How to Repair Roof Felt: A Complete Guide to Fixing Damaged Roofing Felt in 2025

Roofing felt, often found under shingles or on shed roofs, is a critical component of your roof’s protective system. It acts as a barrier against moisture, helps prevent leaks, and extends the life of your roof. But like all materials exposed to the elements, roof felt can deteriorate over time—especially in extreme weather conditions.

If you’re asking “how to repair roof felt,” you’re likely dealing with a leak, blistering, cracking, or visible tears. Don’t worry—this comprehensive guide will walk you through everything you need to know to confidently repair roof felt yourself or know what to expect from a professional repair job.

What Is Roof Felt?
Why Roof Felt Gets Damaged
Signs You Need to Repair Roof Felt
Tools and Materials Needed for Roof Felt Repair
Safety Tips Before You Begin
Step-by-Step Guide to Repair Roof Felt
Repairing Roof Felt Under Shingles
Repairing Flat Roof Felt
When to Replace Instead of Repair
Preventive Tips to Extend Roof Felt Lifespan
Roof Felt FAQs
Conclusion

1. What Is Roof Felt?

Roof felt, also known as roofing underlayment or tar paper, is a protective layer installed between your roof deck and the outer roofing material—such as shingles or tiles. It is usually made from:

Organic paper saturated with asphalt
Fiberglass mat saturated with bitumen
Bitumen-based roll materials (on flat roofs)

Roof felt provides secondary protection against water intrusion. It’s particularly crucial for preventing leaks when roofing materials are damaged or compromised.

2. Why Roof Felt Gets Damaged

Roof felt is built to last, but over time, several factors can degrade it:

UV exposure: Sunlight breaks down felt, especially if exposed directly without shingle coverage.
Water intrusion: Standing water or ice dams cause felt to deteriorate faster.
Physical damage: Wind-blown debris, fallen branches, or foot traffic can tear felt.
Age: As roofing felt ages, it becomes brittle, making it more prone to cracks and holes.
Improper installation: Poor overlaps, loose edges, or nails that create tears can all lead to early failure.

3. Signs You Need to Repair Roof Felt

If you notice any of the following signs, your roofing felt may be damaged and in need of repair:

Leaks inside the home during rain
Sagging or soft areas on the roof
Blistering or bubbling on flat roof surfaces
Visible tears or cracks on exposed felt (often seen on sheds or garages)
Damp patches on ceilings or upper walls
Loose or displaced roofing material revealing the underlayment

4. Tools and Materials Needed for Roof Felt Repair

Before starting a roof felt repair project, gather these tools and materials:

Tools:

Utility knife or roofing knife
Hammer or staple gun
Trowel
Roofing nail puller or pry bar
Tape measure
Ladder with safety stabilizers
Safety harness (for pitched roofs)

Materials:

Roofing felt (match the existing type)
Roofing nails or staples
Roofing adhesive or bitumen sealant
Roofing cement or mastic
Waterproof patch or repair membrane (for flat roofs)
Aluminum flashing (if necessary)

5. Safety Tips Before You Begin

Always work on a dry roof—wet surfaces are slippery and dangerous.
Use a properly stabilized ladder on level ground.
Wear non-slip boots and a safety harness if working on pitched roofs.
Avoid roof work during windy or rainy conditions.
Know your limits—call a professional if the roof is too steep or damaged.

6. Step-by-Step Guide to Repair Roof Felt

This section outlines how to repair exposed roofing felt, such as on a shed or flat roof. If your felt is beneath shingles, jump to section 7.

Step 1: Inspect the Damage

Locate the damaged area. Look for:

Tears or cracks
Loose felt along edges
Bubbles or blisters
Areas where water is pooling

Mark the damaged section with chalk or masking tape for clarity.

Step 2: Remove the Damaged Felt

Using a utility knife, carefully cut around the damaged felt. Remove it cleanly without tearing surrounding material. If nails or staples are holding it, use a pry bar or hammer to remove them.

Step 3: Clean and Dry the Area

Clear the area of dirt, debris, or standing water. A clean surface ensures a strong bond when applying new felt or adhesive.

Step 4: Cut Replacement Felt

Measure the area needing repair and cut a new piece of felt that’s about 2–3 inches larger on all sides. This overlap helps ensure a watertight seal.

Step 5: Apply Roofing Adhesive

Using a trowel or brush, apply a generous amount of roofing cement or bitumen adhesive around the perimeter of the cutout and across the exposed roof deck.

Step 6: Install New Felt Patch

Carefully lay the new piece of felt over the adhesive. Press firmly to secure it in place. Use roofing nails or a staple gun along the edges for added hold.

Step 7: Seal the Edges

Apply roofing cement along the edges of the patch using a putty knife. Spread it evenly and feather the edges to prevent water penetration.

Step 8: Inspect and Test

Check that the patch is smooth, well-sealed, and fully adhered. After 24–48 hours, check again after a rainstorm to ensure it’s holding up.

7. Repairing Roof Felt Under Shingles

When roofing felt beneath shingles is damaged, the process is more complex because you must temporarily remove some shingles to access the felt.

Step-by-Step Process:

Locate the leak or damage using attic inspection or water stains.
Remove the shingles above the damaged felt using a pry bar.
Cut out the damaged felt without disturbing too much of the surrounding material.
Install new felt with at least a 6-inch overlap.
Reinstall or replace shingles and seal them properly with roofing nails and adhesive.
Check flashing nearby to ensure it’s intact.

This type of repair is best left to professionals unless you’re experienced with roofing.

8. Repairing Flat Roof Felt

Flat roof felt is common on garages, extensions, and outbuildings. It’s often a three-layer torch-on felt system or single-layer bitumen roll.

Blister Repair:

Cut a slit in the blister to release trapped air or moisture.
Dry the area thoroughly using a heat gun or by waiting.
Apply roofing cement inside the blister.
Press the felt down and roll it flat.
Nail or weigh it down for several hours.
Cover the area with a new patch and seal all edges.

Tear or Hole Repair:

Trim the damaged section neatly.
Clean and dry the area.
Apply roofing cement or torch-on felt patch.
Roll and press the patch until flat.
Apply an additional coat of bitumen sealant over edges.

9. When to Replace Instead of Repair

Repairing is cost-effective, but not always the best long-term solution. Consider full replacement when:

The felt is more than 15–20 years old
There are multiple leaks across different areas
The felt has become brittle or is deteriorating widely
You’ve already patched the same area multiple times
You’re re-roofing or replacing tiles/shingles anyway

10. Preventive Tips to Extend Roof Felt Lifespan

Inspect your roof regularly for early signs of wear.
Clear debris like leaves and branches from the roof.
Fix gutter problems to prevent water overflow onto the roof.
Apply a protective coating to exposed flat felt roofs every few years.
Avoid foot traffic on felt surfaces when unnecessary.

11. Roof Felt Repair FAQs

How long does roof felt last?

Standard roofing felt lasts 10–20 years, depending on the type and exposure to elements.

Can I repair roof felt myself?

Yes—if it’s minor damage on an accessible, flat, or low-slope roof. For steep, high, or complex repairs, hire a professional.

Is it better to patch or replace roof felt?

Patching is fine for isolated damage. Replacement is better for widespread deterioration.

Does roof felt go under shingles or on top?

Under. Felt is the underlayment layer, installed before the final roofing material like shingles or tiles.

What is the best adhesive for roof felt repair?

Bitumen-based adhesives or roofing cements are most effective for sealing and adhering felt.

12. Conclusion

Roof felt plays a vital role in keeping your roof watertight and durable. When it’s damaged, timely repair prevents more serious issues like leaks, mold, and structural decay.

Whether you’re dealing with a minor tear in your shed roof or replacing underlayment beneath shingles, knowing how to repair roof felt empowers you to act quickly and confidently. Follow the step-by-step instructions in this guide, observe proper safety practices, and don’t hesitate to call in a professional for complex or high-risk repairs.

Remember—early attention to small issues can save you thousands in future roof repairs or full replacements.