Tar Paper Roof Leaking: Causes, Repairs, and Prevention

A tar paper roof, or built-up roof with mineral-surfaced roofing felt, can develop leaks from aging, weather exposure, or improper installation. Understanding common failure points and practical repair steps helps homeowners and property managers address leaks effectively. This article outlines the causes, inspection steps, repair options, and long-term prevention strategies for tar paper roofs in the United States.

What Is Tar Paper Roofing

Tar paper roofing uses asphalt-impregnated asphalt-saturated felt (tar paper) as an underlayment or as part of a built-up roof system. The felt provides a waterproof barrier beneath layers of roofing material, such as coal tar or asphalt, and helps shed moisture. Over time, aging, UV exposure, and thermal cycling can degrade the felt, leading to leaks. In many homes and commercial buildings, tar paper underlayment is a foundational layer, making proper installation and maintenance crucial for long-term performance.

Common Causes Of Leaks In Tar Paper Roofs

Leaks in tar paper roofs typically arise from a combination of wear and installation issues. Common culprits include punctures from foot traffic or equipment, degraded flashing around chimneys, vents, and skylights, and insufficient or damaged sealants. Thermal movement can cause seams to open, while ponding water on flat areas accelerates underlayment deterioration. Inspectors often find failed nails, loose gravel ballast, and wind-driven damage at edges and parapets. Addressing these issues early reduces interior water intrusion and structural damage.

Inspection And Detection

Thorough inspection starts on the exterior and extends to attic spaces. Look for dark, damp, or stained areas on ceilings and walls, which indicate active leaks. Outside, check for cracked, blistered, or lifted tar paper, missing granules, and exposed felt. Inspect flashing around penetrations and roof-to-wall transitions. In the attic, search for mold, musty odors, or staining along roof lines. Use a flashlight to reveal water staining and trace leaks to their source. Document damage with photos to guide repairs and insurance claims.

Repair Options For Tar Paper Roof Leaks

Repair approaches vary with leak extent and roof design. Minor leaks may be addressed by resealing seams, replacing damaged felt, or patching punctures with compatible roofing cement or mastic. For more extensive damage, a partial or complete re-roof may be necessary, including reinstalling tar paper underlayment and resealing flashing systems. When feasible, upgrade to a modern membrane or cap sheet system for improved durability. All repairs should restore a continuous weatherproof barrier and ensure proper drainage.

• Puncture Repair: Clean and dry the area, apply roofing cement, and embed a patch compatible with tar paper.
• Seam Re-Clication: Re-seal exposed seams using asphalt-based sealant and flashing adjustments.
• Flashing Replacement: Remove damaged flashing, clean substrate, install new flashing, and seal joints watertight.
• Partial Re-Roof: Remove damaged sections and install new underlayment and cap sheets to restore integrity.
• Full Re-Roof: When widespread damage exists, install a modern membrane system for long-term performance.

Maintenance And Prevention

Proactive maintenance extends tar paper roof life and minimizes leaks. Schedule annual inspections, especially after severe weather, and clean gutters to prevent water backup. Keep foot traffic off delicate areas and use proper safety measures when accessing roofs. Maintain proper roof slope and ensure drainage directs water away from vulnerable edges. Consider upgrading to modern underlayment or membrane systems that offer enhanced waterproofing, UV resistance, and wind uplift performance. Document inspections and repairs for future reference and resale value.

When To Call A Professional

While minor repairs can often be DIY, professionals should handle complex leaks, extensive damage, or structural concerns. If interior water intrusion persists after initial repairs, if there is visible sagging or widespread blistering, or if attic moisture persists, consult a licensed roofing contractor. A pro can assess substrate integrity, verify ventilation adequacy, and recommend best long-term solutions consistent with local codes and insurance requirements. For cost estimates, obtain multiple written bids that include material types, warranty coverage, and expected project timelines.