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Can I Use Any Slot Cutter on Trex Decking?

Renee Miller

Trex decking is made from a mixture of polyethylene and wood fiber, which makes for a moisture-resistant and durable decking material. It will not crack due to expansion and contraction because Trex boards don’t absorb moisture as wood does. Although the two materials are different, Trex decking can be cut and fastened just like wood. However, when slotting Trex decking, your choice in slot cutter bits can affect the overall quality of your finished deck.

Why Trex Decking Requires Slots

When installing Trex decking boards, you have the option of using a hidden fastener system, which enables you to build a solid, sturdy deck without having to use visible fasteners. To do this, Trex boards must be fastened with a clip that fits into slots on the sides of each board. The clip is then fastened to the joists beneath the decking. Not all Trex boards are pre-slotted for these clips, and you may have to cut a board to fit a particular space and remove the slotted end. To fasten a board without having to drill screws through the top of it, you’ll have to cut a slot, or notch, into the side of the board.

Not All Slot Cutters Will Do

When slotting Trex decking, the slots must be spaced along the board so they occur at the joist locations. The slots must also be at the right height for the clip to fit into the board so that the fastening screws reach the joist. The corners of some Trex boards are rounded, which can cause problems with regular slot cutter bits by interfering with the bearing on the bit. This can cause the router’s base plate to lift from the decking, which will result in uneven slots or slots that are cut too high or too low. When this happens, the deck boards won’t be properly fastened to the joists. For this reason, Trex does not recommend using just any slot cutter when working with its deck boards. Although you can use a TC-G slot cutter for some types of Trex decking, it is not designed for use with boards that are thicker than 1 inch. Trex manufactures its own bit for this purpose. The Trex Hideaway Hidden Fastener slot cutting bit fits into most handheld routers and is exclusively designed for use with Trex decking.


Trex decking can be cut just like wood, but Trex recommends using only carbide-tipped blades and bits for this purpose. Although the size of blade necessary may vary, blades that have fewer teeth usually provide the best cutting for Trex decking boards. For example, Trex recommends using a 7 1/4-inch circular saw blade with no more than 18 to 24 teeth or a 10- to 12-inch blade with 40 teeth or less. Although Trex decking doesn’t split or crack, you need to cut it slowly to avoid uneven edges.

Rails and Balusters

Although you can use a router on Trex deck boards, the balusters and rail posts should not be routed, slotted or notched. Doing this can change the surface of these components, which will alter the durability of the rails and posts. In many cases this alteration can pose a safety risk as the railing system may not be as strong as it should be. Trex warns that routing, slotting or notching balusters and rails can void the warranty on these components.