Types of Roofing Paper: Guide to Felt, Underlayment, and Synthetic Options

Roofing paper is a critical component of a durable roof system, providing moisture resistance, secondary protection, and a smooth surface for shingles. This guide explains common types of roofing paper, their performance differences, installation considerations, and how to choose the right material for residential and light commercial roofs in the United States. Understanding these options helps homeowners and contractors make informed decisions that affect longevity, code compliance, and warranty coverage.

Type	Common Names	Key Benefits	Typical Uses
Asphalt-Saturated Felt	Tar Paper, Felt Paper (15# / 30#)	Economical, time-tested, easy to install	Traditional roofing underlayment for shingles
Rubberized Asphalt	Self-Adhered Underlayment, Peel-and-Stick	Superior waterproofing, air-sealing, ice dam protection	Eaves, valleys, low-slope roofs, high-risk areas
Non-Bitumen Synthetic	Synthetic Underlayment	Lightweight, tear-resistant, breathable options	Roof decks under shingles, high-wind regions
Ice And Water Shield	Self-Adhered Membrane	Strong adhesion, seals around fasteners	Eaves, rakes, valleys, penetrations

What Is Roofing Paper And Why It Matters

Roofing paper, also called underlayment, is a protective layer installed between the roof deck and the exterior roofing material. It acts as a secondary barrier against water intrusion, protects the deck during shingle replacement, and can improve fire resistance and wind performance. Underlayment also creates a smoother surface for shingle installation and may be required by building codes for certain roof slopes.

Asphalt-Saturated Felt (Traditional Tar Paper)

Asphalt-saturated felt is the classic roofing paper available primarily in 15-pound (15#) and 30-pound (30#) weights. It consists of a felt base saturated with asphalt or bitumen. Its main advantages are cost-effectiveness and broad historical use, which makes it compatible with most shingle systems.

Characteristics And Performance

15# felt is lighter and easier to handle but less durable; 30# felt is thicker with better tear resistance and water holdout. Both types can absorb moisture and deteriorate if left exposed for long periods. They provide basic secondary protection but are not fully waterproof.

Installation And Best Uses

Felt is typically installed in overlapping horizontal courses and nailed to the roof deck. It is suitable for standard asphalt shingle installations on slopes greater than the minimum allowed by code. It remains popular for budget-sensitive projects and where long exposure to weather is not expected.

Rubberized Asphalt Underlayment (Self-Adhered)

Rubberized asphalt underlayment is a peel-and-stick membrane with a sticky rubberized bitumen backing and a factory-applied release liner. This product provides a watertight seal, adheres to the deck, and can seal around nails and fasteners.

Performance Benefits

Rubberized membranes offer superior waterproofing, making them ideal for eaves, valleys, hips, and roof penetrations. They perform well in areas prone to ice dams and heavy rain, reducing the risk of water intrusion under shingles.

Applications And Considerations

Because of cost, rubberized asphalt is often used selectively in critical areas rather than across an entire roof. Proper deck preparation and temperature considerations during installation are crucial to ensure adhesion and performance. Many manufacturers recommend it for ice-and-water protection zones defined by local codes.

Synthetic Underlayment

Synthetic underlayment is made from polypropylene or polyethylene woven or non-woven fabrics coated for weather resistance. It has become a popular alternative to felt. Key advantages include higher tensile strength, better tear resistance, and lower weight per roll.

Types And Features

Synthetic products range from basic non-bitumen slip sheets to higher-end breathable membranes with engineered water-shedding layers. Some synthetics include skid-resistant surfaces, UV resistance for extended exposure, and engineered lap designs for fast installation.

When To Choose Synthetic Underlayment

Synthetics are well-suited for steep-slope roofs, long deck exposures during construction, and high-wind areas where tear resistance matters. They often enhance contractor productivity and reduce jobsite damage compared to felt. Compatibility with shingle adhesives and manufacturer warranties should be verified.

Ice And Water Shield: High-Performance Membranes

Ice and water shield membranes are specialized self-adhering rubberized asphalt products designed to prevent water migration around roof edges and penetrations. They are commonly mandated by building codes in colder climates for eave and valley protection.

Key Attributes

These membranes bond tightly to the roof deck and can seal around nails and staples, preventing leaks caused by ice dams or wind-driven rain. They are especially useful under shingles at low-slope transitions and roof-to-wall interfaces.

Limitations And Best Practices

Ice and water shield is thicker and more costly, so it’s typically used in targeted zones rather than entire roofs. Surface cleanliness and temperature during application significantly influence adhesion and long-term performance.

Breathability And Vapor Considerations

Roof underlayment choices affect the roof’s ability to manage moisture vapor. Felt is relatively non-breathable; some synthetics offer vapor-permeable options. Choosing the right underlayment depends on attic ventilation, climate, and the roofing system’s overall moisture management strategy.

Vapor-Permeable Options

Vapor-permeable synthetics allow moisture vapor to escape from the deck while still shedding liquid water. These are useful in mixed climates or when retrofit insulation increases condensation risk. Contractors should coordinate underlayment selection with attic ventilation design.

Code Requirements And Manufacturer Warranties

Local building codes often specify underlayment requirements by roof slope and climate zone. Manufacturer shingle warranties may require specific underlayment types for full coverage. Verifying local code mandates and warranty conditions before selecting roofing paper avoids costly noncompliance.

Inspection And Documentation

Keep product data sheets and installation instructions on site during installation. Inspectors and warranty providers often require evidence that the recommended underlayment and installation details were followed exactly.

Cost Comparison And Lifespan

Cost varies widely: asphalt felt is least expensive, synthetic underlayment costs more, and rubberized asphalt or ice-and-water shield is highest per square. Lifespan depends on exposure, product quality, and installation; synthetic underlayments and rubberized membranes generally outlast felt in durability and UV exposure tolerance.

Underlayment Type	Relative Cost	Typical Lifespan
Asphalt-Saturated Felt	Low	5–25 Years (exposure-dependent)
Synthetic Underlayment	Medium	15–50 Years (product-dependent)
Rubberized Asphalt / Ice & Water Shield	High	25–50+ Years (when properly installed)

Installation Tips And Common Mistakes

Correct installation ensures underlayment performance. Use proper fasteners, follow manufacturer lap requirements, and avoid leaving underlayment exposed to sunlight longer than recommended. Common mistakes include insufficient overlap, improper sealing at penetrations, and applying self-adhered membranes at temperatures below manufacturer limits.

Fastening And Seams

Cap nails or staples designed for underlayment should be used per instructions. For synthetic and felt products, shingle manufacturers may prescribe placement of fasteners to avoid tearing and wind uplift issues. Self-adhered membranes require smooth, clean substrates for full adhesion.

Environmental And Safety Considerations

Synthetic underlayments reduce waste and can be lighter to transport, lowering jobsite footprint. Asphalt-based products contain bitumen and have different disposal considerations. Contractors and homeowners should balance performance needs with environmental preferences and local disposal regulations.

Handling And Jobsite Safety

Roofing paper can be slippery when wet; using footwear with good traction and fall protection is essential. Self-adhered rolls can be heavy—use proper lifting techniques and team handling to reduce injury risks.

How To Choose The Right Roofing Paper

Select underlayment based on climate, roof slope, exposure duration, budget, and shingle warranty requirements. For critical areas and colder climates, prioritize rubberized or ice-and-water products; for whole-roof applications in many regions, high-quality synthetic underlayment offers longevity and performance advantages over felt.

Checklist For Selection

• Verify local building code underlayment and ice-and-water requirements.
• Check shingle manufacturer warranty requirements.
• Consider wind uplift ratings for high-wind zones.
• Account for roof slope and roof deck condition.
• Balance initial cost with expected lifespan and exposure time.

Frequently Asked Questions About Roofing Paper

How Long Can Underlayment Be Exposed? Most felts can tolerate short exposure, while synthetics can last longer; follow manufacturer exposure limits. Extended exposure can lead to degradation and reduced performance.

Can Synthetic Replace Felt For Warranties? Many shingle manufacturers accept approved synthetics, but homeowners should confirm that substitution will not void warranties. Documentation and product approvals are essential.

Is Peel-And-Stick Necessary Everywhere? Peel-and-stick is vital in vulnerable areas like eaves and valleys but may be overkill for full roof application except on low-slope roofs. Targeted use often achieves the best cost-to-protection balance.

Resources And Further Reading

Consult local building codes, manufacturer installation guides, and professional roofing contractors for specific project guidance. Reliable sources include the International Code Council (ICC), National Roofing Contractors Association (NRCA), and product technical data sheets.