Gorilla Guard® SPEC 30 Engineered Roof Underlayment

Gorilla Guard® SPEC 30 is a high performance, engineered roof underlayment for steep slope roof applications. It outperforms traditional #30 specification organic felt through innovation and technologically advanced substrates. Its proprietary formulation and manufacturing process creates a unique substrate with increased performance and durability.

Gorilla Guard® SPEC 30 meets shingle underlayment requirements for the Atlas Signature Select® roofing system.


Gorilla Guard Spec 30 Multiroll

  • 142% Stronger In Pull-Through Test*
  • 207% Higher Tear Strength*
  • 277% More Breaking Strength (MD)*
  • 280% Stronger in Peel Resistance Test*
    ...And It’s 40% Lighter!

Installation Instructions

Gorilla Guard® SPEC 30 shall be applied to a properly prepared dry deck that is smooth, clean and free from any depressions, projections, or protruding nails. Roof decks shall be structurally sound and meet or exceed minimum requirements of the deck manufacturer and local codes.

Always lay the Gorilla Guard® SPEC 30 parallel to the eaves, lapping each course at least 2" over the underlying course. Apply the drip edge underneath the Gorilla Guard® SPEC 30 along the eaves and over the Gorilla Guard® along the rakes. Gorilla Guard® SPEC 30 should never be applied perpendicular to the eaves. Secure the Gorilla Guard® SPEC 30 with fasteners every 12" across the lower and upper edge to hold it in place. If more than one piece is required to continue a course, lap the ends at least 4". End laps in succeeding courses should be located at least 6' from end laps in the preceding course. Lap the Gorilla Guard® SPEC 30 a minimum of 6" from both sides over all hips, ridges and valleys. Where a roof meets a vertical surface, carry the underlayment at least 4" up the surface.

On decks having a slope greater than 4" per foot, one layer of Gorilla Guard® SPEC 30 should be applied. Some local codes may require specific underlayments. On slopes 2" to 4" per foot apply a double layer of Gorilla Guard® SPEC 30 over the entire deck surface. Starting with a 19" wide strip at eaves, overhanging the eaves 1/4" to 3/8", cover with full 36" strips providing a 17" exposure. Continue with 36" strips lapping each course 19" over the preceding course. End laps for low slopes shall be 12" and staggered 6' apart.

The use of Gorilla Guard® SPEC 30 along with the proper decking materials and shingles will help in meeting Class A and or Class C Fire ratings. A shingle by itself is not fire-rated, although it is part of the roofing assembly.


KEEP ROLLS DRY AND COMPLETELY PROTECTED FROM THE WEATHER. If work is to be done in cold weather, rolls of roofing should be placed in a warm place for 24 hours prior to application.

*Tip: Cut Gorilla Guard® SPEC 30 into manageable lengths for safety on the roof.