Roofing felt is a cost-effective material that some homeowners consider for wood floor underlayment. While it is traditionally used as a roofing moisture barrier, its availability and familiarity in construction can make it seem like a practical choice for underside protection and leveling beneath wood flooring. This article examines whether roofing felt is a suitable underlayment for wood floors, outlining benefits, drawbacks, installation steps, and safer alternatives that improve moisture control, sound transmission, and floor stability in American homes.
What Is Roofing Felt And Its Traditional Uses
Roofing felt is a flexible, paper- or fiberglass-backed sheet saturated with asphalt or bitumen. Its primary role is to act as a secondary weatherproofing layer beneath roof shingles, providing a moisture barrier and helping to shed water. In some building contexts, contractors repurpose roofing felt for concrete subfloors or wall assemblies. For wood floor underlayment, the material is used as a thin, inexpensive layer that sits between the structural floor and the finish flooring. Its characteristics—availability, ease of cutting, and compatibility with various joist configurations—drive interest but do not guarantee suitability for every wood floor project.
Pros Of Using Roofing Felt As Underlayment
Pros that often influence a homeowner’s choice include cost savings, ease of handling, and moisture mitigation advantages in certain scenarios. Low cost makes roofing felt appealing for temporary or budget-driven projects. It is easy to cut to fit irregular spaces around pipes or vents, reducing labor time. When used over a sealed, dry subfloor, felt can provide a minimal barrier against minor moisture vapor, especially in enclosed, climate-controlled spaces. Some installers appreciate the familiar substrate with compatible thickness for low-profile flooring. Additionally, roofing felt can act as a temporary solution during renovations before installing higher-performance underlayment.
Limitations exist alongside these benefits. Roofing felt lacks the engineered features found in modern underlayments, such as dedicated vapor barriers, acoustical damping, and dimension stability. It is crucial to ensure the underlying subfloor is dry and structurally sound; otherwise, the felt offers little protection against moisture or movement that can lead to squeaks and gaps.
Cons And Cautions
Using roofing felt as wood floor underlayment presents several concerns. Moisture control is not optimized in most roofing felts for interior humidity, especially in basements or crawl spaces where moisture migration is possible. Sound transmission is often not adequately mitigated; thin felt provides minimal impact on impact or airborne noise, potentially resulting in a louder floor. Dimensional stability is another issue; felt can compress and shift under load or temperature changes, leading to uneven surfaces or squeaks. In many wood floor installations, manufacturers require specific underlayment types with tested performance, which roofing felt may not meet. Additionally, some building codes or warranty terms may disallow roofing felt as a permanent underlayment due to its permeability and aging characteristics.
For concrete slabs, improper use of roofing felt may trap moisture against the slab or create a false sense of protection, compromising long-term flooring performance. When the home experiences high humidity fluctuations or seasonal moisture shifts, felt can delaminate or deteriorate faster than purpose-built underlayments. These factors collectively argue against routine use of roofing felt as an underlayment for wood floors in many American homes.
Installation Guidelines
If roofing felt is chosen as a temporary or experimental underlayment, follow careful steps to minimize risk. Inspection starts with a dry, clean subfloor free of debris, oil, or old adhesive residues. If the subfloor is concrete, test moisture with a reliable meter and ensure a stable surface before laying any felt. Preparation requires cutting the felt to fit, leaving narrow gaps at walls to allow for expansion. Align sheets along the direction of floor joists or as recommended by the flooring manufacturer. Sealing at edges with compatible tape can reduce draft and moisture intrusion, though this is not a substitute for a true moisture barrier. Fastening should be gentle to avoid tearing; avoid staples that protrude through the top surface. After installing flooring, check for obvious gaps or ridges and address them promptly to prevent squeaks or unevenness. It is essential to confirm compatibility with the final wood flooring product and to adhere to local building codes and warranty requirements.
When It Is Appropriate Or Not
Roofing felt may be considered in temporary or budget-limited renovations where a complete underlayment system is unavailable, or as a stopgap between major upgrades. It is generally not recommended for high-end or moisture-sensitive installations, where specialized underlayment products provide superior moisture management, sound attenuation, and long-term stability. For homes with basements or subfloor moisture issues, choosing proven moisture barriers, vapor retarders, or combinations of underlayment products designed for interior use is advisable. If roofing felt is used, it should be paired with other moisture-control strategies, such as proper subfloor preparation, controlled ventilation, and interior humidity management, to reduce risk. In new constructions and major renovations, opt for underlayment materials specifically designed for wood floors to maximize performance and warranty protection.
Alternatives To Roofing Felt
Modern underlayments deliver improved performance with less risk. Options include polypropylene or cork underlay for sound dampening and moisture control, polyethylene foam underlayment for impact absorption and thermal comfort, and cement-board-backed underlayment for durable, stable support under ceramic or stone finishes. For nail-down or floating floor systems, choose underlayments with manufacturer-approved moisture barriers and acoustic ratings. When moisture is a concern, consider a dedicated vapor barrier layer integrated into the underlayment assembly. Always verify compatibility with the chosen finish flooring and the building’s climate and moisture profile.