Tar paper, commonly referred to as roofing felt or asphalt-impregnated felt, is a versatile building material used to provide a protective barrier in roofing, walls, and foundations. It combines a base paper with asphalt or bitumen coatings that offer water resistance, lubricity, and durability. This material has evolved over decades, adapting to modern building codes and environmental considerations. Understanding tar paper’s purpose, composition, and installation helps homeowners, builders, and inspectors assess its suitability for specific projects and climates.
What Tar Paper Is
Tar paper is a heavy, flexible sheet made from a base substrate—traditionally organic felt such as cellulose or fiberglass—saturated with asphalt or bitumen. The coating creates a waterproof layer that resists moisture ingress. The sheets are usually sold in rolls with widths ranging from 36 to 54 inches and thicknesses that vary by grade. Tar paper serves as a weather-resistant underlayment under shingles or other exterior finishes, shielding roof decks from wind-driven rain and snow.
Key takeaway: Tar paper is a moisture barrier that supports other roofing materials by reducing water penetration at vulnerable seams and fastener points.
Composition And Types
The base substrate can be organic felt or fiberglass, each with distinct properties. Organic felt offers good tear resistance but is more susceptible to moisture over time. Fiberglass-based tar paper provides improved fire resistance and dimensional stability. The asphalt coating seals the layer, but different grades exist for weather exposure duration and climate conditions.
Common types include:
- Standard Roofing Felt: Basic underlayment used under shingles with moderate exposure protection.
- 35 Lbs And 40 Lbs: Designations indicating weight per 100 square feet, reflecting durability and tear resistance.
- Synthetic Underlayment: Modern alternatives using non-paper substrates with superior water resistance and longevity, often used in harsh climates.
- Self-Adhering Tar Paper: Pressure-sensitive asphalt strips or adhesives add tack to improve wind resistance and installation speed.
Note: Builders increasingly favor synthetic underlayments for longevity, but traditional tar paper remains common for cost-effective, proven performance in many projects.
Uses In Construction
Tar paper is primarily used as an underlayment in roofing to create a secondary barrier against moisture that seeps through roof coverings. It also serves in wall assemblies as a moisture spacer and air barrier in some retrofits and renovations. In foundations, tar paper’s waterproofing properties can be leveraged in early-stage damp-proofing systems when paired with other barrier materials.
Typical applications include:
- Underlayment beneath asphalt shingles, metal roofing, or tile to guard against leaks at joints and rafter connections.
- Temporary weather barrier during construction to protect the interior while final finishes are completed.
- Moisture mitigation in basements or crawl spaces when used with proper drainage and vapor barriers.
Benefits And Limitations
Benefits of tar paper include cost-effectiveness, ease of installation, and an additional moisture barrier that helps extend roof life. It provides a workable surface for fastening roof materials, reduces wind-driven leaks at edge constructions, and is compatible with a wide range of climates when matched with the right grade.
Limitations involve aging and deterioration under prolonged exposure to UV light and heat, potential wrinkling, and reduced performance in extreme weather without proper overlap and fastening. In some climates, synthetic underlayments or peel-and-stick membranes offer longer service lives and lower maintenance needs.
Choosing The Right Tar Paper
Selecting the appropriate tar paper depends on climate, roof type, and local building codes. Consider the following:
- Exposure Rating: Choose a grade that accommodates the expected roof exposure and wind loads.
- Base Material: Fiberglass provides better moisture and heat resistance; organic felt is affordable but less durable when exposed to moisture.
- Adhesive Options: Self-adhering varieties reduce installation labor and improve wind uplift resistance.
- Compatibility: Ensure compatibility with the chosen roofing material and installed ventilation and drainage systems.
Always verify current local codes and manufacturer specifications to ensure proper installation guidelines are followed and to determine whether a synthetic alternative might offer superior performance.
Installation Best Practices
Proper installation maximizes tar paper effectiveness and roof longevity. Key steps include:
- Preparation: Clean the deck, remove protruding nails, and ensure a dry surface before application.
- Overlap And Sealing: Maintain consistent overlaps (typically 19 to 19 inches in roofing applications) and seal edges with approved fasteners or adhesives to prevent wind uplift.
- Fastening: Use the correct nails or staples for the substrate and climate, following manufacturer guidelines for spacing and penetration.
- Ventilation And Drainage: Integrate with roof ventilation and ensure proper drainage to reduce moisture buildup behind the underlayment.
- Weather Conditions: Avoid installing tar paper in freezing temperatures or when rain is imminent to prevent adhesive failure and moisture entrapment.
For DIY projects, many homeowners opt for self-adhering or simpler roll options, while complex or high-wind regions may require professional installation to meet code requirements.
Common Misconceptions
Several myths surround tar paper. These include the belief that tar paper alone waterproofs a roof or that it is unnecessary with modern shingles. In reality, tar paper is a secondary moisture barrier and must be used with a properly installed roofing system. Another misconception is that all tar papers are equal; discrepancies in base material, weight, and adhesive technology lead to varied performance. Understanding product data sheets helps separate fact from folklore.
Safety And Environmental Considerations
Tar paper contains asphalt, which carries fumes during manufacturing and installation. Adequate ventilation and personal protective equipment (PPE) reduce exposure risks. When decommissioning or removing tar paper, proper disposal is essential, and some products may be recycled or repurposed. For environmentally conscious projects, consider modern synthetic underlayment options that offer lighter weight, higher tear resistance, and longer lifespans while still meeting performance standards.
Maintenance, Longevity, And Inspection
Tar paper’s lifespan is influenced by exposure, climate, and roof maintenance. Regular inspections after major weather events can catch tears, punctures, or degraded edges early. Signs of failure include loose edges, wrinkles, blistering, or visible water stains on interior ceilings. In many installations, tar paper will last 15 to 30 years, though extreme heat, direct sun, or poor ventilation can shorten service life. Replacement or repair should be considered when damage is extensive or compromised by underlying deck issues.
Cost Considerations
Tar paper remains a cost-effective underlayment option, with price influenced by base material (organic felt vs. fiberglass), weight, and whether an adhesive layer is included. Self-adhering versions add material costs but can reduce labor expenses and improve wind resistance. When budgeting, factor in installation complexity, local climate, and compatibility with chosen roofing materials to ensure a durable, code-compliant system.
Common Questions
Is tar paper still necessary with modern roofing? Yes, as a secondary moisture barrier, though some builders opt for high-end synthetic underlayments that provide enhanced properties and longevity.
Can tar paper be used on walls? It is primarily a roofing underlayment, but in some wall assemblies, it can serve as a moisture barrier when combined with other materials.
How long does tar paper last? Depending on climate and exposure, 15 to 30 years is common, with synthetic underlayments sometimes exceeding that lifespan.