Meta description: Learn what 90-pound roofing paper is, how it differs from roofing felt, where it can be used, and what to check before installation.
“90 weight roofing paper” usually refers to a heavy asphalt roofing roll commonly called 90-pound roofing or 90-pound roll roofing. Despite the word “paper,” it is not ordinary paper and is not always the same product as the felt underlayment installed beneath shingles. Its weight, surface, intended use, and installation requirements matter when planning a roof repair or replacement. Knowing those differences helps homeowners compare materials, avoid using an underlayment as an exposed roof, and check whether a product is appropriate for a particular roof and local building requirements.
What Is 90-Pound Roofing Paper?
In roofing, “90-pound” commonly describes a roll-roofing product associated with roughly 90 pounds of material per roofing square, or 100 square feet. The exact product specifications and usable coverage depend on the manufacturer. A roofing square is a measurement of roof area, not the dimensions of a roll.
Traditional 90-pound roll roofing is generally made from an asphalt-saturated roofing base with a mineral-granule surface. The asphalt helps resist water, while the granules protect the surface from sunlight and weather. Some products may have different constructions or specifications, so the label and manufacturer’s data sheet are more reliable than the product nickname alone.
The term can cause confusion because people also use “roofing paper” to mean roofing felt or underlayment. These products are installed beneath a finished roof covering, such as shingles, and are not necessarily designed to remain exposed. A roll’s weight does not establish that it is suitable as underlayment or as a finished roof. Its listed application does.
How 90-Pound Roll Roofing Differs From Roofing Felt
Roofing felt is typically an asphalt-treated sheet used as a secondary water-shedding layer beneath roofing materials. Asphalt-saturated felt products are commonly identified by product standards and classifications rather than simply by a “90-pound” label. Synthetic underlayments are another category, made from polymer-based materials and carrying their own installation requirements.
By contrast, 90-pound roll roofing is often a surfaced roofing material intended to serve as an exposed roof covering on eligible applications. It may be considered for certain small or low-slope roof areas, depending on the product instructions and local code. It is not a direct substitute for a shingle underlayment, nor does it automatically qualify as a complete roof system.
| Feature | 90-pound roll roofing | Roofing felt or underlayment |
|---|---|---|
| Typical role | Exposed roofing on approved applications | Secondary layer beneath a roof covering |
| Surface | Often mineral-granule surfaced | Usually a comparatively smooth sheet |
| Weather exposure | Designed for exposure when installed as directed | Often intended to be covered by the finished roof |
| How to identify it | Product label, intended-use statement, and installation guide | Standard, classification, and underlayment instructions |
Terms such as “90-pound felt” can also appear in product listings or informal conversation. Because naming is not always consistent, buyers should check the package for the product type, applicable standard, approved uses, coverage, and installation instructions before purchasing.
Where 90-Pound Roofing May Be Used
Manufacturers may specify 90-pound roll roofing for certain low-slope roofs, sheds, porches, garages, additions, or other small structures. The actual suitability depends on the specific product, roof slope, roof deck, climate exposure, and installation method. A product labeled for a particular application should not be assumed suitable for every flat or low-slope roof.
Low-slope roofs need particular care because water drains more slowly than it does on a steep roof. A roof covering that is acceptable on one slope may be unsuitable on a shallower one. Manufacturers may state a minimum slope and require specific laps, fasteners, cement, or a base sheet. Local building codes can impose additional requirements, including requirements for the roof assembly, fire classification, wind resistance, and underlayment.
For an existing roof, the condition of the deck and drainage system is just as important as the roll material. Soft or damaged sheathing, standing water, poorly placed drains, and inadequate edge details can undermine a new covering. Roll roofing is not a fix for a persistent drainage or structural problem.
Advantages And Limitations
Potential advantages
- Relatively simple material format: It comes in rolls and can cover an area with fewer individual pieces than many small-format coverings.
- Mineral surface: Granules can shield the asphalt surface from direct sunlight when the product is installed as an exposed covering.
- Useful for some modest roof areas: Where the product is approved and correctly installed, it may be a practical option for certain auxiliary structures.
- Clear product instructions: Established roofing products generally provide requirements for slope, laps, fastening, and roof preparation.
Important limitations
- Application is limited: It is not an all-purpose roofing material and may not meet the requirements for a home’s main roof.
- Installation details are critical: Incorrect overlaps, fasteners, flashing, or edge treatment can create leak paths.
- Appearance and service life vary: Product quality, installation, roof slope, weather, maintenance, and exposure all affect performance.
- It is not a substitute for proper underlayment: A surfaced roll product and a separate underlayment perform different roles unless the manufacturer specifies otherwise.
No roofing material guarantees a particular service life in every setting. Product warranties also have conditions and may not cover damage from improper installation, inadequate ventilation, ponding water, or use outside the stated application.
How To Choose The Right Product
Before buying 90-pound roofing paper, identify the roof’s slope and intended use, then compare that information with the product’s technical data sheet. The packaging should clearly say whether the material is roll roofing, underlayment, or another roof component. If the label is ambiguous, the manufacturer or a roofing supplier can confirm the intended application.
- Check minimum slope: Confirm that the roof’s measured slope meets the product’s requirement. Do not estimate by appearance alone.
- Confirm roof-deck requirements: Review approved substrates, deck condition, and any required base sheet or underlayment.
- Review fastening and lap details: Find the specified fasteners, exposure, side laps, end laps, and any required roofing cement.
- Check local code: Requirements vary by jurisdiction and project. A local building department can explain applicable permit and inspection rules.
- Compare coverage, not just roll weight: Laps and trimming reduce the area a roll covers. Use the manufacturer’s stated coverage for the intended installation.
- Consider the complete assembly: Flashing, drip edges, valleys, penetrations, ventilation, and drainage must be compatible with the roofing system.
For a home’s primary roof, it is wise to compare the proposed material with alternatives designed for that roof type. A qualified roofer can assess slope, ventilation, drainage, and local requirements rather than selecting a material based only on its weight or price.
Installation Considerations
Installation must follow the exact product instructions. Roll roofing products differ in how they are laid, fastened, and sealed, so a generic method is not a reliable substitute for the manufacturer’s guide. The instructions may call for a particular starting edge, direction of installation, lap width, fastening pattern, and treatment at roof edges and penetrations.
The roof deck should be sound, dry, clean, and prepared as specified. Existing roofing may need removal if it is damaged, uneven, or incompatible with the new system. Installing over wet or deteriorated sheathing can conceal problems and compromise the new roof. Repairs to flashing and deck damage should be completed before the roll material is installed.
Water-shedding details deserve close attention. Roof edges, walls, chimneys, plumbing vents, and other penetrations can interrupt the surface and require correctly integrated flashing. Simply covering a joint with roofing cement does not necessarily create a durable or code-compliant detail. The product guide and applicable roofing standards should direct these transitions.
Roof work also presents fall, tool, and heat-related hazards. Roof surfaces can become slippery, and work near edges can result in serious injury. Appropriate fall protection and safe handling are essential. Some roofing adhesives or asphalt products require ventilation and precautions stated on their safety data sheets. Homeowners who are uncertain about safe access or installation should use a qualified professional.
90-Pound Roofing Paper Compared With Common Alternatives
Choosing a roof covering depends on the building and the roof system, not solely on material weight. The following comparison describes broad differences; specific products can vary considerably.
| Material | Common role | Key consideration |
|---|---|---|
| Asphalt shingles | Finished covering for many sloped residential roofs | Require compatible underlayment, flashing, and suitable slope |
| 90-pound roll roofing | Exposed covering on certain approved applications | Follow its slope limits and detailed installation instructions |
| Asphalt-saturated felt | Underlayment beneath a roof covering | Usually requires coverage by the finished roofing material |
| Synthetic underlayment | Underlayment beneath shingles or other approved coverings | Product-specific fastening, exposure, and installation limits apply |
| Single-ply membrane | Low-slope or flat-roof system | Seams, attachment, flashing, and drainage are system-specific |
For many low-slope roofs, a membrane system may be more appropriate than roll roofing, but the right choice depends on design, code, budget, and installer expertise. For steep-slope homes, shingles, metal, tile, or other coverings may be more suitable. A roofing professional can compare complete systems rather than isolated materials.
Common Mistakes To Avoid
- Assuming “90-pound” means 90 pounds per roll: The traditional description is associated with weight per roofing square; packaging specifications should be checked.
- Confusing roll roofing with underlayment: A roll that looks like roofing paper may not be designed for the same purpose as felt or synthetic underlayment.
- Ignoring roof slope: A product used below its approved minimum slope may be vulnerable to water intrusion and may violate code or warranty conditions.
- Skipping flashing and drainage work: A new surface cannot compensate for defective transitions, clogged drains, or ponding water.
- Relying on an old installation method: Product formulations and instructions differ. Current manufacturer guidance should take precedence over assumptions based on a previous roof.
- Choosing by price alone: The cost of a roll does not include preparation, flashing, labor, waste, or repairs to the underlying deck.
What To Verify Before Starting A Project
A short review before purchase can prevent costly material and installation mistakes. Confirm the product name and intended use, required slope, coverage after laps, roof-deck preparation, approved fastening method, and flashing details. Check whether a permit is required and whether local rules specify materials or installation standards. Keep the product instructions and warranty information with the project records.
For authoritative guidance, consult the product manufacturer’s current installation guide and technical data sheet, the local building department, and applicable provisions of the International Residential Code as adopted and amended locally. Roofing standards published by ASTM International can also help identify product classifications, but a standard designation does not replace the manufacturer’s application instructions or local code review.
In short, 90-pound roofing paper is generally a name for a heavy, often mineral-surfaced roll-roofing product—not a universal term for roofing felt. The label, approved roof slope, installation details, and local requirements determine whether a particular roll is appropriate for the job.