“Ash felt roofing supplies” is often used when searching for asphalt felt roofing supplies, the materials and tools used to install traditional roofing underlayment. Asphalt-saturated felt is placed beneath shingles and other roof coverings to provide a temporary layer of water resistance and help protect the roof deck. Choosing the right felt, fasteners, and accessories depends on the roof design, local building requirements, and the roofing manufacturer’s instructions.
What Asphalt Roofing Felt Does
Roofing felt, also called asphalt felt or felt underlayment, is a sheet material made with a fibrous base—commonly organic or fiberglass-reinforced—that is saturated or coated with asphalt. It is installed over the roof deck and beneath the finished roofing material. Common products include No. 15 and No. 30 felt, although modern packaging may identify them by approximate weight, such as 15-pound or 30-pound underlayment.
Felt is not a substitute for shingles, metal panels, or another finished roof covering. Its job is to serve as a secondary layer beneath that covering. It can help limit water intrusion from wind-driven rain, protect the deck during construction, and separate the roof covering from the wood surface. The level of protection depends on the product, installation, roof slope, exposure conditions, and details such as valleys and penetrations.
Underlayment options also include synthetic products and self-adhered membranes. These materials can differ substantially in weight, tear resistance, exposure limits, and installation requirements. They should not be treated as interchangeable without checking the roof covering manufacturer’s specifications and applicable building code.
Common Asphalt Felt Roofing Supplies
A complete roofing supply list includes more than rolls of felt. The roof’s size and shape, the type of roof covering, and local requirements determine what is needed. A typical materials and tools list may include:
- Asphalt felt rolls: Select a product suitable for the roof covering and intended application.
- Roofing nails or cap fasteners: Use fasteners appropriate for the underlayment, deck, and exposure conditions.
- Drip-edge flashing: Metal edging helps direct water at eaves and rakes; installation sequence varies by location and code.
- Roofing cement or compatible sealant: Used only where the roofing system’s instructions call for it.
- Flashing materials: Components for chimneys, walls, valleys, vents, and other roof transitions.
- Measuring and cutting tools: A tape measure, chalk line, utility knife, and straightedge help with layout and trimming.
- Safety equipment: Fall protection, appropriate footwear, eye protection, and other job-site controls.
These items are not a universal specification. For example, some systems use specialized fasteners or require a self-adhered membrane in particular areas. The product label and installation instructions should guide the final supply list.
Choosing Between No. 15 And No. 30 Felt
No. 15 and No. 30 are familiar names for asphalt roofing felt. Historically, the numbers referred to approximate weight per roofing square, a measure of 100 square feet. Product specifications and labeling have evolved, however, so the number alone should not be used as a precise statement of a roll’s current weight or performance. Check the manufacturer’s data sheet for actual coverage, dimensions, material properties, and installation guidance.
In general, heavier felt is often selected where added toughness is desired, while lighter products may be easier to handle. The right choice depends on the roofing system and the roof’s conditions—not simply on which roll appears more durable. A product that is not approved for a particular covering, slope, or installation method may be unsuitable despite its weight.
| Supply consideration | What to check |
|---|---|
| Underlayment type | Confirm that the roofing manufacturer permits the product beneath the selected roof covering. |
| Roof slope | Review the code and installation instructions for low-slope requirements and additional layers. |
| Exposure during construction | Check how long the underlayment may remain uncovered and whether weather can affect it. |
| Fasteners | Follow specified type, length, placement, and spacing; requirements can vary by product. |
| Coverage | Use the label’s net coverage and account for overlaps, cuts, valleys, and roof geometry. |
How To Estimate Roofing Felt
Roofing material is commonly estimated in squares. One roofing square equals 100 square feet of roof surface. To estimate the basic felt requirement, measure each roof plane, calculate its area, and add the areas together. Divide the total by 100 to find the number of squares, then compare that figure with the roll’s stated coverage.
The roof’s plan-view footprint is not necessarily its actual surface area. A pitched roof has more area than the building footprint, and hips, dormers, valleys, and other features increase cutting and overlap. For a simple gable roof, a contractor may calculate each sloped plane using its length and slope-adjusted width. Complex roofs require measurements of each plane or a reliable roof measurement.
Allow for the product’s required side and end laps, plus waste from trimming and roof features. A single roll may advertise a nominal coverage figure that does not match the usable area after overlaps. Use the coverage stated on the specific roll rather than relying on a generic estimate. When a project has unusual geometry, a roofing professional or supplier can help calculate quantities.
Installation Basics And Important Details
Asphalt felt is generally installed over a clean, sound roof deck. The installer lays the material in courses, aligns it with the roof edge, and overlaps adjacent sheets according to the product instructions. Fasteners hold it in place, and the next course covers the prescribed portion of the previous one. The exact lap dimensions, fastening pattern, and direction of installation are product- and code-dependent.
Roof edges, valleys, eaves, rakes, and penetrations need particular attention because they are common points of water entry. Drip-edge placement and underlayment sequencing can vary with the roof location and adopted building code. Valleys may require a specified membrane or a particular open- or closed-valley assembly. Chimneys and plumbing vents also need compatible flashing details; felt alone cannot make these transitions watertight.
Underlayment may be damaged by wind, foot traffic, moisture, or prolonged exposure to sunlight and weather. The product’s exposure limit is important when installation and shingle application will occur at different times. Damaged, wrinkled, or wet material may need correction before the finished roof is installed. Roofing felt is not intended to serve as a long-term exposed roof surface unless a specific product is designed and approved for that use.
Roofing work involves fall hazards, especially on steep or elevated surfaces. The Occupational Safety and Health Administration (OSHA) sets construction requirements for fall protection in the United States. Those requirements and safe work practices should be reviewed before work begins. Homeowners should use qualified professionals when roof access, slope, weather, or project complexity creates significant risk.
Roofing Felt, Synthetic Underlayment, And Ice Barriers
Asphalt felt remains a familiar choice, but it is only one type of roof underlayment. Synthetic underlayments are typically made from polymer-based materials and may offer different tear resistance, weight, handling, and weather-exposure characteristics. Self-adhered membranes use an adhesive backing and are often specified in vulnerable areas, such as eaves in cold regions or roof valleys, subject to code and system requirements.
An ice barrier is a specialized water-protective membrane, not simply a heavier roll of felt. In regions where ice dams are a concern, building codes may require an ice barrier at specified roof edges. The location, width, and installation details depend on the adopted code and climate provisions. A contractor should verify local rules rather than assuming that standard felt satisfies an ice-barrier requirement.
Each underlayment type has limitations. A synthetic product is not automatically suitable beneath every roof covering, and self-adhered membrane can have specific substrate and temperature requirements. Compare manufacturer instructions, warranty conditions, and code approval for the complete roof assembly.
Buying Asphalt Felt Roofing Supplies
Roofing felt and related supplies are sold through roofing distributors, building-material suppliers, and some home-improvement retailers. Before purchasing, confirm the roof covering, roof slope, local code, and manufacturer’s approved underlayment. Ask the supplier for a current product data sheet if the label does not clearly state performance and installation information.
Compare products by useful specifications rather than price per roll alone. Check net coverage after laps, roll dimensions, weight, material composition, permitted exposure time, and required fasteners. Also ask whether the product is intended for the roof covering in question and whether the roofing manufacturer recognizes it for the proposed assembly.
When buying for an active job, consider storage and weather. Keep rolls protected from moisture and damage, and follow the manufacturer’s storage instructions. Do not order solely from a building’s floor area: pitch, roof shape, overlaps, and waste can substantially change the quantity needed.
Building Codes, Standards, And Manufacturer Guidance
Roofing requirements in the United States depend on the locally adopted building code, any amendments, and the roof covering manufacturer’s instructions. The International Residential Code (IRC), where adopted, includes provisions for roof underlayment and other roofing components. Local building departments can explain which edition and amendments apply to a specific project.
ASTM International publishes standards relevant to roofing materials, and a product’s technical documentation may identify applicable standards. A standard reference is not, by itself, proof that a product fits every roof system. The installer must also confirm compatibility, installation details, and any warranty conditions for the finished assembly.
For reliable project information, consult the product’s current technical data sheet and installation instructions, the local building department, and a qualified roofing contractor. Useful reference organizations include the National Roofing Contractors Association (NRCA), International Code Council (ICC), ASTM International, and OSHA. Their resources address roofing practice, model codes, material standards, and workplace safety.
Common Mistakes To Avoid
- Choosing by roll name alone: Verify current specifications and intended use instead of assuming all No. 15 or No. 30 products are identical.
- Ignoring roof slope: Low-slope roofs may require different materials or installation details than steep-slope roofs.
- Underestimating quantity: Account for laps, roof features, and the actual coverage printed on the roll.
- Skipping flashing details: Felt does not replace flashing at chimneys, valleys, walls, or vents.
- Leaving felt exposed too long: Observe the product’s stated exposure limit and protect the installation from damage.
- Assuming one method meets every code: Confirm local requirements and manufacturer instructions before installation.
The most dependable asphalt felt roofing supplies are those specified for the complete roof system—not merely products that fit a general description. Verifying material compatibility, coverage, fasteners, flashing details, and local requirements before work starts helps reduce waste and supports a durable, code-compliant roof installation.