Old roofing felt, or tar paper, sits beneath shingles or tiles and acts as a moisture barrier. Whether to remove it during a roof replacement or repair depends on its condition, age, and how it interacts with newer underlayments. This guide explains when removal is wise, potential risks of leaving old felt in place, and practical steps for a safe, durable roof retrofit tailored to American homes.
Understanding Roofing Felt and Its Role
Roofing felt is an underlayment that provides an extra layer of protection against moisture intrusion. Traditional organic felt dampens water and offers some insulation, but it can degrade over time, absorb moisture, and become less effective. Modern roofs often use synthetic underlayments that are lighter, more durable, and resistant to tearing. The choice between preserving or removing old felt is influenced by the roof’s age, climate, and the type of new underlayment planned.
When to Consider Removing Old Felt
Consider removal if any of the following apply: significant delamination, curling, or mold growth; persistent leaks despite other repairs; or the old felt is damaged by pests or moisture. If the existing felt is more than 15–20 years old and shows wear, removal is often prudent, especially when upgrading to a modern synthetic underlayment. Removing old felt can improve ventilation, reduce trapped moisture, and ensure the interior warranty for the new roof remains intact.
Risks of Leaving Old Felt In Place
Leaving deteriorated felt can create hidden problems. Deterioration can trap moisture against the roof deck, promoting wood rot, the growth of mold or mildew, and fungal decay. In areas with high humidity or heavy rainfall, moisture accumulation under old felt may compromise sheathing and framing. Additionally, some older felts contain asbestos fibers in the past; if a home has vermiculite or asbestos-containing materials, handling requires professional guidance. For an American homeowner, these risks justify careful assessment before deciding to retain the old layer.
Assessing the Roof Deck Condition
Before removal, inspect the roof deck for signs of damage. Look for soft spots, cupping, or staining on plywood or oriented strand board (OSB). A damaged deck can require replacement, which increases cost but improves long-term performance. If the deck is sound and the existing underlayment is not excessively deteriorated, removal may focus on upgrading to a higher-quality underlayment rather than a complete deck replacement. A professional roofer can perform a moisture reading and confirm deck integrity.
Removal Process: Step-by-Step
The removal process should be performed by a qualified roofing professional. Typical steps include:
- Protective preparation and containment to limit dust and debris.
- Removal of old shingles to expose the felt and deck.
- Careful lifting and removal of the felt without damaging the deck.
- Inspection of the deck for damage, mold, or rot, with immediate repairs as needed.
- Cleaning and preparation of the deck surface for the new underlayment, including drying time if moisture is present.
- Installation of the chosen underlayment, ensuring proper overlaps and fastener depth.
Choosing the Right Underlayment After Removal
After removing old felt, select an underlayment that fits the roof type and climate. Options include:
- Asphalt-saturated felts for traditional asphalt shingle roofs, though less common with newer building codes.
- Synthetic underlayments offering superior water resistance, lighter weight, and easier installation.
- Self-adhering membranes for high-wind zones or roofs with complex details.
- Ventilated or air-permeable underlays that improve condensation management when combined with proper roof ventilation.
Note: Some regions require wind-rated or code-compliant underlayments. Local building codes and manufacturer guidelines should be consulted to ensure compatibility and warranty coverage.
Impact on Insulation, Ventilation, and Energy Efficiency
Removing old felt and installing a modern underlayment can improve roof ventilation and reduce moisture buildup. In colder climates, better moisture management can minimize ice dam risks, while in hot climates, high-quality synthetic underlayments can contribute to overall energy efficiency by reducing heat transfer. While underlayment itself has a limited role in insulation value, ensuring a dry, well-ventilated roof assembly supports long-term energy performance and indoor air quality.
Cost and Labor Considerations
Removal costs vary by roof size, complexity, and local labor rates. Expect higher costs for roofs with multiple penetrations or steep pitches. Removing old felt adds labor time, deck inspection, and potential deck repairs. However, the long-term benefits—reduced moisture risk, enhanced warranty coverage, and improved durability—often justify the expense. Getting multiple written estimates helps compare the cost of removal versus retaining the old layer when appropriate, plus the price of the chosen underlayment.
Safety and Environmental Considerations
Roof work carries fall hazards and exposure to dust, solvents, and old materials. Use proper fall protection, PPE, and decline to work on wet or icy roofs. If asbestos-containing materials are suspected, professional abatement is required by regulations. Proper disposal of old felt and damaged decking should follow local requirements. A licensed roofer can navigate these safety and environmental concerns effectively.
Best Practices for a Durable Outcome
For a durable result when old felt is removed, consider these best practices: conduct a thorough deck inspection, match underlayment to climate and roof type, ensure correct overlaps and fastener patterns, and verify ventilation and attic access. Schedule inspections after installation to confirm there are no gaps or lapses in waterproofing. Documentation for warranties and code compliance should be kept for future reference.
Common Scenarios and Recommendations
Scenario 1: A 20-year-old asphalt shingle roof in a humid region with visible felt deterioration. Recommendation: Remove old felt, inspect the deck, and install a high-quality synthetic underlayment.
Scenario 2: A roof with minimal felt wear and a modern underlayment already installed. Recommendation: If the deck is sound and the current underlayment meets code, removal may not be necessary, but confirm compatibility with the new roofing material.
Scenario 3: Historical homes or complex roofs with unique venting. Recommendation: Consult a restoration specialist to balance preservation, performance, and codes while possibly retaining authentic materials where feasible.
Final Considerations
Ultimately, whether to remove old roofing felt depends on the condition of the felt, the deck, and the planned replacement materials. Removal can reduce moisture problems and support modern performance, but it adds cost and labor. A professional assessment is essential to determine if removal, deck repair, or a full re-roof with modern underlayment best serves the home’s safety, efficiency, and longevity.