Best Tar Paper for Roofing: Choosing Durable Underlayment for Lasting Protection

The following guide helps homeowners and contractors choose the best tar paper for roofing, comparing weight, durability, installation, and cost to match project needs and climate considerations.

Type	Weight	Best Use	Pros	Cons
15# Felt (Organic)	15 lb	Budget residential	Affordable, easy to work	Less durable, rots if wet
30# Felt (Fiberglass)	30 lb	Most residential	Durable, stable, tear-resistant	Heavier, higher cost
Synthetic Underlayment	Lightweight (varies)	High performance	Water-resistant, UV-stable	More expensive, slippery

Why Choosing The Right Tar Paper Matters

Tar paper, also called roofing felt or underlayment, acts as a secondary weather barrier beneath shingles. Selecting the best tar paper for roofing reduces wind-driven rain intrusion, protects decking during installation, and adds fire and thermal resilience.

Quality underlayment extends roof life, prevents premature shingle wear, and can influence warranty eligibility from shingle manufacturers. The right choice depends on climate, roof slope, and budget.

Types Of Tar Paper And Underlayment

Organic Felt

Organic felt is made from cellulose (paper) saturated with asphalt. It is available in 15# and older 30# weights. Organic felt is affordable and familiar to many roofers but absorbs moisture and may deteriorate over time, making it less suitable in humid or wet climates.

Fiberglass Felt

Fiberglass felts use a nonwoven fiberglass mat coated with asphalt. Fiberglass 30# felt is a common industry choice because it resists tearing, holds fasteners better, and remains dimensionally stable. Fiberglass felt offers a balance of cost and durability ideal for most residential installations.

Synthetic Underlayment

Synthetic underlayments are polypropylene or polyester laminates coated for UV resistance. They provide superior water resistance, lighter weight, and increased tear strength. Synthetics are preferred for long exposures and steep or complex roofs, though they can be pricier and sometimes slippery underfoot.

Weight Ratings And What They Mean

Tar paper is traditionally labeled by weight per square (15# and 30#). The number is a legacy labeling system reflecting weight of 100 square feet of material. 15# is lighter and less durable; 30# is heavier and more resilient. For modern fiberglass and synthetic options, manufacturers use grams per square meter (GSM) or performance specs instead of pound ratings.

Key Performance Factors To Compare

When evaluating the best tar paper for roofing, consider water resistance, tear strength, dimensional stability, UV tolerance, slip resistance, and ease of installation. These factors determine field performance and the roof’s long-term protection.

• Water Resistance: Prevents leak paths under shingles, important in heavy rain or ice dam areas.
• Tear Strength: Reduces damage during installation and resists wind uplift.
• Dimensional Stability: Limits stretching or shrinking that could open seams.
• UV Tolerance: Allows longer exposure before shingles are installed.
• Slip Resistance: Affects worker safety during installation.

Best Choices For Different Situations

Budget Residential Roofs

For homeowners on a budget, 30# fiberglass felt often offers the best value—combining durability with an affordable price. It works well with asphalt shingles in most climates when installed properly with proper flashing and ventilation.

High-Performance Or Long-Exposure Jobs

When decks will be exposed for weeks or in professional installations demanding high performance, synthetic underlayment is usually the top choice due to water resistance and UV stability. Manufacturers offer different classes for high-heat or fire-rated applications.

Steep Or Complex Roofs

Complex roofs with many valleys or steep pitches benefit from the tear strength and slip resistance of high-quality fiberglass felts or slip-resistant synthetic underlayments. Enhanced tear strength reduces the risk of damage during shingling.

Installation Best Practices

Proper installation is as important as material choice. Underlayment should be installed shingle-fashion from the eave up, with manufacturer-recommended overlaps and fastener spacing. Improper installation negates the protective benefits of even the best tar paper.

Key steps include aligning starter courses, using corrosion-resistant roofing nails or staples at specified intervals, and sealing lap edges in exposed locations or valleys. Flashing around chimneys, vents, and eaves must integrate with the underlayment to prevent leaks.

Climate And Local Code Considerations

Climate dictates performance needs: areas with heavy rain, ice dams, or hurricanes require robust water resistance and tear strength. In hot, high-UV regions, a UV-stable synthetic underlayment minimizes degradation during delays. Local building codes may require specific underlayment types or ice-and-water shields in cold climates.

Ice-And-Water Shield Vs. Tar Paper

Ice-and-water shield membranes are self-adhered butyl or SBS-modified asphalt sheets used at eaves and valleys to protect against ice damming and wind-driven rain. They are thicker and adhesive-backed, making them distinct from standard tar paper. Use ice-and-water shield in vulnerable zones and tar paper elsewhere for complete protection.

Common Manufacturer Options And Features

Leading brands offer different formulations and features: traditional asphalt-saturated felts (15# and 30#), fiberglass-reinforced options, and high-performance synthetic underlayments with slip-resistant surfaces. Compare product specs for tensile strength, exposure limits, and warranty terms.

Cost Considerations And Long-Term Value

Material costs vary widely: 15# felt is cheapest, 30# is moderate, and synthetic underlayments cost more but provide added protection. While upfront cost matters, long-term value comes from reduced repair risk, extended shingle life, and fewer weather-related claims.

Safety And Handling Tips

Some felt types can be slippery when wet or dusty. Use fall protection, non-slip footwear, and follow manufacturer recommendations for storage and handling. Synthetics can become slick in sunlight, so take extra precautions on steep slopes. Proper safety measures protect workers and prevent installation damage.

Environmental And Disposal Notes

Organic felts may degrade faster and are more biodegradable than asphalt-heavy or synthetic options. However, all roofing underlayments involve asphalt or polymers and should be disposed of following local waste regulations and recycling options when available. Consider lifecycle impacts when choosing materials.

Frequently Asked Questions

Is 30# Felt Better Than 15#?

Yes, 30# felt is generally more durable and tear-resistant than 15#, making it a better choice for most residential roofs, though modern synthetics can outperform both in many metrics.

Can Synthetic Underlayment Replace Tar Paper?

Yes. Synthetic underlayment often replaces traditional tar paper because of superior water resistance, UV tolerance, and strength, though compatibility with shingle warranties and local codes should be confirmed.

How Long Can Underlayment Be Exposed?

Exposure limits vary by product. Traditional felts may last a few weeks exposed; many synthetics allow longer UV exposure measured in months. Always follow manufacturer exposure limits to avoid material degradation.

How To Choose The Best Tar Paper For Roofing Projects

Assess climate, roof life expectancy, installation schedule, and budget. For most U.S. residential roofs, 30# fiberglass felt or a high-quality synthetic underlayment offers optimal protection. Use ice-and-water shield in eaves and valleys, and follow manufacturer and code requirements for best results.

Consult professional roofers for complex roofs, historic structures, or where specific warranty or code compliance is needed to ensure the chosen underlayment performs as intended.