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Roof Underlayment

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SKU 894393

Membrane Roll for Low Slope Roofing Tri-Ply APP Granular Cap Sheet White 39.625 in. x 32.25 ft. (100 sq. ft. net)

Original price $123.05 - Original price $123.05
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About This Product Tri-ply app Granule is a robust, durable membrane ideal for new constructions or reroofing projects, and can also be used as fla...

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SKU 276849

Self Adhering Starter Roll 33 lin. ft.

Original price $32.02 - Original price $32.02
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About This Product Starter Roofing Shingle Roll - the essential first layer of a weather-tight roof. This product is compatible with all Owens Corn...

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SKU 022265

Roof Underlayment Roll, Synthetic, ProArmor, 1001 sq. ft.

Original price $108.57 - Original price $108.57
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About This Product Synthetic Roof Underlayment with Fusion Back Coating Technology is robust, long-lasting, and water-repellent. It is also lightwe...

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SKU 013005

Roof Underlayment, Felt, 216 sq. ft.

Original price $37.20 - Original price $37.20
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$37.20
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About This Product APOC organic felts are crafted with specialized technology that ensures rain and water stay outside your home while allowing wat...

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SKU 117608

Membrane Roll 3 ft. x 33 ft. for Low Slope Roofs Tri-Ply APP Smooth Modified Bitumen(100 sq. ft. net)

Original price $123.05 - Original price $123.05
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About This Product Tri-ply APP Smooth is a sturdy, durable membrane suitable for both new roofing projects and reroofing, as well as for use as fla...

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SKU 325167

Membrane Roll for Low Slope Roofs Tri-Ply #75 Base Sheet 3 ft. x 100 ft. (300 sq. ft. Net)

Original price $69.25 - Original price $69.25
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About This Product Self-Adhering Roofing Systems are installed without the use of torches, open flames, hot asphalt, or solvent-based adhesives. Ke...

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SKU 438455

Cap Roll Roofing White Fiberglass Mineral-Surfaced 3 ft. x 36 ft. 100 sq. ft. Coverage

Original price $56.84 - Original price $56.84
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About This Product Fiberglass mineral surfaced roll roofing is a product coated with asphalt and reinforced with glass fibers. The surface made of ...

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Roof Underlayment: What You Need to Know

Roof underlayment, also known as roofing felt, membrane sheets, or protective roofing barriers, serves as a critical moisture-resistant layer between the roofing deck and shingles or panels. Designed for added durability and leak prevention, underlayment enhances weatherproofing, UV protection, and insulation efficiency. Available in various materials and configurations, it ensures long-term structural integrity for both residential and commercial roofing systems.

Types:

  • Synthetic Underlayment: A lightweight, high-performance alternative to traditional felt, synthetic underlayment provides superior tear resistance, waterproofing, and UV stability. It is ideal for steep-slope roofing applications requiring extended exposure before shingle installation.
  • Felt Underlayment (Asphalt-Saturated): A cost-effective and time-tested option, felt underlayment offers basic water resistance and reinforcement under shingles. Available in 15-pound and 30-pound grades, it provides varying levels of durability and thickness.
  • Self-Adhering Membrane: Featuring an adhesive backing for secure attachment, self-adhering underlayment offers exceptional water resistance and wind uplift protection. Often used in low-slope roofing systems and ice-prone regions, it acts as a secondary waterproofing layer in critical areas.

Technical Applications:

  • Waterproofing Barrier: Roof underlayment serves as a secondary moisture defense, preventing water infiltration from wind-driven rain, ice dams, and roof leaks.
  • Slope Compatibility: Synthetic and felt underlayment can be used on steep-slope roofing, while self-adhering membranes are designed for low-slope applications where added sealing is necessary.
  • Fire & UV Resistance: Many synthetic underlayment options feature fire-resistant coatings and UV protection, allowing longer exposure before final roof installation.
  • Enhanced Roof Longevity: By preventing deck rot, mold growth, and premature material degradation, underlayment extends the lifespan of the roofing system.

Why Choose Supply Ontime?

At Supply Ontime, we offer reliable materials designed to meet your project’s needs. With same-day delivery across the Greater Los Angeles area, we make it easy to keep your projects on schedule. Order Roof Underlayment now and get it delivered today!

Roof Underlayment FAQ

When should I use roll roofing versus traditional underlayment?

Roll roofing (mineral-surfaced bitumen) can serve as both underlayment and finished surface on sheds or low-slope roofs. Underlayment membranes are installed under shingles, tile, or metal roofs to provide an extra water barrier. LA’s winter rains and seismic codes make underlayment essential for all pitched roofs. Roll roofing is better suited for small structures where cost efficiency is key. Traditional underlayment is the preferred choice for long-term durability in homes.

Are these underlayments compatible with asphalt shingles and tile?

Yes. The self-adhering and APP rolls sold by Supply Ontime are designed for use beneath asphalt shingles, cedar shakes, or clay tiles. Always check manufacturer specifications for temperature limits; high-temperature underlayments are recommended for dark roofs in sunny climates. These products are engineered to bond well even in coastal humidity. Using compatible underlayments helps ensure warranties remain valid.

What roof-underlayment products does Supply Ontime stock?

They offer self-adhering starter rolls, asphalt-saturated rolls, and APP-modified membrane rolls. Options include 33-linear-ft starter strips and tri-ply APP cap sheets for low-slope roofs. These underlayments are designed to enhance waterproofing and extend the service life of roofing systems. Contractors often use them to meet both residential and commercial code requirements.

Can Supply Ontime meet tight delivery schedules for underlayment?

Underlayment rolls are bulky and heavy. Supply Ontime provides same-day delivery or scheduled two-hour slots to job sites. Include any hoisting requirements or rooftop access instructions when ordering. Customers can request truck bed, curbside, or white-gloves delivery depending on the job site. Planning ahead avoids delays in starting roof work.