Roofing felt, a traditional asphalt-saturated design, is widely used as a underlayment beneath shingles. Many homeowners wonder if it can be repurposed as a wall barrier or weather protection. This article explains whether roofing felt can be used on walls, how it should be installed, and what safer, code-compliant alternatives exist for wall applications in the United States.
What Is Roofing Felt and Its Typical Role
Roofing felt is a flexible, paper-like sheet treated with asphalt to resist moisture. Its primary function is to provide an extra layer of protection against wind-driven rain and to help seal the roof deck before shingles are installed. It is designed to be installed on rooftops where it will be exposed to sunlight, weather, and temperature fluctuations during construction before the final roofing material goes on. On walls, however, roofing felt faces different exposure and performance requirements that it is not optimized to meet.
Can Roofing Felt Be Used On Walls?
In most cases, using roofing felt on exterior walls is not recommended as a primary weather-resistive barrier. Building codes in many U.S. jurisdictions require a purpose-built wall barrier, often called a weather-resistant barrier (WRB) or building wrap, that is specifically rated and tested for wall assemblies. Roofing felt lacks the required tear resistance, UV durability, and modern drainage characteristics essential for walls. If roofing felt is used on walls, it should be temporary, protected from direct UV exposure, and part of a broader installment plan that includes proper WRB and exterior cladding.
Pros And Cons Of Using Roofing Felt On Walls
- Pros: Simple material, familiar to builders, low cost, easy to cut, offers some moisture protection when used as a windbreak.
- Cons: Poor UV resistance when exposed, limited durability against wind-driven rain on large wall surfaces, not approved as a primary WRB in most codes, limited performance in high-humidity or high-rain climates, potential for slippage or tearing during wind events, may trap moisture if not installed with proper drainage and drainage-enabled sheathing.
How To Use Roofing Felt On Walls Safely (If At All)
If a project still requires or tolerates temporary use of roofing felt on walls, follow these cautious practices. Note that local code requirements may override these guidelines, and a professional should confirm compliance.
- Temporary or interior use only: Use roofing felt only as a temporary barrier during construction, not as a permanent WRB.
- Protect from UV: Do not leave felt exposed to sunlight for extended periods. If used outdoors, cover with a breathable weather barrier or immediate cladding.
- Seam protection: Overlap seams in the direction of anticipated water flow and seal with compatible tape; ensure seams are well-protected by the exterior finish.
- Ventilation and drainage: Ensure there is a proper drainage plane behind the wall finish to prevent moisture buildup behind the felt.
- Limit exposure: Use roofing felt only behind non-porous or low-porosity siding materials and avoid areas with high vapor pressure or significant temperature variation.
Safer, Code-Approved Alternatives For Wall Weather Barriers
To align with best practices and building codes, consider these alternatives for exterior walls:
- House Wrap / Weather-Resistive Barriers (WRB): Materials like Tyvek, Typar, or similar WRBs are specifically engineered for walls, providing water resistance while allowing vapor diffusion.
- Building Paper: Heavier, more durable than standard roofing felt, designed for wall assemblies and installed with proper drainage and overlap.
- Rigid Foam Sheathing With Air Gap: For energy efficiency, exterior rigid foam insulation plus a drainage plane behind the cladding can improve insulation and moisture management.
- Drainage-Enabled Cladding Systems: Siding products with built-in drainage channels or ventilated rain screens help manage moisture more effectively than roofing felt on walls.
When choosing wall protection, the following practice tips help ensure performance and longevity:
- Follow manufacturer specs: Always follow WRB and siding manufacturer installation instructions, including overlaps, fastener types, and sealants.
- Ventilation matters: Maintain an air gap behind the cladding to promote drying and prevent moisture buildup.
- Seal penetrations: Seal around windows, doors, and vent penetrations with compatible flashing and tapes to prevent water intrusion.
- Quality control: Inspect for tears, voids, and holes in the barrier during installation and repair promptly.
- Climate considerations: In regions with strong wind-driven rain or heavy humidity, stronger WRBs and cladding systems are especially important.
Maintenance is key to wall durability. Regular inspections after storms or seasonal changes help detect moisture intrusion or damaged barriers. If moisture is found behind any exterior finish, address it immediately to prevent mold, rot, or structural issues. Roofing felt, if used at all on walls, should be a temporary measure and replaced with a proper WRB and finished with approved cladding as soon as feasible.
Frequently Asked Questions
- Is roofing felt on walls a good long-term solution? No. It is not designed for long-term weather resistance on walls and often does not meet code requirements for exterior barriers.
- What should I use instead of roofing felt for walls? A purpose-made weather-resistive barrier or building wrap, combined with a proper drainage plane and suitable siding.
- Can I apply roofing felt over masonry or concrete walls? Generally not recommended; consult local codes and a building professional for alternatives appropriate to the wall substrate.