Synthetic vs. Felt vs. Peel-and-Stick Underlayment: What Belongs Under Your Roof
The waterproof layer under your shingles matters more than the shingles themselves. Synthetic, felt, and peel-and-stick compared for 2026 installs.
The shingles get all the marketing. The underlayment does the actual waterproofing. Most 2026 leaks trace back to underlayment shortcuts, not shingle failure.
15-lb and 30-lb felt (asphalt-saturated paper)
The old standard. Cheap ($15–$25 per square). Tears easily during install and degrades in UV within days.
Still allowed by most codes but rarely used on quality installs in 2026.
Synthetic underlayment
Woven polypropylene, 4–6x stronger than felt, UV-stable for 90–180 days. $35–$60 per square.
Should be your default field underlayment. GAF Deck-Armor, Owens Corning ProArmor, Titanium UDL 50 are all appropriate.
Peel-and-stick (self-adhering) — ice and water shield
Rubberized asphalt with a peel-off backer. Seals around every nail penetration. $80–$140 per square.
Code-required in the first 24" past the wall line in cold-climate zones (IRC R905.1.2). Best practice: also use in valleys, around penetrations, and full deck coverage on low-slope sections.
What a proper 2026 stack looks like
Ice-and-water shield along eaves, valleys, and penetrations. Synthetic across the rest of the field. Never mix felt and synthetic on the same slope.
Frequently Asked Questions
- Can I upgrade to full peel-and-stick coverage?
- Yes, and in hurricane, hail, and heavy-snow markets it's often the best $2,500–$4,000 you'll spend. Some manufacturers extend warranty for full peel-and-stick decks.
- Does synthetic void my shingle warranty?
- No — as long as it's a compatible product from the same or approved brand. Check the shingle warranty document's 'accessory products' list.
Choosing materials for your roof?
Compare brands and price your project before you sign anything.