Cedar Shake and Shingle Installation Guidelines and Best Practices

Cedar shake and shingle roofs offer a classic, durable, and aesthetically pleasing option for residential and commercial structures. However, their performance and longevity depend heavily on proper installation, material selection, and adherence to best practices. The Cedar Shake & Shingle Bureau (CSSB) provides detailed guidance to ensure these natural wood products meet high standards of quality and functionality. This article compiles key installation instructions, repair and maintenance practices, product types, and underlayment recommendations based on official CSSB resources and additional technical insights.

Understanding Cedar Shake and Shingle Types

Cedar shakes and shingles are distinct in their manufacturing processes, appearance, and installation requirements. The Cedar Shake & Shingle Bureau categorizes these materials into specific types, each with defined characteristics and uses.

Certi-Split® Handsplit and Resawn Shake

Certi-Split shakes are produced by splitting the face of the cedar log and then resawing the back to create a more uniform shape. These shakes are known for their rustic appearance and are commonly available in 18-inch and 24-inch lengths. The butt thickness of these shakes typically ranges from 3/8 inch to 1 inch, with jumbo resawn shakes having a minimum butt thickness of 1 inch. This type is ideal for traditional or rustic architectural styles.

Certigrade® Shingle

Certigrade shingles are sawn on both sides, providing a more uniform and refined appearance. They are available in three standard lengths: 16 inches (Fivex), 18 inches (Perfection), and 24 inches (Royal). The butt thickness is standardized using a stack of shingles to ensure consistency. These shingles are suited for contemporary or semi-traditional designs where a smoother texture is desired.

Certi-Sawn® Tapersawn Shake

Certi-Sawn tapersawn shakes are sawn on both sides, offering a semi-textured appearance with a more pronounced shadowline than shingles. This type is often used in applications where a balance between texture and uniformity is preferred. Common lengths include 18 inches and 24 inches, with butt thicknesses ranging from 5/8 inch to 1½ inches.

Each product type has specific installation and exposure requirements. The CSSB recommends consulting their full product catalog for detailed specifications and grading criteria.

Installation Best Practices

Proper installation is critical to the performance and longevity of cedar shake and shingle roofs. The CSSB outlines several best practices to ensure correct application and alignment. These guidelines are intended to be visible without destructive evaluation and cover spacing, course alignment, fastener use, and ventilation.

Spacing and Alignment

Uniform spacing is essential to both aesthetics and functionality. For shakes, the recommended gap between units is 3/8 inch to 5/8 inch. For shingles, the gap should be between 1/4 inch and 3/8 inch. Adjacent courses must be offset by a minimum of 1½ inches to prevent direct alignment. Shingles should not have more than 10% of joints aligned in alternate courses.

Even courses and consistent exposure lengths are also important. No shake or shingle should be overexposed, especially in a staggered butt application. The maximum allowable exposure length should not be exceeded to maintain the roof’s weather resistance and structural integrity.

Fastener and Interlayment Considerations

Exposed fasteners are a red flag in cedar shake and shingle installations. All fasteners should be covered or embedded in the wood to prevent corrosion and aesthetic issues. Shingles do not require interlaid felt, and using it is a violation of the International Residential Code (IRC) and International Building Code (IBC).

For shake installations, the CSSB recommends interlaying felt between shakes starting at two times the exposed length of the shake above the shake butt. This practice enhances weather resistance and reduces the risk of water infiltration.

Sheathing and Underlayment Options

Solid sheathing is preferred for shake installations and may be required in seismic zones or under treated shakes and shingles. The only solid sheet sheathing that has been tested with Certi-label shakes and shingles is plywood, though some manufacturers may allow the use of oriented strand board (OSB). Local building codes should be consulted for specific thickness, grade, and dimension requirements.

The recommended underlayment for cedar shakes is No. 30 ASTM D4869 Type IV or No. 30 ASTM D226 Type II. For shingles, a permeable underlayment is also recommended. Non-permeable underlayment should not cover the entire roof deck, especially in high-wind zones. Local building codes should be checked for underlayment attachment requirements.

Special Installation Considerations

Certain roof types, such as mansard and low-slope roofs, require specific installation techniques. The CSSB provides detailed guidance for these applications to ensure proper water management and structural integrity.

Mansard Roofs

Mansard roofs have a steep upper slope and a flatter lower slope. Installation on these roofs must account for the varying slope angles and potential water runoff patterns. Additional flashing and underlayment considerations are necessary to prevent water accumulation in the flatter sections.

Low-Slope Roofs

Low-slope roofs require careful attention to underlayment and drainage. The CSSB recommends a minimum slope of 1/4 inch per foot for cedar shakes and shingles. Proper ventilation and drainage systems are essential to prevent water pooling and prolong the roof’s lifespan.

Flashing and Valley Installation

Roof valleys are particularly vulnerable to water infiltration and require careful flashing. The CSSB provides recommended flashing materials and installation details for valleys to ensure effective water shedding. Flashing should extend beyond the valley and be sealed at intersections with other roof components.

For roof projections such as chimneys and vents, the CSSB provides detailed flashing guidelines. These materials and methods are designed to prevent water intrusion while maintaining the aesthetic integrity of the roof.

Repair and Maintenance Guidelines

Cedar shake and shingle roofs require periodic maintenance to extend their service life and maintain performance. The CSSB outlines several repair and maintenance considerations, including natural aging versus damage, replacement techniques, and disposal practices.

Natural Aging vs. Damage

The service life of a cedar roof is influenced by environmental conditions, wood quality, installation quality, and maintenance. Natural aging may include color fading and surface wear, while damage can result from improper installation, foot traffic, or exposure to overhanging trees. Regular inspections are recommended to identify and address issues early.

Individual Shake or Shingle Repair

Individual shakes or shingles can be replaced or repaired if damaged. The CSSB recommends blending new and old materials to maintain a consistent appearance. Replacement should be done carefully to avoid disturbing adjacent units.

Fastener Failure

Fastener failure is a common issue in cedar roofs, particularly in areas with high humidity or frequent temperature changes. Failed fasteners should be replaced promptly to prevent further damage.

Maintenance and Upkeep

Regular maintenance includes removing debris, trimming overhanging branches, and inspecting for signs of wear or water infiltration. Proper attic ventilation is also essential to prevent moisture buildup and prolong the roof’s life.

Disposal and Recyclability

Cedar shake and shingle materials are generally biodegradable and can be recycled or repurposed. The CSSB provides guidelines for the responsible disposal of these products, including options for reuse in landscaping or construction projects.

Conclusion

Cedar shake and shingle roofs offer a timeless, durable, and aesthetically pleasing option for a wide range of structures. However, their performance and longevity depend on proper installation, material selection, and ongoing maintenance. The Cedar Shake & Shingle Bureau provides comprehensive guidelines to ensure these natural wood products meet high standards of quality and functionality. By following best practices for spacing, alignment, fastening, underlayment, and special installation considerations, professionals and DIY enthusiasts can achieve a long-lasting, visually appealing cedar roof. Regular inspections and maintenance further contribute to the roof’s durability and weather resistance.