Can You Use Roofing Felt on Walls

Roofing felt, often referred to as tar paper or bitumen felt, is traditionally used as a weatherproofing layer on roofs. Some builders and DIYers wonder if it can serve on walls as a weather barrier or creative siding. This article explains what roofing felt is, how it behaves when applied to walls, practical applications, installation considerations, and viable alternatives. It covers the practical, safety, and code implications to help homeowners and builders decide whether roofing felt on walls is appropriate for a given project.

What Is Roofing Felt And How It Works

Roofing felt is a coarse paper or fiberglass mat coated with asphalt or bitumen to create a moisture barrier. On roofs, it acts as a secondary defense against moisture intrusion before shingles or other coverings are applied. On walls, roofing felt can serve as a drainage plane or simple air barrier in some low-cost or temporary builds. The material’s permeability, durability, and UV resistance vary by product type, including traditional tar paper and modern synthetic felts. When used on walls, the lack of proper detailing at penetrations and joints can lead to leaks if not installed correctly.

Historical And Modern Uses Of Roofing Felt On Walls

Historically, tar paper walls appeared in temporary or low-cost structures where quick weatherproofing was prioritized over long-term performance. In some rural or emergency-build settings, felt was used under siding or as a ventilated cavity barrier. Modern construction has largely moved toward more advanced wall assemblies that provide continuous air barriers and proper drainage. Some builders still use roofing felt as a temporary weatherproofing layer behind siding, but this is not the typical finish and is rarely a primary weather barrier in modern codes.

Pros And Cons Of Using Roofing Felt On Walls

• Pros: Inexpensive material, familiar installation methods, provides a basic moisture barrier behind siding, can protect against wind-driven rain during installation, flattens in humid conditions to reduce drafts when used correctly.
• Cons: Not designed as a long-term wall weather barrier, limited UV resistance, potential for abrasion and tearing, poor compatibility with many siding systems, can trap moisture if not properly vented, may void certain codes or warranty terms if used as a primary barrier.

Suitable Applications And Limitations

Roofing felt can be considered in specific scenarios, such as a temporary weatherproofing layer during construction or renovation where the wall assembly will later receive a dedicated air barrier and proper exterior finish. However, it should not be treated as the primary moisture barrier in a typical exterior wall system. For interior applications, felt is generally not recommended as a finish layer on walls due to its texture, risk of tearing, and moisture trapping potential behind finishes like drywall. For any wall in a humid climate, relying on roofing felt as a moisture barrier can lead to mold, wood rot, and reduced insulation effectiveness.

Installation Tips For Walls

If a project calls for roofing felt on walls as a temporary measure, follow careful steps to minimize risk. Use weather-rated and UV-stable products designed for prolonged exposure if possible. Install on clean, dry surfaces and overlap seams at least 4 to 6 inches with weather-resistant tape or fasteners approved for external use. Avoid overlapping too tightly near windows, doors, and penetrations, which can trap moisture. Seal all joints and ensure proper drainage behind the siding by maintaining gaps or a ventilation space as required by the siding system. Do not rely on felt as a substitute for a continuous air barrier or vapor control layer.

Code And Moisture Considerations

Building codes in the United States typically require a continuous weather-resistive barrier (WRB) on exterior walls, such as house wrap or a compatible weather barrier system, with a vented or moisture-managed exterior finish. Roofing felt is rarely specified as the primary WRB in modern codes. When used, it should be part of a broader wall assembly that includes a proper drainage plane, air barrier, vapor control, and cladding. In high moisture climates, improper use of roofing felt can lead to condensation, microbial growth, and structural damage. Always verify local code requirements and manufacturer installation instructions for any wall system.

Alternative Options For Wall Weatherproofing

Several alternatives provide better performance and durability than roofing felt when used on walls. Consider these approaches:

• House Wrap Or Air-Barrier Systems: Modern house wraps or taped air barriers provide superior moisture control and are designed to work with claddings and rain screens.
• Ventilated Rain Screens: A drainage plane with a vented siding creates an air gap that helps manage moisture and improve efficiency.
• Liquid-Applied Membranes: Flexible, seamless coatings that form a continuous barrier on exterior walls, often used in combination with tapes and flashings.
• Closed-Cell Foam Or Rigid Board Backups: In certain designs, foam boards with a proper WRB behind the siding can improve insulation and moisture management.
• Proper Drainage Planes: Siding systems with clear drainage paths reduce water intrusion and extend wall life.

Recommendations For Homeowners

For most modern residential projects, avoid using roofing felt as the primary wall weather barrier. If a temporary or budget-driven scenario requires roofing felt, treat it as a short-term measure and ensure a compliant WRB, proper drainage, and a suitable exterior finish are installed as soon as possible. When planning renovations, consult a professional to design a wall assembly that meets current codes and local climate demands. Prioritize drainage, ventilation, and a continuous barrier to minimize moisture-related risks.