways) between the top layer and the bottom layer by a minimum of 1-1/2 inches to prevent water from tracking through aligned seams.
4. Maintain a lateral expansion gap of 3/8 inch to 5/8 inch between adjacent shakes in the starter course.

Pro-Tip: Cedar expands significantly when wet. Failing to leave a minimum 3/8-inch gap between shakes will cause the wood to buckle, ridge, or split as it absorbs rainwater.

Step 3: Establishing Exposure Lines and Applying Interlaying Felt

Unlike cedar shingles—which rely on continuous underlayment—cedar shakes require an interlaying felt paper strip between every single course. This interlaid felt acts as a baffle system, preventing wind-driven snow and rain from infiltrating the exposed joint gaps.

[ Course 3 Shake ] | | === Interlay Felt Strip (18") === | | [ Course 2 Shake ] | | === Interlay Felt Strip (18") === | | [ Starter Course ]

1. Determine the maximum weather exposure based on shake length and roof pitch. For standard 18-inch resawn shakes on slopes 4:12 and steeper, the maximum exposure is 7-1/2 inches. For 24-inch shakes, the maximum exposure is 10 inches.
2. Snap a blue chalk line across the roof at the designated exposure height measured up from the butt line of the starter course.
3. Position an 18-inch-wide strip of Type 30 asphalt felt such that its bottom edge sits above the butt line of the course being applied at a distance equal to twice the exposure length. For example, with a 10-inch exposure on a 24-inch shake, place the lower edge of the felt 20 inches above the butt of the shake.
4. Fasten the felt high on the sheet using just enough staples or roofing nails to hold it flat against the deck sheathing. The top portion of the felt strip must extend up over the unexposed wood deck.

Step 4: Installing Subsequent Field Courses

Work across the roof deck from left to right (or right to left), maintaining consistent alignment along the chalked exposure line.

1. Position each shake so its butt edge aligns precisely with the chalk line.
2. Check the keyway offset: Ensure that the vertical joint between any two adjacent shakes is offset by at least 1-1/2 inches from the vertical joints in the course directly below it.
3. Ensure that no keyways in alternate courses align directly over one another within a 3-course span.
4. Fasten each individual shake using strictly two fasteners. Place nails or staples 3/4 inch to 1 inch in from each outer edge, and approximately 1 inch to 2 inches above the weather exposure line. Never drive fasteners into the exposed face of the shake.
5. Set the fastener heads flush with the wood surface. Do not countersink or crush the wood fibers, as this compromises the holding power and creates water traps.

Warning: Never use more than two fasteners per shake regardless of its width. Over-nailing restricts the natural expansion and contraction cycles of the wood, causing the shake to split down the center.

Step 5: Flashing Valleys, Sidewalls, and Chimney Intersections

1. Open Valleys: Construct open valleys using 26-gauge metal shaped into a continuous W-profile. Extend the valley metal at least 11 inches on either side of the center line (22 inches total width). Trim the cedar shakes back to leave a minimum 6-inch open water channel (3 inches on each side of the center rib at the top, widening out by 1/8 inch per linear foot downward). Cut shake ends at an angle to match the valley alignment; do not drive fasteners into the valley flashing within 5 inches of its centerline.
2. Step Flashing at Sidewalls: Integrate 26-gauge step flashing pieces (minimum 3" x 3" or 4" x 4" legs, 8 inches long) at every wall termination. Interlace one piece of step flashing with each shake course, placing the metal under the shake and running the vertical leg up behind the exterior wall cladding or counter-flashing.

Step 6: Installing Hip and Ridge Caps

Finish the roof peak and hip intersections using manufactured factory-assembled hip and ridge units or custom site-cut shakes using the alternating lap method.

1. Lay a 12-inch-wide strip of 30 lb asphalt felt along the peak or hip centerline before applying caps.
2. Select pre-assembled hip and ridge units or construct them by beveling the edge of one shake to butt flush against the face of its adjacent partner.
3. Alternate the overlap direction on every successive cap unit (e.g., left over right on course one, right over left on course two) to produce a uniform appearance and maximum weather protection.
4. Fasten caps using long, corrosion-resistant nails that penetrate through the underlying shake layers and deep into the roof deck sheathing by a minimum of 3/4 inch. Ensure exposure on hip and ridge caps matches the field shake exposure (e.g., 7.5 inches exposure for 18-inch caps).

Cedar Shake Installation Technical Specifications & Exposure Parameters

Common Site Failures and Field Remedies

Scenario 1: Shakes Cupping, Curling, and Ridging Across Field Courses

• Root Cause: The installer set the keyways (expansion gaps between adjacent shakes) too tight (less than 1/4 inch). When rain saturated the wood, normal lateral expansion forced the cedar upward off the deck surface.
• Actionable Fix: Identify cupped shakes. Using a reciprocating saw with a thin wood blade, run the blade vertically up through the tight keyway joints to slice off 1/4 inch of material on one side, releasing the physical compression tension. Replace severely cracked or fractured shakes entirely by pulling fasteners with a flat pry bar (shingle ripper), sliding in a new shake, and blind-nailing beneath the overlapping course.

Scenario 2: Severe Longitudinal Splitting Along Fastener Alignment

• Root Cause: Over-nailing (using 3 or 4 fasteners per shake) or driving nails too close to the outer lateral edges (less than 3/4 inch). Fasteners restrict structural wood movement as humidity levels change.
• Actionable Fix: Extract the split shake using a shingle ripper tool. Insert a replacement shake cut to size (ensuring a 3/8-inch to 5/8-inch clearance). Drive only two fasteners at the proper height (1 to 2 inches above the exposure line and 3/4 inch from the outer edge). If access prevents blind nailing, face-nail the new shake with stainless steel ring-shank nails fitted with neoprene sealing washers.

Scenario 3: Leak Intrusion During Wind-Driven Rain or Snow Melt

• Root Cause: Missing or improperly placed 18-inch interlaying felt strips, or failure to maintain the 1-1/2-inch minimum side-lap offset between keyways across adjacent courses.
• Actionable Fix: Locate the interior leak origin and trace it vertically up the slope. Carefully remove the offending shake courses using a shingle ripper. Slide replacement 18-inch strips of Type 30 asphalt felt behind the underlying course so that the lower felt edge sits at twice the exposure height above the butt line. Re-install shakes, strictly adhering to the 1-1/2-inch offset rule for all vertical joints.

Scenario 4: Black Staining or Bleeding Around Fastener Heads

• Root Cause: Use of standard electro-galvanized or electro-plated steel nails. Cedar contains high concentrations of natural tannic acids, which aggressively react with plain iron and low-grade zinc coatings, causing chemical corrosion and dark wood staining.
• Actionable Fix: Replace non-compliant fasteners. Carefully lift the overlapping shake butts to expose the nail heads. Remove corroded nails or cut them off using an oscillating multi-tool fitted with a carbide metal-cutting blade. Re-secure the shakes using 304 or 316 grade stainless steel ring-shank box nails. Clean iron tannin stains using an oxalic acid wood restoration wash applied per manufacturer directions.

Frequently Asked Questions

What is the primary difference between installing cedar shingles and cedar shakes?

Cedar shingles are sawn smooth on both sides and installed over continuous solid underlayment, whereas cedar shakes are rough-split (or taper-sawn thicker) and strictly require 18-inch wide strips of 30 lb asphalt felt interlaid between every individual course to prevent wind-driven moisture penetration through their uneven surfaces.

Can cedar shakes be installed over solid plywood decking?

Yes, cedar shakes can be installed over solid 15/32-inch plywood or 7/16-inch OSB deck panels, provided that continuous 18-inch Type 30 interlaying felt strips are properly installed with every course. In humid or wet climates, placing a 3D matrix rainscreen ventilation mat between the deck and the first shake layer significantly enhances drying potential and extends system life.

Why are pneumatic standard roofing nails unacceptable for cedar shake installation?

Standard smooth-shank electro-galvanized roofing nails lack the necessary corrosion resistance against cedar's natural tannic acids and do not possess adequate withdrawal resistance. Installers must use ring-shank box nails manufactured from 304/316 stainless steel or hot-dipped galvanized steel meeting ASTM A153 Class D standards to prevent nail decay and wind blow-offs.

What is the minimum slope requirement for installing a cedar shake roof?

The standard minimum slope for installing cedar shakes is 4:12 (4 inches of vertical rise per 12 inches of horizontal run). Installing cedar shakes on roof slopes below 4:12 is not recommended by the Cedar Shake & Shingle Bureau, as low slopes retard water runoff and lead to rapid moisture absorption, premature decay, and structural roof leaks.

How do you determine the correct fastener length for cedar shakes?

Fastener length must be sufficient to penetrate through the shake material and pass completely through the underside of the roof deck sheathing by at least 1/8 inch, or penetrate a minimum of 3/4 inch into solid wood plank sheathing. Typically, 18-inch medium shakes require 5d (1-3/4") box nails, while 24-inch heavy shakes require 6d (2") or 7d (2-1/4") box nails.

Professional Roofing System Verification

Executing a high-performance cedar shake installation requires strict adherence to architectural specifications, regional building codes, and proven regional craftsmanship. Ensure every square of shakes incorporates correct fasteners, rigorous 18-inch felt interlaying, and precise keyway alignment to guarantee decades of resilient protection.