Building Paper vs Roofing Felt: Differences, Uses, and Installation
Building paper and roofing felt are common underlayment options in residential construction, serving different purposes in wall and roof assemblies. Understanding their properties, installation requirements, and code considerations helps builders choose the right material for durability, weather protection, and cost. This article compares building paper and roofing felt, clarifies where each fits best, and offers practical installation guidance for American construction projects.
What Is Building Paper?
Building paper, sometimes referred to as house wrap or building wrap, is a non-woven or woven sheet designed to provide an air barrier and moisture management. It is typically installed on exterior wall sheathing before siding to reduce air leakage and improve energy efficiency. Modern building papers often incorporate breathable membranes that allow water vapor to escape while blocking liquid water intrusion. Building paper is not intended to be used as a roof underlayment.
What Is Roofing Felt?
Roofing felt, also called tar paper or asphalt felt, is a saturated paper product used as an underlayment for roofing systems. It provides a temporary weather barrier during construction and serves as a secondary line of defense against water infiltration if shingles or tiles are damaged. Roofing felt comes in different weights, commonly #15, #30, or #40, indicating its thickness and tear resistance. It is specifically designed for roof decks and is not used as wall sheathing protection.
Key Differences
- Purpose: Building paper acts as a wall moisture and air barrier; roofing felt protects roof decks and provides temporary weatherproofing.
- Location: Building paper is installed on exterior walls; roofing felt is installed on roof sheathing.
- Breathability: Building paper often emphasizes vapor permeability; roofing felt focuses on shedding water and resisting tearing.
- Durability: Roofing felt is designed to withstand foot traffic and weather exposure during roofing; building paper is chosen for long-term wall performance.
- Code Roles: Building paper supports continuous insulation and air barrier strategies; roofing felt aligns with roofing underlayment requirements and wind-driven rain considerations.
Applications And Compatibility
In wall assemblies, building paper improves energy efficiency by reducing drafts and controlling moisture movement. It pairs with moisture barriers and exterior cladding to create a continuous enclosure. Roofing felt is standard in many roofing systems, especially in areas requiring an additional protective layer beneath shingles, tiles, or metal roofs. The choice depends on climate, roof design, and local building codes. In some cases, builders use a modern synthetic roof underlayment instead of traditional felt for improved durability and easier installation.
Installation Guidelines
Proper installation is essential for effectiveness. Building paper should be installed with overlapping and sealed seams to minimize air leakage. Siding fasteners should not compromise the barrier; gaps around windows and doors must be properly flashed. Roof underlayment installation requires proper nailing patterns, shingle overhang control, and adherence to manufacturer instructions. In cold climates, ensure materials remain pliable and guard against ice dam formation with appropriate flashing and insulation. Always follow local code requirements and manufacturer guidelines for both products.
Durability And Lifespan
The lifespan of building paper depends on exposure, climate, and exterior finish behind it. When properly installed with a durable cladding system, these membranes can contribute to long-term energy efficiency and moisture management. Roofing felt’s lifespan is influenced by weather exposure during construction and the roof covering installed over it. Conventional asphalt felt may degrade with prolonged sun exposure, making synthetic underlayments increasingly popular in modern roofing. For most residential roofs, replacement intervals pertain to the roof system rather than the underlayment alone.
Code And Roofing Standards
Building codes in the United States require appropriate underlayment in roof assemblies and sensible moisture management in wall assemblies. The International Residential Code (IRC) and local amendments govern underlayment choices, installation methods, and weatherproofing practices. Roofing felt standards cover tear resistance, water shedding capability, and compatibility with shingles or tiles. Builders should verify that products meet applicable ASTM or equivalent standards and follow warranty conditions to ensure compliance and performance.
Choosing Between Building Paper And Roofing Felt
- For Walls: Choose building paper or a modern house wrap with a proven air barrier and vapor management performance. Consider climate zone and energy goals when selecting a breathable membrane.
- For Roofs: Use roofing felt as a traditional underlayment or opt for synthetic underlayment for greater durability and easier installation. Evaluate roof pitch, weather exposure, and shingle type when deciding.
- Combined Systems: Some builders use both correct wall moisture control and roof underlayment to optimize performance, ensuring each material functions in its intended location.
Practical Quick Reference
| Material | Primary Use | Breathability | Durability | Typical Climate Fit |
|---|---|---|---|---|
| Building Paper / House Wrap | Wall moisture and air barrier | High (vapor-permeable) | Moderate (with proper installation) | Varies by climate; generally applicable |
| Roofing Felt | Roof deck weather barrier | Low (water shedding, not vapor) | Moderate to high (depends on weight) | Areas with defined roofing systems; modern climates |