Blok-Flash® by Mortar Net®

A Unique Embeddable Flashing System

Blok-FLASH® is an embeddable flashing device for exterior single-wythe C.M.U. wall systems. It collects moisture that infiltrates the wall and flows down the vertical cores and diverts it to the exterior.

Blok-FLASH is useful at all flashing/weep hole locations including base wall, above door and window openings, above bond beams, in parapet walls, basements and any other locations where flashing is necessary.


  • Useful in all 8", 10", and 12" exterior block wall applications
  • Maintains greater bond than through-wall membrane flashing
  • Eliminates the need for using multiple sizes of architectural C.M.U., thus reducing costs
  • Simple installation in reinforced wall systems
  • Reduces thermal break, helping to maintain the walls R-value insulation integrity
  • Saves more than half of the labor an material costs associated with using membrane flashing in a multiple-wythe course
  • 45-degree drip edge to deflect moisture away from the wall system
  • Concaved weep spout for ease of tooling
  • Eliminates unsightly head joint weeping devices
  • Light weight and compact shape for convenient shipping, handling and storage
 Model US-8Model US-10Model US-12
C.M.U. Type 8" (7-5/8") 10" (9-58") 12" (11-5/8")
Height .3125" (7.94mm) .3125" (7.94mm) .3125" (7.94mm)
Width 5.625" (142.88mm) 7.625" (193.68mm) 9.625" (244.48mm)
Length 6.75" (171.45mm) 6.75" (171.45mm) 6.75" (171.45mm)

Blok-FLASH® is a high-density polyetheylene composition molded in to a .0625" thick (1.59 mm) flashing pan with .3125" (7.94 mm) perimeter flanges.

The .0625 inch (1.59 mm) concave weep spout with a .20" (5.08 mm) x .64" (16.26 mm) opening and a 45-degree drip edge extends 1.0" (25.4 mm) from the outer flange. The inner and outer flanges are spaced to allow for 1.0" of mortar bond between the upper and lower course of C.M.U. in 8", 10" or 12" wall systems.

The weep spout ceiling extends 3.5" (88.9 mm) from the outer flange into the center of the pan and acts to suspend mortar, keeping the weep channel clear.

Blok-FLASH® is impervious to water and includes chemical stabilizers to protect against UV degradation.

Blok-Flash® by Mortar Net®

For Product Information Call:


Colors, product data, and availability are subject to change without notice. Please confirm all details with a County Materials representative for availability in your area. Colors shown may vary from actual hues and should only be used as a guide. Refer to actual product samples for final color selection.