Flat Flash

FLAT FLASH roofing underlayment is a 40 mil self-adhering sheet membrane used for sealing at the hip and ridge under the cap of a tile roof. This membrane protects roof substrates against water penetration from wind-driven rain and water entry from under the cap at the hip and ridge area. FLAT FLASH can be used in new construction and re-roofing. The membrane will self-adhere to wood, concrete and masonry.

FLAT FLASH is comprised of a strong, non-thermaling, skid-resistant, cross laminated polyethylene film combined to a peel and stick layer of highly adhesive rubberized asphalt. A siliconized paper release sheet is used to prevent the material from sticking together in the roll and is easily stripped away for installation. The membrane adheres tenaciously to the surface it is in contact with and permanently bonds to itself at the laps. FLAT FLASH provides a seal around nails or other fasteners that penetrate the deck during installation of the tile roof cap.


  • For best results, surfaces to be sealed should be clean, dry and free of any other contaminant that may adversely affect adhesion. Cut FLAT FLASH to desired length and peel off release liner from bottom, taking care not to allow the adhesive to come into contact with itself or any foreign matter.
  • Center the material on the ridge or hip board and loosely lay the tape so there is a slight sagging down into the pans of the tile.
  • Do not stretch FLAT FLASH.
  • Proceed by carefully conforming FLAT FLASH to the contours of tile profile by pressing and smoothing the tape to maximize 100% contact of the tile surface. Pressure is essential to eliminate any wrinkles or trapped air bubbles. Overlaps should be a minimum of 6 inches.
  • Precaution: FLAT FLASH is produced for concealed applications beneath the tile roof ridge or hip caps and is specifically not manufactured for exposed areas.
  • FLAT FLASH has no guarantees or warranties.

Click on link below to download sheet.