Can You Use Roofing Felt on Walls

Roofing felt is widely known as a water-resistant underlayment for roofs, but questions arise about its suitability for vertical applications. This article explores practical uses, limitations, installation tips, and better alternatives for using roofing felt on walls, helping readers make informed decisions for exterior and interior projects.

Use Case	Feasibility	Notes
Temporary Weather Barrier	Good	Short-Term Protection during construction; not UV-stable long term
Permanent Exterior Sheathing	Poor	Degrades from UV and not breathable if asphalt-saturated
Interior Vapor Barrier	Limited	May trap moisture; choose based on climate zone
Under Cladding (e.g., siding)	Conditional	Better options: house wrap or building paper with proper installation

What Is Roofing Felt And How It Works

Roofing felt, also called tar paper, is a sheet material made from paper or fiberglass mat saturated with asphalt and sometimes coated with mineral granules. It performs as a temporary waterproofing layer on roofs and helps shed incidental water. Its composition prioritizes water resistance and secondary protection, not long-term vertical exposure.

Common Types Of Roofing Felt And Their Properties

There are several types of roofing felt with different weights and constructions: 15-pound and 30-pound felt (organic or fiberglass), synthetic felts, and asphalt-saturated building papers. Synthetic felts are lighter, more tear-resistant, and less prone to degradation than traditional asphalt-saturated felt.

Asphalt-Saturated Felt

Asphalt-saturated felt has good short-term water resistance but is prone to tearing and UV damage. It can also become stiff in cold temperatures and brittle with age.

Synthetic Roofing Underlayments

Synthetic underlayments are engineered polymers that offer improved tensile strength, UV resistance, and lighter handling. They are better candidates for atypical uses than organic felt.

Can Roofing Felt Be Used On Exterior Walls?

Roofing felt can be used on exterior walls only in specific, controlled situations. It is commonly used as a temporary weather barrier during construction but is not recommended as a permanent wall moisture barrier. The primary reasons are UV degradation, limited breathability, and lack of engineered performance compared to modern solutions.

Temporary Weather Barrier

Contractors often drape roofing felt over sheathing as a quick temporary shield against rain. In this role, its water-shedding ability provides immediate protection before siding or proper house wrap is installed.

Permanent Installation Concerns

Long-term exposure to sunlight will break down asphalt-saturated felt, leading to crumbling or bleeding. Additionally, roofing felt is less vapor-permeable than many modern building papers, which may trap moisture and increase rot risk in wall assemblies.

Can Roofing Felt Be Used On Interior Walls?

Using roofing felt on interior walls is generally discouraged. Its asphalt content can off-gas and it is not designed as an interior vapor control layer. In some retrofit scenarios, builders used felt as a vapor barrier, but modern code and best practices favor purpose-made vapor retarders or smart membranes selected for the local climate.

Comparison: Roofing Felt Versus House Wrap And Building Paper

Comparing roofing felt to house wrap and building paper clarifies why alternatives often perform better on walls. House wrap (e.g., Tyvek) offers high moisture vapor permeability and excellent water resistance with UV tolerance. Building paper (e.g., asphalt-impregnated kraft) is breathable and designed for vertical use.

Material	Water Resistance	Breathability	UV Longevity
Roofing Felt	Good Short-Term	Low	Poor
House Wrap (Synthetic)	Excellent	High	Good
Building Paper (15#)	Moderate	Moderate	Fair

When It Is Acceptable To Use Roofing Felt On Walls

There are a few acceptable scenarios for using roofing felt on walls: temporary construction protection, emergency repairs, or where local codes permit and expected exposure is minimal. Use roofing felt only as a stopgap, not as a long-term wall assembly component.

Temporary Jobsite Protection

When siding installation will follow shortly, roofing felt can keep the structure dry during short delays. Secure felt properly to prevent wind damage and remove it before prolonged sun exposure.

Back-Up Layer Under Cladding

In rare retrofit or budget-limited cases, asphalt-saturated felt is sometimes accepted as a secondary layer under specific cladding systems. Always check local code and manufacturer requirements first.

Installation Best Practices If Using Roofing Felt On Walls

If roofing felt must be used on walls temporarily, follow proper installation to limit damage: overlap seams, fasten securely, protect from UV, and avoid trapping moisture. Proper flashing and drainage planes remain critical to prevent water intrusion.

• Install felt horizontally with upper course overlapping lower by at least 2 inches.
• Use corrosion-resistant staples or cap nails spaced per manufacturer guidelines.
• Protect exposed felt from direct sunlight by installing cladding within a short timeframe.
• Ensure flashing at windows, doors, and rooflines creates a continuous drainage plane.

Better Alternatives For Walls

For a durable wall moisture barrier, choose purpose-built materials: house wrap, felt-type building paper designed for walls, or fluid-applied membranes. These alternatives provide better breathability, UV resistance, and compatibility with modern wall assemblies.

House Wraps

House wraps are the modern standard for weather-resistive barriers; they provide high vapor permeability, reduce air infiltration, and are UV-resistant for reasonable exposure periods.

Felt-Type Building Paper

Building paper labeled for vertical use (e.g., 15-pound building paper) is formulated for walls and balances water resistance with breathability to minimize trapped moisture.

Fluid-Applied Membranes

Liquid-applied membranes form a continuous, seamless barrier and are ideal where complex flashing is needed. They adhere directly to sheathing and are highly durable.

Code, Warranty, And Manufacturer Considerations

Always consult local building codes, siding manufacturers, and warranty conditions before installing any product. Using roofing felt in ways not intended by the manufacturer can void warranties and fail inspections.

Practical Examples And Case Studies

Examples from field practice show roofing felt used as a temporary barrier on residential remodels; where it remained exposed due to delays, UV damage and accelerated degradation occurred. Conversely, projects that switched to synthetic house wrap experienced fewer air and moisture problems and smoother siding installation.

Key Takeaways For Contractors And Homeowners

Roofing felt can serve as a temporary, short-term weather barrier on walls but is not a recommended long-term solution. Choose materials designed for vertical use—house wrap, building paper, or fluid membranes—for durable, code-compliant wall assemblies.

Practical Checklist Before Using Roofing Felt On Walls

• Confirm duration of exposure will be minimal.
• Verify local building code acceptance.
• Plan for prompt cladding installation to limit UV damage.
• Provide proper flashing and drainage details.
• Consider synthetic alternatives if longer exposure or added durability is needed.

For any specific project, consulting a licensed contractor or building inspector will ensure compliance and long-term performance when choosing between roofing felt and dedicated wall barrier materials.