When most homeowners think of their roof, they picture shingles. But the real protection begins beneath the shingles — with your roof's underlayment.
At Nest Exteriors, we treat underlayment like what it is: your roof’s last line of defense against leaks, rot, and premature failure. And not all underlayments are created equal.
This guide explains the differences between felt, synthetic, and ice & water shield underlayments — so you can make an informed choice when it’s time to replace your roof.
What Is Roof Underlayment?
Underlayment is a water-resistant (or waterproof) barrier installed between the roof decking and your shingles. It protects the structure of your roof from moisture infiltration due to wind-driven rain, ice dams, and shingle blow-off.
It also provides a smooth surface for shingle installation and some additional insulation value.
1. Felt Underlayment (Also Called Tar Paper)
What It Is:
An asphalt-impregnated paper product used for decades as a basic moisture barrier.
Pros:
- Inexpensive
- Widely available
- Familiar to many contractors
Cons:
- Tears easily during installation or in high winds
- Breaks down faster over time
- Absorbs moisture rather than repelling it
Lifespan:
10–15 years (often less if exposed to high heat or improper installation)
Verdict:
Outdated. At Nest, we rarely recommend felt unless budget is the top priority — and even then, we walk clients through the long-term tradeoffs.
2. Synthetic Underlayment
What It Is:
Made of polypropylene or polyethylene, synthetic underlayment is designed to be more durable and moisture-resistant than felt.
Pros:
- Lightweight and easy to install
- Strong and tear-resistant
- Repels water rather than absorbing it
- More slip-resistant for installers (safer)
Cons:
- Slightly more expensive than felt
- Quality varies across brands (we use trusted names only)
Lifespan:
20–30 years, depending on manufacturer and climate
Verdict:
Our standard at Nest Exteriors. It balances performance, longevity, and affordability. Great for asphalt, metal, and synthetic shingle roofs.
3. Ice & Water Shield (Peel-and-Stick Membrane)
What It Is:
A self-adhering waterproof membrane installed in the most vulnerable areas of your roof: eaves, valleys, roof penetrations, and low-slope areas.
Pros:
- 100% waterproof, not just water-resistant
- Seals around nails to prevent leaks
- Critical for ice dam protection
Cons:
- More expensive per square foot
- Overkill for areas not prone to water buildup
Lifespan:
25+ years
Where We Use It:
- Along roof edges (eaves and rakes)
- In valleys
- Around chimneys, skylights, and vents
- On low-slope roof areas
Verdict:
Essential for protection against leaks and ice dams. While not used across the entire roof (unless specified), it is vital in key zones.
Why the Right Underlayment Matters
Think of underlayment as your roof's safety net. Shingles are your first layer of defense, but once they fail (due to wind, wear, or poor installation), underlayment is the only thing standing between your home and water damage.
Poor-quality underlayment can lead to:
- Mold and rot in decking
- Sagging ceilings
- Interior wall damage
- Costly repairs from insurance claim denials
How Nest Exteriors Builds It Better
- We use synthetic underlayment as our base standard for every project
- We install ice & water shield in all valleys, eaves, and penetrations (not just where code requires)
- We provide photos of all underlayment during your roof installation so you can see the protection in place
- We follow manufacturer specs to ensure your material warranty stays valid
Final Word: It’s What’s Underneath That Counts
A roof replacement is more than a visual upgrade — it’s a layered defense system. Choosing the right underlayment is a critical step in preventing leaks and preserving your home’s value.
Ready to inspect your current system or get a quote?
Let Nest Exteriors show you what true protection looks like.
Book Your Free Roof Inspection Today
