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Crete-Flex Stainless Steel Masonry Screw


The Crete-Flex screw is manufactured from a 410 stainless steel for added rust resistance in moist atmospheres. It is used for attaching an item to masonry surfaces such as block CMU, brick or concrete.

Head Styles

The Crete-Flex screw is manufactured in a flat head countersunk with a #3 phillips drive for use where the head must sit below the surface of the item being attached.  The flat headed screw is measured as an overall length including the head.  There is also a head style of a slotted hex washer head which requires the use of a 5/16”driver and for use in applications where the head will protrude above the surface of the item being attached.  The length of the hex head is measured from underneath the head.


The Crete-Flex masonry screw comes in only one diameter of 1/4”.  When reading the description of the screw, the first number refers to the diameter.


Crete-Flex screws come in nine different lengths with the shortest length of 1-1/4” and the longest length of 6”.  When reading the description of the screw, the second number refers to the length.

Diameter of Hole

A 7/32” diameter hole must be drilled into the base material using a hammer drill and a carbide tipped masonry bit that meets ANSI standards.  Hole size is critical for ensuring proper tolerance and for obtaining minimum holding values of the screw in the masonry material.

Depth of Hole

The depth of the hole in the base material must be a minimum of 1/4” deeper than the Crete-Flex screw will penetrate (see minimum embedment requirements below). This will ensure that the minimum embedment requirements are met, as well as providing space for dust created during the installation process to fall and remain out of the way.


  • Minimum Embedment – all Crete-Flex screws must be embedded into the base material at least 1” in order to obtain minimum holding values in the base material.
  • Maximum Embedment – the maximum embedment in the masonry material for all lengths of Crete-Flex screws is 1-3/4”.

Thickness of Material Being Fastened

Each length of Crete-Flex masonry screw is designed to fasten a range of thicknesses of materials.  The minimum length screw used for any application is determined by adding the minimum embedment depth of 1” to the thickness of the material being fastened.  The maximum length of screw is equal to the maximum embedment of 1-3/4” plus the thickness of the material being fastened.

Hole Size in Material Being Fastened

To install a Crete-Flex through a predrilled hole in the item being attached, it is important that the hole is 5/16” in diameter.


All Crete-Flex screws are packaged 100 pieces per box with one 7/32” carbide tipped bit included.

Installing Crete-Flex screws:

  1. Drill a hole in the base material using a hammer drill and a 7/32" carbide tipped drill bit that meets ANSI standards
  2. Make sure that the hole is drilled a minimum of 1/4" deeper than the screw that is being used will penetrate the masonry.
  3. Using compressed air, wire brush or vacuum, clean the hole of all dust.
  4. Insert the Crete-Flex stainless steel screw through the fixture and into the hole in the base material.
  5. With a #3 phillips driver for the flat head or a 5/16” hex driver, drive the Crete-Flex stainless steel screw into the hole by tapping threads until the head of the screw is tight against the surface of the material being fastened.

Holding Values

Use this link to obtain technical information on Crete-Flex stainless steel masonry screws.


Please remember with all fastening jobs to keep safety in mind. Always follow safety instructions on all tools, and refer to manufacturer's installation instructions when available and always remember to wear safety goggles!

Article written by: Bob Carlisle, President Concrete Fastening Systems, Inc

Concrete Fasteners
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