How To Install Cedar Shakes: A Professional Installation Guide
Installing cedar shakes requires a precise multi-layer approach involving consistent exposure measurements, proper ventilation, and strategic staggering of joints to ensure long-term moisture shedding and structural integrity. Adhering to the Cedar Shake and Shingle Bureau (CSSB) standards, including the use of corrosion-resistant fasteners and proper starter course offsets, is essential for maximizing the lifespan of the roof assembly.
Essential Preparation and Technical Requirements
Before breaking ground on a cedar shake installation, it is critical to confirm the structural soundness of the roof deck and the compatibility of the ventilation system. Cedar requires a breathing environment; trapped moisture leads to premature decay, rot, and cupping. Projects should be estimated based on the total surface area plus a 10% waste factor for complex hip or valley configurations.
- Essential Tools and Materials:
- Fasteners: Stainless steel ring-shank nails (Type 304 or 316) are mandatory to prevent galvanic corrosion and premature shake failure.
- Cutting Gear: Professional-grade circular saw with a fine-tooth blade, a sharp hatchet for hand-trimming, and a heavy-duty utility knife.
- Underlayment: High-quality breather-type felt or a specialized synthetic underlayment designed for wood shakes to facilitate moisture vapor transfer.
- Safety Equipment: Full body harness, dynamic rope lines, roof jacks, and slip-resistant footwear rated for steep-slope work.
- Material Specs: Premium grade, edge-grain, taper-sawn cedar shakes certified by the CSSB.
The Professional Cedar Shake Installation Workflow
Step 1: Substrate Preparation and Drip Edge Installation
Begin by verifying the roof deck is clean, dry, and free of protruding nails or debris. Install a corrosion-resistant metal drip edge along the entire perimeter. Apply the breather underlayment in horizontal courses, starting from the eaves and working toward the ridge. Overlap each course by a minimum of 4 inches to ensure water shed. If the pitch is below 4:12, additional waterproofing membranes may be required to prevent ice damming.
Step 2: The Starter Course Execution
The starter course is the most critical phase for ensuring a straight, uniform appearance. Install a double layer of shakes at the eave line to provide the necessary thickness and to conceal the joints of the first visible row. Ensure the starter shakes overhang the drip edge by approximately 1 to 1.5 inches.
Warning: Never align the joints of the starter course with the joints of the first visible course. Maintain a minimum lateral offset of 1.5 inches between joints of adjacent rows to prevent water penetration to the underlayment.
Step 3: Measuring and Managing Exposure
The exposure is the portion of the shake visible after installation. For standard 18-inch shakes, the maximum exposure is typically 7.5 inches, while 24-inch shakes allow for up to 10 inches. Use a chalk line to mark horizontal rows (courses) across the roof surface to maintain perfect alignment. As you move up the roof, periodically check your vertical progress against these lines to ensure you do not "drift" due to minor inconsistencies in shake width.
Step 4: Fastening and Joint Staggering
Place two nails per shake, positioned approximately 1 inch from each edge and 1.5 to 2 inches above the exposure line of the course above it. Drive nails until the head is flush with the wood surface; over-driving will crack the wood, while under-driving leaves a bump that compromises the seal of the course above.
Pro-Tip: Always maintain at least a 1/4-inch to 3/8-inch gap between individual shakes. This allows for natural expansion and contraction due to humidity changes, which prevents the shingles from buckling or splitting over time.
Step 5: Finishing the Ridge and Hips
Install pre-manufactured cedar ridge caps or site-cut shingles for the finish. These must be applied over a ridge vent system to maintain the continuous airflow required for the entire attic assembly. Secure the ridge caps with longer stainless steel nails, ensuring the fastener length is sufficient to penetrate through the ridge cap and into the roof sheathing.
Progress Report: A Peek At Our Cedar Shingle Siding (So Far) & How We ...
Cedar Shake Performance and Technical Specifications
| Feature | Specification | Impact on Longevity |
|---|---|---|
| Nail Type | Stainless Steel (304/316) | Prevents rust staining and fastener failure |
| Exposure | 7.5" (18" shakes) / 10" (24" shakes) | Ensures proper secondary moisture shedding |
| Gap Width | 0.25" to 0.375" | Prevents buckling during wet cycles |
| Underlayment | Breather-type / Synthetic | Prevents fungal growth on the underside |
Common Installation Errors and Field Remedies
- Root Cause: Insufficient joint staggering (joints aligning vertically).
- Actionable Fix: If observed during install, remove affected shakes and re-lay with a minimum 1.5-inch offset. If discovered post-completion, install shims or localized flashing patches behind the alignment.
- Root Cause: Over-driven nails causing stress fractures.
- Actionable Fix: Carefully pry up the head of the shake using a shingle ripper, apply a dab of exterior-grade wood sealant to the crack, and install a thin sheet metal flashing underneath the fracture point.
- Root Cause: Inadequate spacing (butting shakes tight together).
- Actionable Fix: If the roof is already buckling, individual shakes may need to be trimmed using a specialized hand saw or oscillating tool to re-establish the expansion gap, followed by a treatment with a wood preservative.
Frequently Asked Questions
Do I need to treat cedar shakes after installation?
While cedar is naturally decay-resistant, applying a wood preservative or fire retardant can significantly extend its service life. Consult the shake manufacturer’s warranty documentation before applying any chemical treatments to ensure compatibility.
Can I install cedar shakes over existing asphalt shingles?
This is generally discouraged because it traps moisture and adds excessive weight to the roof structure. It is standard practice to strip the old roof to the deck to inspect for rot and ensure proper installation of the underlayment and ventilation systems.
What is the ideal roof pitch for cedar shakes?
Cedar shakes perform best on roofs with a minimum pitch of 4:12. On lower slopes, the water shedding capability is reduced, necessitating high-performance secondary water barriers and strict adherence to exposure limits.
Why are stainless steel fasteners required?
Cedar contains natural tannins that are acidic and highly corrosive to standard galvanized steel. Using non-stainless fasteners will lead to premature "nail rot," causing the shakes to slide off the roof long before the wood itself has failed.
Elevate your roofing project by utilizing high-grade cedar shakes and professional-grade stainless hardware to ensure a durable, aesthetic finish. Contact a licensed roofing specialist or your local supplier to verify your material specifications and order the appropriate underlayment for your regional climate.
