Roof Underlayment Types and Costs: Felt vs. Synthetic vs. Self-Adhering
Updated June 2026 · 13 min read
Underlayment is the layer your roofer installs directly on the wood deck before shingles go on — and it is the difference between a minor shingle problem and a soaked attic when weather hits. Most homeowners never think about it, but it is a line item in every roofing quote. Here is what each type does, what it costs, and when the upgrade to premium underlayment is worth it.
Roof Underlayment Cost Comparison — 2026
| Type | Cost / sq ft | 20-sq roof | Best for |
|---|---|---|---|
| 15-lb asphalt felt | $0.35–$0.55 | $700–$1,100 | Budget installs, mild climates |
| 30-lb asphalt felt | $0.45–$0.65 | $900–$1,300 | Better than 15-lb; still inferior to synthetic |
| Synthetic underlayment | $0.45–$0.85 | $900–$1,700 | Most new residential roofs |
| Ice-and-water shield (self-adhering) | $0.65–$1.05 | $1,300–$2,100 (full coverage) | Cold climates, eaves, valleys, penetrations |
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The three main underlayment types
Asphalt felt (15-lb and 30-lb)
$0.35–$0.65 / sq ft installedTraditional felt paper is saturated with asphalt to create a basic moisture barrier. 15-lb felt (also called #15 or Type I) is the thinnest and cheapest option. 30-lb (Type II) is heavier and more tear-resistant. Both are still widely used and meet minimum code requirements in most jurisdictions.
Advantages
+Lowest cost
+Widely available
+Accepted by most manufacturers as minimum warranty requirement
Limitations
−Tears easily when wet or walked on during installation
−Can wrinkle and buckle in heat
−Shorter exposed-installation window (24–48 hours before shingles needed) vs. synthetic
Synthetic underlayment
$0.45–$0.85 / sq ft installedSynthetic underlayment is made from woven or spun polypropylene or polyethylene. It has largely replaced felt on new residential roofs due to its superior performance characteristics. Most major roofing contractors now use synthetic as their standard.
Advantages
+4–6× stronger than felt; does not tear or wrinkle
+Can be left exposed for 30–90 days during multi-stage construction
+Lighter weight — easier and faster to install
+Slip-resistant surface; better footing for roofers
Limitations
−Higher cost than felt (though often only $100–$200 difference on a full roof)
−Slippery when wet on very steep pitches with some products
Self-adhering ice-and-water shield
$0.65–$1.05 / sq ft installedIce-and-water shield is a peel-and-stick membrane made from modified bitumen with a sticky adhesive backing. It bonds directly to the wood deck and creates a completely watertight seal — including around fasteners. It is required by code at eaves in cold climates (IRC code: minimum 24 inches inside the warm wall line) and is best practice at all valleys and penetrations everywhere.
Advantages
+Seals completely around nails — prevents water intrusion at fastener holes
+Protects against ice dam backup in cold climates
+Required by code in most northern states; strongly recommended in all climates at high-risk areas
Limitations
−Most expensive option
−Not necessary as full-roof coverage in warm climates — targeted application is cost-effective
Where ice-and-water shield is required (and recommended)
| Location on roof | Cold climates (zone 5–8) | Warm climates (zone 1–4) |
|---|---|---|
| Eaves (first 3–6 ft from edge) | Required by IRC code | Best practice; not required |
| All valleys | Required | Strongly recommended |
| Around chimneys | Recommended | Recommended |
| Around skylights | Recommended | Recommended |
| Roof-to-wall transitions | Recommended | Recommended |
| Full roof coverage | High-risk zones only | Not necessary |
How ice dams form — and why underlayment is the fix
Ice dams are the most common cause of winter roof leaks in northern states — and they are fundamentally an underlayment problem, not a shingle problem. Understanding the mechanism explains why self-adhering ice-and-water shield is not optional in cold climates.
How an ice dam forms:
- Warm air from a heated attic warms the roof deck, melting snow on the upper portion of the roof.
- Meltwater runs down the slope toward the eaves.
- The eaves extend over unheated space (soffits) and are colder — the water refreezes here, forming a dam of ice.
- Subsequent meltwater backs up behind the dam and forces itself under the shingles, through nail holes in standard felt, and into the attic or wall.
Why self-adhering shield works: Unlike felt (which has unfilled nail holes), ice-and-water shield seals around every fastener. Even when water is driven sideways or uphill by hydraulic pressure behind the dam, the self-sealing membrane prevents penetration. The IRC requires coverage of at least 24 inches inside the warm wall line specifically to address this mechanism.
The long-term fix for ice dams is air-sealing the attic and adding insulation to keep the deck uniformly cold — but self-adhering shield is the correct roofing response that protects the home while attic improvements are pending.
Underlayment for metal roofing: different rules
Metal roofing cannot use the same underlayment products as asphalt shingles. The thermal expansion and contraction of metal panels (which can move 1–2 inches over a roof span with temperature changes) creates friction against the underlayment — and standard felt will bond to the metal’s underside and tear as the metal moves.
| Product type | Cost | Best for | Notes |
|---|---|---|---|
| High-temp synthetic (metal-rated) | $0.55–$0.90/sq ft | Standing seam, exposed-fastener panels | Resists up to 250°F+ surface temp; non-bonding surface |
| Vented / dimple mat underlayment | $0.70–$1.20/sq ft | Standing seam on low-slope or hot climates | Creates air gap; allows moisture vapor to escape |
| Rubberized asphalt (metal-rated) | $0.80–$1.30/sq ft | Steel shingles, corrugated panels | Self-sealing; rated for movement tolerance |
| Standard asphalt felt 15-lb | Not recommended | — | Bonds to metal underside; tears as metal moves; voids most warranties |
Manufacturer warranty requirements by brand
Using a non-approved underlayment product can void a manufacturer’s material warranty — even if the underlayment performs adequately. This matters most when you are paying for a premium system warranty. Here is what the major shingle manufacturers require:
GAF (Timberline, Designer)
Standard warranty: Minimum: GAF FeltBuster or GAF ProStart (15-lb equiv.) or any ASTM D226 Type I underlayment
System warranty: GAF Golden Pledge / Silver Pledge: requires GAF Deck-Armor, GAF WeatherWatch (ice & water), and GAF RoofPro or Master Elite installer
Using non-GAF underlayment on a job going for Golden Pledge warranty is the most common approval failure.
Owens Corning (Duration, TruDefinition)
Standard warranty: Minimum: any synthetic underlayment or 15-lb felt meeting ASTM D226
System warranty: Platinum Protection: requires OC WeatherLock self-adhering + OC synthetic underlayment; installer must be Platinum-certified
OC Platinum warranty covers both materials AND workmanship — the strongest residential coverage available.
CertainTeed (Landmark, Landmark Pro)
Standard warranty: Minimum: 15-lb felt or any synthetic; CertainTeed SureStart underlayment for system warranty eligibility
System warranty: SureStart PLUS: requires CertainTeed WinterGuard + CertainTeed underlayment + certified installer
CertainTeed offers a 50-year non-prorated warranty for SureStart PLUS systems.
Malarkey (Vista, Legacy)
Standard warranty: Minimum: synthetic underlayment (specifically recommends Malarkey AnchorGard)
System warranty: Premium system warranty requires Malarkey AnchorGard synthetic; any self-adhering membrane at eaves and valleys
Malarkey has stricter synthetic requirements than some competitors — felt is not recommended on their profiles.
What to ask about underlayment in a roofing quote
What underlayment type is included?
Is it 15-lb felt, 30-lb felt, or synthetic? Most modern installs use synthetic — if a quote specifies 15-lb felt, ask why and whether an upgrade is available.
Is ice-and-water shield included at the eaves?
In northern states, this is code-required. In southern states, ask whether valleys are covered with self-adhering membrane — this is best practice everywhere.
What is the manufacturer warranty requirement?
Some shingle warranties (e.g., GAF's Golden Pledge) require specific underlayment products. Using non-approved underlayment may void the system warranty.
What is the upgrade cost for full synthetic vs. felt?
The difference on a 20-square roof is typically $200–$600. This is usually worth paying — ask for a line-item breakdown.
Frequently asked questions
What is roof underlayment and do I need it?↓
What is the best roof underlayment?↓
How much does roof underlayment cost?↓
Do I need underlayment under metal roofing?↓
How long does roof underlayment last?↓
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