Tar paper, also known as roofing felt, is sometimes placed between subfloor layers to act as a moisture barrier, reduce squeaking, and provide a stable base for finish flooring. This guide explains when and how tar paper can be used between subfloors, its benefits and drawbacks, and best practices for modern construction and renovations in American homes. It also covers alternatives and common installation pitfalls to help readers make informed decisions.
What Tar Paper Is And Why It’s Considered For Subfloors
Tar paper is a tar- or asphalt-saturated felt sheet traditionally used in roofing and flooring applications. When installed between subfloors, tar paper can reduce friction, provide a minor vapor barrier, and help mitigate minor acoustic issues. The material is generally inexpensive, readily available, and easy to cut to size. However, it is not a primary moisture-control system in modern buildings, where code-compliant vapor retarders and proper subfloor assemblies are favored. Understanding its role helps homeowners assess whether it fits a specific project.
When To Consider Tar Paper Between Subfloors
Tar paper between subfloor layers may be considered in these scenarios:
- Renovations where a thin layer is needed to dampen squeaks or bridge irregularities between plywood sheets.
- Older homes with uneven subfloors where an additional layer of protection is desirable before installing finish flooring.
- Projects aiming to reduce nail pops and echo in rooms with hardwood or laminate floors.
It is important to note that tar paper should not be relied upon as the primary moisture barrier in areas prone to high humidity, standing water, or significant groundwater exposure. In such cases, modern vapor barriers and properly installed subfloor assemblies are preferred.
Benefits Of Using Tar Paper Between Subfloors
- Cost-Effective: Tar paper is inexpensive compared to other moisture-control products.
- Friction Reduction: The sheet can help prevent fastener back-out and reduce squeaks when mats or finish flooring are installed.
- Smoothing Minor Imperfections: It can fill minor gaps between subfloor panels, creating a more uniform surface for the finish floor.
- Ease Of Installation: The material is flexible, easy to cut, and compatible with many subfloor materials.
Drawbacks And Limitations
- Limited Moisture Protection: Tar paper is not a primary moisture barrier in modern flooring assemblies and may degrade under moisture exposure.
- Potential For Mold If Trapped: If moisture penetrates the finish floor, tar paper can trap it against the subfloor, increasing mold risk.
- Compatibility Issues: Some flooring products and adhesives perform better without tar paper, and some manufacturers discourage its use.
- Does Not Replace Proper Subfloor Venting: Adequate ventilation and proper vapor retarders remain essential in basements and crawlspaces.
Best Practices For Installing Tar Paper Between Subfloors
When choosing to use tar paper, follow these practice guidelines to maximize performance and minimize risk:
- Check Local Codes: Verify that tar paper usage between subfloors complies with local building codes and manufacturer recommendations for finish flooring.
- Use The Right Type: Choose a high-quality asphalt- or tar-saturated felt designed for interior use, with appropriate thickness for the project.
- Surface Preparation: Ensure subfloor surfaces are clean, dry, and free of protruding nails or debris before laying tar paper.
- Overlap And Fastening: Overlap sheets by at least 4 inches and secure with a compatible adhesive or staples as recommended by the product instructions. Do not over-tension.
- Seam Alignment: Align seams to minimize trip hazards and ensure a smooth finish surface for the finished flooring.
- Compatibility With Finish Flooring: Confirm that the finish flooring manufacturer’s installation guidelines permit tar paper between subfloors and that the adhesive and fasteners will perform properly over tar paper.
- Moisture Management: In damp or poorly ventilated spaces, complement tar paper with proper subfloor insulation and a dedicated moisture barrier where required by code.
Alternatives To Tar Paper Between Subfloors
Several modern alternatives may offer superior moisture control and performance based on the project needs:
- Vapor Barriers: Polyethylene or other vapor retarders installed on the appropriate side of the subfloor assembly provide a more reliable moisture barrier in many homes.
- Rigid Foam Underlayment: Polyiso or XPS underlayment can provide insulation, sound dampening, and moisture resistance, often meeting manufacturer guidance for various finish floors.
- Acoustic Underlayment: Specialized underlayments reduce impact noise and provide a smoother surface for wood, laminate, or vinyl flooring.
Common Installation Mistakes To Avoid
- Using Tar Paper As A Primary Barrier: Do not substitute tar paper for a proper moisture-control system in moisture-prone areas.
- Inadequate Coverage: Skipping overlaps or failing to seal seams can create weak points for moisture intrusion.
- Ignoring Manufacturer Guidelines: Some floorings require specific underlayment or may prohibit tar paper entirely.
- Overlooking Ventilation: Poor attic, basement, or crawlspace ventilation can negate moisture-control efforts regardless of underlayment.
Maintenance And Inspection
Routine checkups help ensure the subfloor assembly remains sound. Look for signs of moisture damage, warped or stained subfloor panels, and odors indicating mold or mildew. In basements and crawlspaces, install or maintain adequate ventilation and drainage to minimize humidity levels. If any moisture issues are detected, reassess the subfloor assembly and consider replacing tar paper with a more robust moisture-control solution per current building standards.
Frequently Asked Questions
- Is tar paper still needed between subfloors? In most new constructions, tar paper is not required and may be discouraged. It is more common in certain renovations where avoidance of squeaks or minor leveling is desired, but always follow manufacturer guidance.
- Will tar paper protect against moisture? It provides limited moisture control and should not replace a dedicated moisture barrier in high-moisture environments.
- Can tar paper cause mold? If moisture is present, tar paper can trap it against the subfloor, increasing mold risk; ensure proper moisture management.
Tar paper between subfloor layers is a niche practice with specific use cases. For most American homes, a modern subfloor assembly with appropriate moisture barriers, sound-dampening underlayment, and adherence to manufacturer guidelines offers superior performance. When considered thoughtfully, tar paper can be one tool in the broader strategy to achieve a smooth, durable floor finish with acceptable moisture control.