How To Apply Cedar Shake Siding: A Technical Guide To Professional Installation

Achieving a durable and weather-tight cedar shake installation requires a dual-layered moisture management system, including a high-performance weather-resistive barrier and a dedicated rainscreen air gap. Precise execution hinges on maintaining a minimum 1.5-inch side lap between joints in successive courses and utilizing stainless steel fasteners to prevent tannin-reactive corrosion and wood splitting.

Strategic Planning and Material Logistics for Cedar Installation

The longevity of cedar shake siding is dictated more by the hidden layers behind the wood than the wood itself. Before the first shake is nailed, the building envelope must be prepared to handle vapor diffusion and liquid water ingress. Cedar is a hygroscopic material, meaning it expands and contracts significantly with moisture cycles. Failure to account for this movement leads to cupping, splitting, and premature finish failure.

Essential Gear and Tool Inventory

• Precision Hand Tools: Shingle hatchet (for trimming and gauging exposure), chalk line (blue or white only; red can stain), tape measure, and a block plane for fine-tuning mitered corners.
• Power Equipment: Sliding compound miter saw with a fine-tooth carbide blade, pneumatic siding nailer (coil-fed), and an air compressor regulated to 80-90 PSI.
• Safety Equipment: Level 3 cut-resistant gloves, ANSI Z87.1-rated eye protection, and fall protection gear if working above six feet.

Mandatory Material Specifications

• Cedar Shakes: Ensure shakes are CSSB-graded (Cedar Shake & Shingle Bureau). Premium "No. 1 Grade" shakes are recommended for wall applications to minimize flat-grain defects.
• Fasteners: Use only Type 304 or Type 316 stainless steel nails. Hot-dipped galvanized nails are acceptable in inland environments but will eventually react with cedar's natural tannins, causing black vertical streaks.
• Membranes: 30lb organic felt or a non-perforated synthetic house wrap. A 3/8-inch (10mm) drainage mat or furring strips are required to create a rainscreen.
• Flashing: Pre-bent stainless steel or heavy-gauge aluminum head flashings for windows and doors.

Project Benchmarks

• Estimated Duration: 12 to 16 man-hours per "square" (100 square feet) for complex walls with windows; 8 hours for simple gables.
• Budgetary Note: Cedar shake siding currently carries a material premium 3x higher than vinyl and 1.5x higher than fiber cement; however, it offers a 50-year service life when maintained.

Phase-by-Phase Technical Execution of Cedar Shake Siding

Step 1: Substrate Preparation and the Rainscreen Assembly

The wall must be structurally sound and sheathed with a minimum of 7/16-inch OSB or 1/2-inch plywood. Begin by installing the weather-resistive barrier (WRB), overlapping horizontal seams by 6 inches and vertical seams by 12 inches.

Install a rainscreen system over the WRB. This is typically achieved using vertical 1x3 furring strips aligned with the studs or a 3-dimensional plastic drainage matrix. This air gap allows the back of the cedar shakes to dry at the same rate as the front, preventing the "cupping" effect caused by differential moisture content. Install a bug screen or starter vent at the bottom of the rainscreen to prevent insect infestation while maintaining airflow.

Warning: Never install cedar shakes directly against a synthetic house wrap without a rainscreen. The surfactants in the wood can degrade the WRB’s water-repellency, leading to catastrophic sheathing rot.

Step 2: Establishing the Starter Course

The starter course provides the foundation and the necessary water-shedding overlap for the first visible course.

1. Snap a level chalk line around the perimeter of the building at the desired bottom edge height, usually 1 inch below the top of the foundation wall to protect the sill plate.
2. Install the first layer of the starter course, leaving a 1/8-inch to 1/4-inch gap between shakes to allow for expansion.
3. Apply a second layer of shakes directly over the first, ensuring that the vertical joints of the top layer are offset from the joints of the bottom layer by at least 1.5 inches.
4. Extend the bottom edge of the starter course 1 inch below the edge of the starter strip or sheathing to create a drip edge.

Step 3: Determining Exposure and Snapping Layout Lines

Exposure is the vertical portion of the shake that remains visible after the next course is applied. For 18-inch shakes, the maximum recommended exposure is 7.5 inches for walls. For 24-inch shakes, it is 10 inches.

1. Calculate the total height of the wall in inches.
2. Divide the height by the maximum allowed exposure to determine the number of courses.
3. Adjust the exposure slightly (usually by 1/8 or 1/4 inch) so that the courses align perfectly with the tops of window casings and door headers. This prevents the need for thin, unsightly "sliver" courses at the top of the wall.
4. Snap a chalk line for the top of each course across the entire work surface to ensure perfectly horizontal alignment.

Step 4: Fastening and Joint Management

Proper fastening is the most critical aspect of the installation. Each shake requires exactly two fasteners.

1. Drive nails approximately 3/4-inch to 1-inch from each side edge.
2. Position nails 1.5 to 2 inches above the "exposure line" (the part that will be covered by the next course).
3. Ensure nail heads are driven flush with the wood surface. Under-driving causes the next course to sit unevenly; over-driving crushes the wood fibers and creates a point for moisture collection.
4. Maintain a "side lap" of at least 1.5 inches. This means no joint in Course 3 should align vertically with a joint in Course 2.

Pro-Tip: If a shake is wider than 8 inches, it should be split into two narrower pieces or fastened with more nails to prevent the wood from cracking as it shrinks.

Step 5: Handling Corners and Trim Transitions

Corners can be finished using corner boards or mitered joints. For a traditional look, mitered corners are superior but require more labor.

• Corner Boards: Install 5/4-thick cedar trim boards at the corners first. Butt the shakes against the trim, leaving a 1/8-inch gap. Seal this gap with a high-quality color-matched sealant.
• Mitered Corners: Cut the ends of the shakes at a 45-degree angle. Alternate the overlap of the miter at each course to create a "woven" effect that enhances structural integrity and aesthetics.
• Window/Door Flashing: Ensure head flashings extend 2 inches beyond the sides of the casing and are tucked behind the WRB above them.

Dimensional Standards and Exposure Requirements

The following table outlines the maximum allowable exposure and fastener requirements based on the shake size and application type, following CSSB standards.

Common Installation Pitfalls and Field-Proven Remedies

Tannin Bleeding and Black Streaking

• Root Cause: The use of electro-galvanized or low-quality fasteners that react with the acidic extractives in Western Red Cedar.
• Actionable Fix: Clean the streaks using a solution of oxalic acid and water. Once dry, countersink the offending nails and cover the heads with a wood-tone exterior-grade putty, or replace the fasteners with stainless steel alternatives.

Significant Cupping or "Fish-mouthing"

• Root Cause: Installing shakes too tightly together without an expansion gap or failing to provide a rainscreen, causing the back of the shake to remain damp while the front dries.
• Actionable Fix: Individual cupped shakes must be removed by cutting the nails with a hack-saw blade. Replace the shake, ensuring a 1/4-inch gap from its neighbors, and use "face-nailing" with small-head stainless steel trim nails only if necessary to pull the board flat.

Vertical Joint Alignment (Zippers)

• Root Cause: Failing to maintain the 1.5-inch side lap across three consecutive courses, creating a direct path for water to reach the substrate.
• Actionable Fix: During installation, use a "story pole" or a gauge to verify that no joint in the current course is within 1.5 inches of a joint in the course immediately below it or the course two levels below it.

Frequently Asked Questions

Do cedar shakes require a felt interlay between courses?

For hand-split and resawn shakes, an 18-inch wide strip of 30lb felt should be interlaid between courses. The felt should be placed at a height twice the exposure measurement above the butt of the shake to ensure water is directed back to the weather surface. Sawn shingles do not require this interlay on walls but benefit from it on roofs.

Should I stain the shakes before or after installation?

Factory-priming or staining all six sides of the shake before installation is the gold standard. This "pre-dipping" ensures the back and edges are protected from moisture, significantly reducing the likelihood of cupping and tannin bleed. If staining on-site, apply the finish as soon as the moisture content of the wood is below 15%.

How do I calculate how much cedar shake siding to order?

Measure the total square footage of the walls and subtract the area of large openings like garage doors. Divide by 100 to get the number of "squares." Add a 10% waste factor for standard walls and a 15% waste factor for walls with complex gables or numerous windows.

Can I install cedar shakes over existing siding?

No. Cedar shakes require a flat, stable substrate and a functioning building envelope. Installing over old siding prevents the creation of a proper rainscreen and makes flashing transitions at windows and doors nearly impossible to seal correctly, leading to rot.

Elevate Your Home’s Building Envelope

Mastering the art of cedar shake application ensures your property remains protected from the elements while gaining the timeless aesthetic of natural wood. For high-performance results, always pair your premium cedar with stainless steel fasteners and a robust drainage system.