Roofing Underlayment for Tile, Shingle and Metal Roofs

New SBS Modified Asphalt waterproof roof underlayment compare to felt

LayfastSBS – Superior Elastomeric Modified Asphalt Underlayment for Tile, Shingle, and Metal Roofs

Our Layfast SBS modified bitumen roofing underlayment productsMost of the quality tile, shingle, and metal roofing manufacturers offer 30+ year warranties — these usually cover deterioration of tile and shingle only.  Since the underlayment is the only moisture barrier used in the assembly, employing an inferior underlayment with a shorter life expectancy will compromise the system’s integrity.

Addition of SBS rubber to asphalt gives Layfast an elastomeric property that is not available in common felt.  Layfast SBS contains a higher percentage of asphalt for increased waterproofing.  Its inorganic fiberglass reinforcement eliminates the rot and deterioration associated with saturated felt.

The majority of architects and contractors have realized the necessity of a better underlayment, such as self-adhesive membranes, for valleys and eaves.  Most self -adhesive membranes are manufactured with SBS-modified asphalt, which is the same compound used in Layfast SBS.  By specifying Layfast in the field and a self-adhesive membrane in valleys and eaves, you are specifying a 100% SBS underlayment system throughout the roofing system and prolonging the waterproofing capability.  In contrast to self-adhesive membranes Layfast is mechanically fastened, thus allowing the system to breathe.

Layfast SBS . . . Superior to Felt.  Here’s Why:

  • Economical:
    For pennies more, offer a superior product to your customer.  Typical increased cost to use Layfast in place of felt is about $0.02–$0.08/square foot.
  • Less Decomposition:
    Fiberglass reinforced (inorganic) does not rot like felt.  Felt is reinforced with recycled paper — and you have seen what happens to paper products, like newspaper, after they are left out in the weather.
  • More Elastic:
    SBS rubberized asphalt provides a more pliable and elastic membrane.  Minimizes buckles and wrinkles by laying flatter and smoother . . . saving time.
  • Durable:
    Side laps do not curl up over time.  Does not scuff or tear easily and is less susceptible to damage from other trades.
  • Proven Track Record:
    Layfast has been used successfully for more than 20 years.

Layfast SBS is available in three weights.

Technical Information (nominal)Layfast SBS
Layfast SBS
Layfast SBS
Weight lbs/roll788868
Weight lbs/100 sq. ft.
Coverage per Roll2 Squares2 Squares 1 Square
RECOMMENDED USAGETile/ Shingle/ MetalTile/ Shingle/ MetalTile/ Shingle/ Metal

For samples and technical questions, please contact us at:

188 S. Teilman Ave.
Fresno, CA 93706-1334 U.S.A

Phone:         800-621-9281
Fax:            559-233-4607

For Architects and Specification Writers
Since Layfast is still mechanically fastened (like 30/40# felt), there is no change in drawings/specifications.  To specify Layfast, insert the following language in thetile/shingle/metal roof specification section where the underlayment is specified. For tile and metal roofs, we recommend the use of TU70; for shingle roofs, we recommend the use of TU43.


Underlayment shall be LayfastSBS TU70/TU43, as manufactured by MBTechnology (800-621-9281).  The membrane shall comply with all requirements as outlined in ASTM D226 standards for underlayment and approved by ICC.  Application shall be done in accordance with manufacturer’s most recent specification manual.  Minimum requirements:

Safety Consideration:
Contractor shall observe all safe roofing practices as required by OSHA and local codes.  Use caution when walking on steep slope especially when the surface is slippery and dusty.  Failure to use required safety gear, footwear and equipment can result in serious injury.

Placing material and tile on roof:
Certain tiles with minimal contact with surface of layfast SBS may be prone to sliding especially when temperature is over 100 (F).  Appropriate measures such as installation of a batten system, reducing number of tiles will address this issue.  Contractor shall also use roof jacks, toe board or storage platforms secured to the underlying roof deck to prevent slippage of stored roofing materials.

SBS Rubberized Asphalt

Fiberglass Mat

Minimum of 43—70 -lb./100 sq. ft.

Breaking Strength:
MD 65 lb./in. ASTM D226, CD 46 lb./in.