TL;DR:
When installing cedar roof caps in Canada especially in weather-challenged areas like Toronto, Hamilton, and the Niagara Region—it’s essential to choose the right underlayment to protect your roof from water damage, ice dams, and premature deterioration. Whether you’re using natural cedar or synthetic cedar shakes, the best installation includes an ice and water shield beneath the cap, followed by either 30 lb felt or a synthetic underlayment. Adding a cedar breather ensures ventilation and longer lifespan. This guide explains the ideal setup based on Canadian climate and material type.
Cedar roofs are admired for their rustic beauty and durability, but to perform in Canada’s freeze-thaw cycles and heavy snow loads, they need proper installation—especially at the vulnerable roof caps. Whether you’re installing natural cedar shakes or synthetic cedar alternatives (like Enviroshake® or Brava®), the underlayment system beneath the cap plays a critical role in roof performance and longevity.
Here’s what you need to know when working with both cedar types in Toronto, GTA, Hamilton, and Niagara.
Natural Cedar vs Synthetic Cedar: Key Differences
| Feature | Natural Cedar | Synthetic Cedar |
|---|---|---|
| Material | Western Red Cedar or Eastern White | Composite (rubber, plastic, polymer, recycled materials) |
| Appearance | Authentic wood grain, ages to silver-gray | Imitates real cedar, color-stable |
| Lifespan | 20–30 years (with maintenance) | 30–50+ years |
| Maintenance | High (needs cleaning, treatment, ventilation) | Low (resistant to rot, insects, mildew) |
| Weight | Lightweight | Heavier than natural cedar |
| Cost | Generally lower initial cost | Higher upfront investment |
| Installation | Requires breathability and drainage | Often installed over solid decking |
🧰 Bottom line: Natural cedar needs breathability (cedar breather + felt or synthetic underlay). Synthetic cedar benefits from stable, moisture-blocking underlayments like full synthetic sheets or ice & water shield.
Recommended Underlayment Setup
1. Ice and Water Shield
Use With: Both natural and synthetic cedar
Purpose: Self-sealing barrier for ridges, caps, eaves, and valleys
Why It’s Essential in Canada: Protects against:
- Ice dams
- Nail penetration leaks
- Wind-driven rain
🟩 Recommended Brands:
- Grace Ice & Water Shield®
- IKO ArmourGard™
- Resisto RedZone®
2. 30 lb Asphalt Felt (Traditional Underlayment)
Use With: Natural cedar
Pros: Budget-friendly, proven performance
Cons: Absorbs water, degrades over time, not breathable
Installation Tip: Always use with a cedar breather or vent mat to allow airflow beneath cedar.
3. Synthetic Underlayment
Use With: Both cedar types, especially synthetic
Pros: UV-resistant, tear-resistant, highly durable
Cons: More expensive
Best For: Roofs with steep pitch or long exposure times before shingle installation
🟩 Popular in Canada:
- Titanium® UDL
- Resisto® Synthetic
- Grace Tri-Flex®
4. Cedar Breather or Ventilation Mat
Use With: Natural cedar only
Purpose: Provides essential air gap between wood and underlayment
Prevents: Mold, mildew, premature rot
🟩 Popular Options:
- Benjamin Obdyke Cedar Breather®
- VentGrid®
Ideal Layered Assembly for Cedar Roof Caps
| Layer | Natural Cedar Cap | Synthetic Cedar Cap |
|---|---|---|
| Cap Shingles | Cedar shakes | Synthetic cedar shakes |
| Ventilation Mat | ✅ Required | ❌ Optional |
| Underlayment | 30 lb Felt or Synthetic | Synthetic (preferred) |
| Ice & Water Shield | ✅ Always | ✅ Always |
Why This Matters in Canadian Climate
- Natural cedar expands and contracts with moisture. Without ventilation, it warps and decays fast.
- Synthetic cedar is more stable, but still benefits from ice and water protection to prevent moisture buildup and rot at fastener points.
- All roofs in Ontario are subject to extreme cold, snow loads, and sudden thaws—making water protection a non-negotiable.
Final Thoughts
If you’re installing natural cedar, your priority is ventilation and moisture escape — so felt + cedar breather + ice shield is a proven trio. For synthetic cedar, moisture resistance and stability matter more — go with full synthetic underlayments and ice & water shield for leak protection.
Cedar roofs look amazing — make sure they last as long as they should with proper underlayment planning.
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📞 Need Help With Cedar Roof Installation or Soft Washing?
The Cedar Cleaners are your local specialists in Toronto, GTA, Hamilton, and Niagara.
Call 647-694-0523 or visit thecedarcleaners.ca to book a quote or inspection.