Roofing felt, commonly used as an underlayment on roof decks, is sometimes considered for flooring projects to save money. This article explains why roofing felt is generally not suitable as a floor underlayment, outlines potential risks, and compares safer, code-approved alternatives for common U.S. floor coverings. It covers moisture control, subfloor preparation, and installation considerations to help homeowners and builders make informed decisions.
Is Roofing Felt Suitable For Floor Underlayment?
Roofing felt is designed for roofs, not interior subfloors. It is thin, flexible, and can buckle or tear under foot traffic, making it an unstable base for most floor coverings. When used as floor underlayment, asphalt-saturated felt often fails to deliver a flat, uniform surface. In addition, the asphalt content can interact with certain adhesives and finishes, potentially causing staining, adhesive breakdown, or odor issues. Because of these factors, most manufacturers and building codes do not approve roofing felt as a primary floor underlayment.
- Not a structural buffer: It does not provide the stiffness needed to prevent deflection or squeaks in wood subfloors.
- Limited moisture control: It is not rated as a continuous vapor barrier for floors and moisture can become trapped beneath the finish.
- Compatibility concerns: Many floor finishes require a smooth, uniform substrate; roofing felt can create ridges, dimples, and alignment problems.
In sum, roofing felt is typically considered a misfit for reliable floor underlayment in most residential applications. If a project requires significant moisture resistance, sound control, or a smooth surface, safer, code-approved options should be chosen.
How Roofing Felt Behaves Under Floor Coverings
Underlayment plays a critical role in performance, comfort, and longevity of the finished floor. Roofing felt’s properties can lead to several issues when used beneath floor coverings. It may compress or shift under movement, causing unevenness, cracking in tiles, or squeaks in wood floors. Its surface can remain irregular after installation, transferring imperfections to the top layer. The material also lacks uniform thickness, which complicates achieving consistent transitions between rooms. Finally, its adhesive compatibility is variable, potentially compromising the bond of vinyl, laminate, or wood finishes.
Even if a thin layer seems tolerable at first, long-term use often reveals hidden problems as humidity, temperature changes, and foot traffic take their toll. Homeowners should weigh these risks against any perceived savings and consider how a failure would affect the room’s function and aesthetics.
Safer Alternatives For Common Floor Types
Engineered Wood Or Hardwood Floors
For engineered wood or solid hardwood, use a purpose-built underlayment designed for wood floors. Common options include rosin paper (or similar paper underlayments) and foam or cork underlayments that provide a smooth, even surface. A dedicated underlayment also helps manage minor substrate irregularities and improves sound and comfort without compromising finish adhesion. Always follow the flooring manufacturer’s recommendations for underlayment types, thickness, and moisture suitability.
Before installation, ensure the subfloor is dry, clean, and flat. Any gaps or high spots should be addressed with leveling compounds or sanding. If a moisture barrier is required, apply the appropriate vapor barrier as specified by the underlayment and flooring manufacturer.
Laminate Or Vinyl Plank
Laminate and vinyl plank flooring typically rely on a thin but stable underlayment for sound control and minor leveling. Foam or cork underlayments with a built-in moisture barrier are common choices. For concrete slabs or high-moisture areas, a separate vapor barrier may be required. The key is a uniform surface that resists compression and movement, supporting a long-lasting, gap-free floor finish.
In many cases, a selected underlayment will also provide a favorable surface for click-lock or glue-down installation, depending on the product. Always verify compatibility with both the flooring and the substrate to prevent issues with warranty coverage.
Tile Or Natural Stone
Tile or natural stone floors on wood substrates require a rigid, crack-resistant underlayment such as cement backer board, fiber cement board, or an uncoupling membrane. These substrates provide a stable base for tile, reduce crack transfer, and accommodate expansion and contraction without mirror deterioration of the surface finish. Underlayment products designed specifically for tile enable better adhesion and long-term performance compared with roofing felt.
When tiling over a wooden subfloor, ensure there is proper subfloor stiffness, moisture control, and surface flatness. Use fast-setting thinsets and appropriate spacers, and follow the tile manufacturer’s guidelines for movement joints to prevent cracking.
Installation Considerations And Best Practices
If roofing felt is already present or the project constraints push toward cheaper substrates, consider these best practices to minimize risk. First, verify substrate dryness and flatness before any underlayment choice. Second, avoid stacking felt layers or relying on the felt to provide uninterrupted moisture protection. Third, choose a finish that tolerates minor substrate imperfections and follow manufacturers’ installation instructions for expansion gaps and transitions. Finally, document substrate choices and consult local building codes and product warranties to ensure compliance.
In most scenarios, replacing roofing felt with a purpose-made underlayment is the prudent approach. A proper underlayment improves durability, comfort, and the floor’s overall lifespan, while preserving warranties and performance expectations.
Moisture Management And Code Considerations
Moisture control is essential in any interior floor installation. Concrete slabs, subfloor plywood, and other substrates must meet the moisture limits set by the flooring or underlayment manufacturer. In basements or ground-level rooms, a continuous vapor barrier may be required to prevent moisture vapor from migrating to the finish. For wood subfloors, maintain appropriate humidity levels to minimize expansion and contraction, which can cause squeaks and finish defects. Local building codes and flooring manufacturers’ guidelines should always be consulted to ensure compliant, durable installations.
Before selecting underlayment, check for compatibility with the chosen flooring product, especially for adhesives, click-lock systems, and floating installations. In cases of uncertain moisture risk or subfloor history, a professional assessment can prevent costly failures after installation.
Comparative Underlayment Options
| Underlayment Type | Best For | Pros | Cons |
|---|---|---|---|
| Roofing Felt ( asphalt-saturated) | Rarely recommended for floors | Low cost; readily available | Not designed for floors; poor flatness; limited moisture control; may damage finishes |
| Rosin Paper / Kraft Paper | Wood subfloors with wood finishes | Improves glide and reduces squeak; inexpensive | Limited moisture barrier; not for concrete slabs |
| Foam Underlayment | Laminate and engineered wood | Excellent sound dampening; provides smooth surface | Can be damaged by moisture if not paired with a barrier |
| Cement Backer Board | Tile and stone on wood subfloors | Rigid, crack-resistant; excellent for adhesion | Heavy; requires cutting and mounting |
| Cork Underlayment | Flooring with good thermal and acoustic performance | Comfortable; natural material; moisture resistant in some variants | Can be more expensive; wear resistance varies |
Bottom line: Roofing felt should not be the default choice for floor underlayment. For most interior floors, select a dedicated underlayment designed for the specific floor finish, substrate, and moisture conditions. The right underlayment improves flatness, sound, comfort, and longevity while preserving warranties and performance.
Frequently Asked Questions
Can roofing felt be used under vinyl flooring?
Generally, roofing felt is not recommended under vinyl flooring due to potential dimensional instability, moisture issues, and compatibility challenges with adhesives. Use a manufacturer-approved underlayment for vinyl and follow installation instructions closely.
Is roofing felt ever acceptable for interior flooring projects?
In rare cases, some retrofits or temporary installations may use roofing felt as a quick, low-cost substrate, but this is not standard practice and is not advised for long-term installations. Always consult the flooring manufacturer and local building codes before proceeding.
What is the best practice for moisture control with wood subfloors?
Best practice includes testing moisture content in the subfloor, using a proper moisture barrier where required, and selecting underlayment with an appropriate vapor barrier rating. Follow both the flooring and underlayment manufacturers’ guidelines for optimal performance.