MB TU43 Layfast SBS Modified Asphalt Reinf. 40# Underlayment, 33 Rolls - MB Tech. TU43 Layfast SBS Mod. Asphalt Underlayment / Base Sheet with Fiberglass Mat. Use under Tile / Shingle Requiring 40# Underlayment. Mechanically Fastened. 3.31x64.75 ft Rolls (2-Sq). 33 rolls/Pallet. Price/Pallet. (see detail view order notes)
MB TU43 Layfast SBS Modified Asphalt Reinf. 40# Underlayment, 33 Rolls
$2,229.00 SALE $1,429.95
(Savings: $799.05)
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MB Tech. TU43 Layfast SBS Modified Asphalt Underlayment / Base Sheet. Reinforced w/ Fiberglass Mat. Lays Very Flat. Use under Tile / Shingle for Jobs Requiring 40# Underlayment. Mechanically fastened. 3.31x64.75 ft Rolls (2-Square Rolls). 33 rolls/Pallet. Price/Pallet.

Ordering Notes:

  • Shipping leadtime: 2-4 business days.


The open mesh construction of the asphalt coated fabric allows the surface coatings to penetrate through and interlock, thereby providing a firm mechanical bond between coatings, and insuring long life of the application. This strong elastic interlocking system is very pliable and prevents rupture due to expansion and contraction of the applied surfaces.


SBS modified underlayment for use under tile, shingle roofs. Lays flat during application. Higher tensile, tear and weight compared to 30 and 40# felt. Ideal for jobs requiring a 40# grade underlayment.


  • SBS modified asphalt underlayment/base. Reinforced with fiberglass mat.
  • Much higher tensile strength than standard asphalt cotton.
  • 20 x 10 thread count provides larger mesh openings, improving bitumen saturation and penetration.
  • Suitable for Hot or Cold applications.
  • High Tensile strength yet very lightweight.
  • Will not rot, mold or mildew. 
  • Meets ASTM D1668, Type I & Fed. Spec. HH-C-466b
  • Dimensionally stable and free of defects.
  • Will unroll and handle easily in normal installation.
  • The asphalt saturated fabric unrolls easily, without distortion.
  • The treated fabric can be applied smoothly and without wrinkles.


  • Higher tear resistance
  • Increased longevity
  • More protection
  • More water resistant


  • Weight: 88 lbs./roll
  • Width/Length: 39-3/4 inch / 64 ft. 4 inch
  • Reinforcement: Fiberglass
  • Application: Mechanically fastened
  • Coverage: 2 squares/roll
  • Rolls Per Pallet: 33



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similar product terms: SBS modified asphalt underlayment, shingle roofs, layfast underlayment, layfast SBS, mb technology, roof underlayment, steep roofing, valleys, eaves, tile roofs, metal roofs, high pitched roofs

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