When Fort Wayne homeowners think about their roof, they think about shingles. But beneath those shingles is a layer most people never see: the underlayment. And in many ways, this invisible barrier is more important to your home’s protection than the shingles on top of it.

Underlayment is the waterproof or water-resistant sheet material installed directly on the roof deck before shingles are applied. It serves as your roof’s secondary defense — the backup system that keeps water out when shingles are compromised by wind, hail, ice, or age.

What Underlayment Actually Does

Shingles shed water through gravity and overlap. But wind-driven rain pushes water sideways under shingle edges. Hail cracks shingles. Ice dams pool water. When water gets past the shingle layer, underlayment is the difference between “water drained harmlessly” and “water soaked through to the roof deck and dripped into my living room.”

Types of Roof Underlayment

Asphalt-Saturated Felt (Tar Paper)

Traditional felt underlayment has been used for over a century. It absorbs water when exposed for extended periods, tears more easily during installation, and can become brittle in Indiana’s temperature swings. While still code-compliant and the cheapest option, most reputable Fort Wayne roofers have moved to synthetic.

Synthetic Underlayment

Made from engineered polypropylene or polyethylene — inherently waterproof rather than water-resistant. Stronger, lighter, and more durable than felt. Doesn’t absorb water or wrinkle. Lies flatter on the deck. Resists tearing and UV exposure. The cost difference is typically $200 to $500 for a complete Fort Wayne home — well worth it for dramatically better performance over 25+ years.

Ice and Water Shield (Self-Adhering Membrane)

A premium, self-adhering membrane that creates a completely watertight seal. Unlike other underlayments, it sticks directly to the plywood, sealing around nail penetrations. Used at the most vulnerable areas: along eaves where ice dams form, in roof valleys, around chimneys, skylights, and penetrations, and along wall-to-roof transitions.

The self-sealing property is unique — when a nail is driven through it, the material closes around the nail shaft, preventing water from following it down.

Indiana Building Code Requirements

Indiana code requires at least one layer of approved underlayment over the entire roof deck, and ice and water shield along the eaves extending at least 24 inches past the interior wall line.

At Big Dog Roofing, we exceed code minimum for ice and water shield — typically installing it 3 to 6 feet from the eave edge, plus in all valleys and around every penetration. In Fort Wayne’s climate, those extra feet of protection pay for themselves the first time ice builds along your roofline.

How Bad Underlayment Leads to Premature Roof Failure

Cheap or improperly installed underlayment is one of the leading causes of premature roof failure — and it’s completely invisible once shingles are on. Wrinkled felt creates channels where water flows sideways. Improperly overlapped seams let water reach the deck. Missing ice and water shield leaves the most vulnerable area unprotected.

Questions to Ask Your Roofer About Underlayment

When getting estimates for a roof replacement, ask: What type of underlayment do you use? How far do you extend ice and water shield from the eave? Do you install it in valleys and around all penetrations? Is it included in the quote? What specific brand and product?

A contractor who can’t answer these questions clearly is cutting corners in the one area you’ll never be able to inspect after installation.

Big Dog Roofing: Quality Below the Surface

Every roof we install uses premium synthetic underlayment across the full deck and ice and water shield at all vulnerable areas. We document the underlayment installation with photos so you have proof of what’s protecting your home beneath the shingles.

Want to know what’s under your shingles? Schedule a free roof inspection. Call 260-999-0347 or request your inspection online.