Building Paper and Roofing Felt are common materials in US construction, serving as protective barriers and weatherproofing components. This article explains what each product is, how they differ, and when to use them in residential projects. It also covers installation tips, codes, and practical cost considerations to help builders, contractors, and homeowners make informed choices.
What They Are
Building Paper, often called building paper or house wrap in some regions, is a porous sheet used to improve a structure’s moisture control before finish siding is installed. Roofing Felt, also known as tar paper, is a heavy, asphalt-impregnated sheet used as a secondary weather barrier under roofing materials. Both provide some protection against wind-driven rain, but their designs reflect different roles in construction.
Primary Purposes
Building Paper mainly acts as a drainage layer and a vapor permeable barrier beneath siding or siding-related assemblies. It helps reduce air leakage and channels moisture away from the wall cavity. Roofing Felt is designed to protect roof decks during construction and as a primary or secondary underlayment beneath shingles or other roofing systems. It enhances resistance to wind and provides temporary protection against moisture until the roof is finished.
Materials and Construction
Building Paper is typically a lightweight, non-woven or kraft-based sheet with a breathable coating or microscopic perforations that allow vapor to escape while blocking bulk water. Roofing Felt is a heavier asphalt-impregnated sheet, often reinforced with fiberglass or organic mats, which provides greater water resistance on the roof deck. The choice of material affects flexibility, puncture resistance, and long-term performance in different climates.
Performance and Weather Barriers
In exterior walls, Building Paper supports moisture management but relies on proper flashing and drainage planes to prevent water intrusion. It is usually combined with a house wrap system or a rainscreen to maintain air quality and reduce mold risk. Roofing Felt offers a more robust barrier for roofs, especially in areas with heavy rainfall or blowing rain. It slows liquid water penetration during wind-driven events and helps protect attic spaces before the final roofing is completed.
Application and Installation
Building Paper is installed horizontally or vertically over wall sheathing, with seams overlapped and fastened to studs. It must be compatible with flashing where windows, doors, and penetrations occur. Roofing Felt is laid with a prescribed slope and shingle exposure, typically overlapping rows to shed water. Proper nailing patterns and wind-resistance considerations are essential to prevent blow-off in high-wind zones. Both products require clean, dry surfaces and careful handling to avoid tearing.
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Code, Standards, And Regional Practices
Building Paper and Roofing Felt are governed by building codes that specify vapor control, air barrier requirements, and installation methods. In many US regions, Building Paper has evolved toward advanced house wraps that improve energy efficiency and air sealing. Roofing Felt requirements vary with roof type and climate, with newer self-adhering underlayments replacing traditional felts in some markets. Local codes and manufacturer guidelines should be consulted for specific nailing patterns and overlap distances.
Durability and Longevity
Building Paper is not designed for long-term exposure on walls; its lifespan depends on continued protection by siding and flashing. When used correctly, it aids moisture management but can deteriorate if water penetrates the exterior envelope. Roofing Felt is designed for roof deck longevity, yet its protective value diminishes if the final roof system is not installed promptly. In both cases, improper installation can lead to mold risk, warped sheathing, or costly repairs later.
Costs And Availability
Building Paper and Roofing Felt are generally affordable relative to other weather barrier products, though costs vary by thickness, weight, and brand. Roofing Felt tends to be more expensive per square than basic building paper due to its heavier composition and waterproofing properties. Availability is widespread in lumberyards and home improvement stores, with many regional variants tailored to climate and building practices.
Choosing For A Project: Quick Guide
- Roofing projects: Prefer Roofing Felt or a self-adhering roof underlayment for primary moisture protection and wind resistance on the roof deck.
- Wall assemblies: Use Building Paper or a modern air barrier/house wrap that provides vapor permeability and drainage; ensure compatibility with flashing and siding.
- Climate consideration: In wet climates, prioritize products with robust water resistance and proper detailing around penetrations; in dry climates, focus on vapor management and airtightness.
- Installation timing: Install wall barrier early in framing; roof underlayment should be installed after decking and flashing, before shingles or tiles.
- Code compliance: Check local code requirements for vapor barriers, air barriers, and underlayment types to ensure proper performance.
Maintenance, Replacement, And Best Practices
Routine inspection of exterior walls and roofs helps identify failed barrier components. If moisture intrusion occurs, address leaks promptly and review flashing, seals, and material compatibility. When remodeling, consider upgrading to modern house wraps with superior air sealing capabilities and drought resistance. For retrofits, ensure that any older tar paper or felt on roofs is replaced if damaged or nearing the end of its expected life.
Environmental And Safety Considerations
Both materials have environmental implications based on raw materials and disposal. Roofing Felt contains asphalt, which has specific handling considerations, while Building Paper often uses recycled fibers in modern formulations. Proper disposal and recycling options should be explored, and installers should follow safety guidelines for handling dust, fibers, and adhesives.
Summary Of Practical Differences
Building Paper excels as a breathable wall barrier and moisture-management layer, emphasizing drainage and vapor control behind siding. Roofing Felt provides stronger water resistance and protection on roof decks, serving as a temporary or secondary waterproofing layer until the final roof is installed. The best choice depends on the project (wall vs. roof), climate, and local code requirements. For many modern builds, advanced self-adhering underlayments and high-performance house wraps are preferred, but traditional Roofing Felt remains a viable option where appropriate.