Using Roofing Felt on Walls: Pros, Cons, and Practical Alternatives
Roofing felt is a time-tested material used as an underlayment in roofing systems, primarily for moisture protection and weather resistance. Homeowners sometimes consider using roofing felt on walls to create a moisture barrier, achieve a certain aesthetic, or meet budget constraints. This article examines whether roofing felt is suitable for wall installations, its limitations, and safer, more effective alternatives. It blends practical guidance with up-to-date considerations for U.S. construction practices and consumer projects.
Key takeaway: While roofing felt offers moisture protection, it is generally not designed for use as exterior wall sheathing or interior wall cladding. Proper wall assemblies require materials rated for walls, with appropriate fasteners, weather barriers, and compliance with local building codes.
What Is Roofing Felt And How Is It Used
Roofing felt, often made from asphalt-impregnated paper or fiberglass reinforced with asphalt, is a flexible, waterproof underlayment installed beneath roof coverings. It helps shed water and protects roofing components during construction and after installation. Roofing felt varies in weight (measured in pounds per 100 square feet) and in permeability. It is designed to tolerate roof slope, wind-driven rain, and UV exposure for limited periods, not long-term wall exposure.
The primary purpose of roofing felt is to act as a secondary barrier beneath shingles, tiles, or other roofing materials. It is not engineered to endure the environmental stresses typical of exterior walls, such as constant sun exposure, temperature swings, abrasion from wind-blown debris, and movement from building settling.
Can Roofing Felt Be Used On Walls?
In most cases, roofing felt is not recommended as a primary wall barrier or as wall cladding. Standard wall assemblies require weather barriers, air barriers, and sheathing rated for exterior or interior use. Roofing felt lacks the durability, breathability control, and UV resistance needed for long-term wall exposure. Some projects might use felt in a temporary or interior role, but even then, it is important to confirm compatible coatings and building codes. When used on interiors, it should be protected from nails, screws, and moisture sources to prevent deterioration.
There are niche situations where a roofing felt layer may appear in a wall assembly, such as an improvised moisture barrier behind traditional sheathing during renovations. However, this is typically not advisable as a retrofit strategy due to compatibility and performance concerns with modern house wraps, rainscreens, and exterior insulation finishes.
Applications And Limitations For Walls
- Moisture Barrier Role: Roofing felt offers limited moisture resistance for walls but is not a substitute for purpose-built weather barriers that meet current codes.
- Breathability: Wall assemblies require breathability and drying potential. Felt has inconsistent breathability and can trap moisture, leading to rot or mold in wall cavities.
- Durability: Exterior walls face sunlight, wind, and physical abrasion. Felt deteriorates faster under UV exposure and temperature cycling than materials designed for walls.
- Code Compliance: Building codes specify approved materials for exterior weather barriers (e.g., house wraps, rain screens, or breathable membranes). Roofing felt may not meet these requirements for long-term wall use.
- Interior Applications: If used indoors, felt must be protected from moisture and physical damage. It does not create a finished surface and would require additional finishing layers.
Safer And More Effective Wall Alternatives
- House Wraps And Weather Barriers: Modern synthetic wraps (e.g., polyolefin or non-wovens) provide air and water resistance while allowing vapor diffusion.
- Rainscreen Systems: A ventilated gap behind the cladding improves drainage and drying, reducing moisture risk.
- Sheathing And Exterior Cladding: Exterior-grade plywood, OSB, or structural insulated panels with appropriate finishes offer structural support and moisture management.
- Vapor Barriers: In climate-specific installations, vapor barriers are placed strategically to manage humidity and condensation.
- Interior Wall Moisture Control: For interior walls, use approved drywall or paneling with vapor control as required by the local climate and building codes.
Installation Considerations If Roofing Felt Is Being Considered Temporarily
If a homeowner is evaluating a temporary or emergency scenario where roofing felt is part of a wall detail, consider these precautions:
- Limit Exposure: Do not leave roofing felt exposed to the elements for extended periods on exterior walls. Cover or replace with an approved wall barrier as soon as feasible.
- Seal And Fasten Properly: If used temporarily on interior walls, ensure edges are sealed to prevent moisture intrusion and that fasteners do not create punctures that compromise the barrier.
- Ventilation And Drying: Maintain proper ventilation to prevent condensation behind the wall assembly, especially in high-humidity areas.
- Consult Local Codes: Check local building codes and manufacturer guidelines before proceeding with any non-standard material on walls.
Maintenance And Durability Implications
Roofing felt is not designed for long-term exterior wall wear. Over time, UV exposure, moisture intrusion, and thermal cycling can cause shrinkage, brittleness, or delamination. In walls, these problems may lead to gaps, energy loss, cold bridges, and potential mold growth if moisture becomes trapped. Regular inspections are essential in any atypical application, but best practice is to rely on materials specifically rated for wall use.
How To Choose The Right Wall Barrier
For exterior walls, prioritize materials that balance moisture protection, air control, and vapor management. A typical modern wall assembly might include:
- Structural sheathing (OSB or plywood)
- Weather-resistant barrier (WRB) such as a certified house wrap
- Air barrier membranes where required by code
- Cladding system with proper drainage and ventilation
For interior walls, select drywall or fire-rated panels finished with appropriate primer and paint, ensuring any vapor retarders or moisture control products are compatible with the wall assembly.
Practical Tips For Homeowners
- Follow Manufacturer Guidelines: Always use materials as intended by the manufacturer and within code requirements.
- Prioritize Local Code Compliance: Codes vary by state and municipality; ensure chosen products meet local standards for walls.
- Plan For Moisture Management: Include a drainage plane and vented rainscreen where possible to extend wall life.
- Budget For Proper Materials: While roofing felt may seem economical upfront, a proper WRB can prevent costly water damage and energy losses later.
- Consult Professionals: For renovations or unfamiliar builds, seek a licensed contractor or building professional to confirm suitable materials and installation methods.
Frequently Asked Questions
- Is roofing felt waterproof enough for walls? Not for long-term exterior use; it is designed as an underlayment for roofs and may deteriorate when exposed to wall conditions.
- Can I layer roofing felt behind siding? Some retrofits use barrier layers, but this should align with code-approved WRBs and not rely on felt as the primary barrier.
- What is a better alternative to roofing felt on walls? A certified weather barrier or rainscreen system designed for walls.
Conclusion
Roofing felt should not be used as a primary or durable wall barrier in U.S. construction. While it offers moisture resistance, it is not engineered for wall performance, weather exposure, or long-term durability. For exterior walls, rely on code-approved weather barriers, ventilation, and cladding systems that provide reliable protection and energy efficiency. For interiors, use appropriate wall assemblies and moisture controls. When in doubt, consult a licensed professional to select materials that meet local codes and ensure a safe, durable, and efficient wall system.