Backer-On® cement screws are designed for attaching Hardie-Backer® cement board and Rock-On® cement board screws are designed for attaching Durock® cement board to wood or light gauge steel studs. They can be used for the following applications and the recommended number of screws to use per 3×5 board.
Countertop Installation – 54 screws / 3×5 board
Floor Installation – 48 screws / 3×5 board
Wall Installation – 26 screws / 3×5 board
Ceiling Installation – 30 screws / 3×5 board
1. A standard screwgun with a depth sensitive nosepiece should be used to install cement board
fasteners. For optimal fastener performance, use a screwgun with adjustable depth of drive
and variable RPM (0-2000).
2. Adjust the screwgun nosepiece to properly seat the fastener.
3. Use enclosed T-25 Star Drive bit to drive in the cement board – worn or damaged bit tips should
4. The fastener is fully seated when the head is flush with the work surface.
5. Overdrivng may result in torsional failure of the fastener or stripout of the substrate.
6. Steel stud attachment – Fastener must penetrate a minimum 3/8″ beyond steel for optimal
7. Wood stud attachment – Fastener must penetrate 1″ info wood stud or beyond plywood for
Q: Can Backer-On be used with backer board over plaster?
No, Backer-on screws are not designed to go through plaster.
Q: Can Rock-On and Backer-On screws go through steel studs?
Yes, Rock-On and Backer-On screws can be used in 26 to 22 light gauge steel.
Q: Are Rock-On and Backer-On screws approved for use in treated lumber?
No, Rock-On and Backer-On screws are not approved for use in treated lumber.
Q: Are Rock-On and Backer-On Screw ACQ approved?
No, Rock-On and Backer-On screws are not approved for ACQ.
Q: How many screws do I need to put into a sheet of cement board?
We recommend referring to the cement board manufacturers guidelines for screw pattern. In floor applications, screws should be placed every 8″”. You will use approximately 55 screws per 3′ x 5′ cement board and 91 screws per 4′ x 8′ cement board. In ceiling applications, screws should be placed every 6″”. You will use approximately 55 screws per 3′ x 5′ cement board and 150 screws per 4′ x 8′ cement board. In wall applications, screws should be placed every 8″” when connecting to the wall studs. This will amount to roughly 25 screws per 3′ x 5′ cement board.
Q: Can Rock-On and Backer-On screws be used on Hardiplank?
No, Rock-On and Backer-On screws are not approved for exterior applications.
Q: What is the Climaseal coating made of?
Epoxy based polymer coating over electro-zinc plating.
Q: Can Backer-On be substituted for Rock-On and vise versa?
Yes, they can be substituted, but will not achieve optimal performance. For optimal performance, it is recommended to use the screw with corresponding board material. Rock-On screws are designed for fiber-glass cement boards. Backer-On screws are designed for fiber cement boards.
Q: Can Rock-On or Backer-On be used in 3/16 steel?
No, Rock-On and Backer-On screws can be used in 26 to 22 light gauge steel.