Yes, roofing felt can be used on walls as a water-resistive barrier, but it is not automatically a substitute for modern housewrap or a complete wall-weatherproofing system. The right choice depends on the product, local building code, wall design, and how the layers are installed. Roofing felt may work beneath siding in some applications, while incorrect placement or detailing can trap moisture and contribute to rot. Understanding what felt does—and what it does not do—helps homeowners choose a suitable product and avoid costly moisture problems.
What Roofing Felt Does on a Wall
Roofing felt, also called asphalt-saturated felt or underlayment, is a sheet material traditionally installed beneath roof shingles. Some types are also used behind exterior wall cladding. When installed over wall sheathing and beneath siding, felt can serve as a water-resistive barrier (WRB): a layer intended to limit water that gets behind the siding and direct it back outside.
A WRB is not the same as siding, flashing, or a waterproof membrane. Siding sheds most rain, but wind-driven water can pass through joints and openings. The WRB provides a secondary drainage plane behind the cladding. Flashing around windows, doors, roof-wall intersections, and other openings connects to that plane so water can drain outward.
Roofing felt also should not be confused with a vapor barrier. A vapor retarder slows water vapor moving through a wall; a WRB manages bulk liquid water. Some materials can perform more than one function, but the functions and requirements are distinct. A wall assembly needs to manage both rainwater and water vapor without trapping moisture.
Is Roofing Felt Allowed on Walls?
In many U.S. residential applications, asphalt-saturated felt can qualify as a WRB when it meets applicable standards and is installed according to the building code and product instructions. The International Residential Code (IRC) includes provisions for water-resistive barriers, including certain asphalt felts that comply with referenced material standards. Local jurisdictions may adopt different code editions or amendments, so acceptance should be checked with the local building department.
Code compliance is not a blanket approval for every product labeled “roofing felt.” Roofing underlayment products vary, and some are designed specifically for roofs rather than walls. A synthetic roof underlayment, for example, should not be assumed suitable as a wall WRB just because it is water-resistant. The manufacturer’s technical documentation should expressly identify the product’s approved use and installation details.
For a project requiring a permit, the plans, code official, or product evaluation report may specify the acceptable WRB. In some areas, requirements may also address wind resistance, fire performance, drainage, or installation over particular sheathing. When the code or product instructions are unclear, verify them before covering the wall.
Roofing Felt Versus Housewrap
Housewrap is a broad category of sheet WRBs, commonly made from spun-bonded or woven synthetic materials. Roofing felt is generally asphalt-saturated paper or another felt-based product. Both can be used as part of a wall assembly when suitable for that application, but their handling, water resistance, vapor characteristics, and installation requirements differ by product.
| Feature | Roofing Felt | Housewrap |
|---|---|---|
| Common use | Roof underlayment; some approved products are used on walls | Exterior wall WRB beneath cladding |
| Material | Typically asphalt-saturated felt or a related product | Usually a synthetic sheet material |
| Water management | Can shed water when correctly lapped and detailed | Designed to shed water when correctly installed and integrated with flashing |
| Air control | Generally not a complete air barrier by itself | Some products can contribute to air control when seams and penetrations are sealed as specified |
| Installation | Can be more prone to tearing or wrinkling; product directions govern | Often available in wider rolls with system-specific tapes and accessories |
| Compatibility | Check compatibility with cladding, coatings, and adhesives | Check compatibility with tapes, sealants, and cladding systems |
Neither material is automatically better in every project. Felt can be a practical option where a specific product is approved and the installer can detail it correctly. Housewrap may be easier to handle or integrate with accessories, depending on the product. The most important factors are code acceptance, product instructions, drainage, flashing, and compatibility with the rest of the wall assembly.
When Roofing Felt May Be Appropriate
Roofing felt may be appropriate behind certain types of exterior siding when the felt is rated or accepted for wall use and the wall is designed to drain and dry. It is commonly considered in traditional construction or repairs where the existing assembly already uses felt. It may also be specified by a designer or manufacturer for a particular cladding system.
Whether it is appropriate depends on the full assembly, not simply on the felt. Wood, fiber-cement, vinyl, and masonry veneer siding have different attachment and drainage details. Some claddings require a drainage gap, rainscreen, or specialized membrane. Stucco and manufactured stone veneer, for example, can have their own code and manufacturer requirements; a single layer of felt should not be assumed to meet them.
Felt is also not a substitute for fixing existing water damage. If sheathing is rotten, flashing is missing, or siding is allowing persistent leaks, covering the wall with a new layer can conceal the underlying problem. The source of water should be corrected, and damaged materials evaluated before the assembly is closed.
How to Install Roofing Felt on Walls
Installation details vary by product and wall design. The following steps describe general principles, not a replacement for the manufacturer’s instructions or local code requirements.
- Confirm suitability. Check the product label and technical data for wall use, applicable standards, fastening guidance, and compatibility with the cladding.
- Prepare the surface. Install over sound, properly supported sheathing or the substrate specified for the product. Remove protruding nails and address damaged areas before covering them.
- Plan drainage from the top down. Install lower courses first, then overlap upper courses over them so water runs outward and down rather than behind the barrier. Follow the required horizontal and vertical lap dimensions.
- Use suitable fasteners. Fastener type, spacing, and placement should follow the instructions and account for wind exposure. Avoid unnecessary holes or damage.
- Integrate flashing. Window and door flashing, sill pans, kick-out flashing, and other transitions must connect with the WRB in a shingle-fashion sequence. The WRB alone cannot compensate for poorly detailed openings.
- Seal or treat seams only as specified. Some felt installations rely on overlapping layers; others may require particular tapes or accessory materials. Do not assume that ordinary tape or sealant is compatible.
- Install cladding promptly and correctly. Protect exposed felt from prolonged weather and install the siding, furring, or drainage components required by the wall design.
At openings, the sequence matters: water should move from the upper WRB onto head flashing, while sill details should direct water outward. Details vary among window types and manufacturers. Following a generic diagram without checking the actual window and WRB instructions can create a leak path.
Important Moisture and Ventilation Considerations
A wall must be able to manage water and dry. If rain enters behind siding, the WRB should guide it out; if moisture is trapped between low-permeance layers, the wall may dry slowly. The risk depends on climate, indoor humidity, insulation, exterior sheathing, cladding, and the location and type of vapor-retarding materials.
Roofing felt’s vapor permeance varies with product type and conditions. It should not be treated as a universal vapor-control solution. Placing felt on the interior side of a wall, or adding it over an existing wall without evaluating the assembly, can create moisture problems. In cold climates, warm indoor air leaking into cold parts of a wall can condense; in hot-humid climates, air-conditioning and vapor drive can create different risks.
Where a wall includes foam insulation, foil-faced materials, interior polyethylene, or other low-permeance layers, a qualified building professional may need to assess the assembly. This is especially important in mixed or extreme climates, in older buildings, and when replacing siding on walls that have a history of leaks.
Common Mistakes to Avoid
- Using any roof underlayment on a wall. Products designed for roof decks may not be approved or durable as wall WRBs.
- Installing laps in the wrong direction. Reverse laps can funnel water behind the felt instead of draining it outward.
- Ignoring windows and penetrations. Unflashed openings, pipes, vents, and electrical boxes are common leak points.
- Leaving felt exposed too long. UV exposure, wind, and weather can degrade some products; follow the stated exposure limit.
- Assuming felt is waterproof. It is part of a drainage system, not a substitute for properly installed siding, flashing, and transitions.
- Covering deteriorated sheathing. Concealing rot or active leaks can make repairs more extensive later.
- Mixing incompatible materials. Adhesives, sealants, tapes, and cladding components should be approved for contact with the selected WRB.
How to Choose the Right Wall WRB
Before buying material, identify the siding type, wall substrate, climate, and project scope. Review the local code requirements and the cladding manufacturer’s installation guide. Then compare WRB products by approved use, water-resistance performance, vapor permeance, air-barrier claims, exposure limits, and available flashing accessories.
For an uncomplicated repair, a matching product or detail may be appropriate, but older walls can hide multiple layers and unusual materials. For a whole-house re-side, new construction, stucco, masonry veneer, or a wall with recurring moisture, professional design or inspection can help prevent failures. A contractor should explain how water is directed around openings and drained at the base of the wall—not merely name the sheet material.
Reliable Sources and Further Guidance
For code details, consult the locally adopted residential building code and the local building department. The International Code Council’s code resources provide access to model-code information, while the applicable local edition determines what is enforceable in a specific location.
The U.S. Department of Energy explains how air leakage affects home performance, and the Building Science Corporation publishes technical guidance on water management, vapor control, and durable wall assemblies. Product manufacturers’ current installation instructions remain essential because requirements differ by material and system.
The Practical Answer
Roofing felt can be used on walls when the specific product is suitable, code-compliant, and installed as part of a correctly detailed drainage system. It is not a universal replacement for housewrap, flashing, or a vapor-control strategy. Check local requirements, follow the product instructions, and make sure every opening and transition directs water to the exterior. Those details determine whether the wall stays dry far more than the name of the sheet material alone.