How to Cut Holes for New Reheat Registers in the Floor

Locate the floor joists beneath the subfloor with the stud/joist finder. You can also look at the screws that have been drilled into the subfloor to determine where the floor joist is situated. Your new reheat register hole will need to be located on one side or another of a floor joist so that you can mount the register on the joist.

Mark the outer edge of the joist location with the pencil and tape measure. The width of joists is 2 inches, and subfloors are screwed into the center of the joist, so if you measure back out from the screws or the center of the joist one 1 inch, this is the outer side of the joist. Place your register upside down along this pencil line and scribe the outline with your pencil.

Set the depth of your circular saw to half an inch. Use the tape measure to guide the depth. Do this while the saw is unplugged. Plug the saw in. Hold the saw guide with your off hand and use the thumb of this hand to hold the guard for the blade open. Grasp the handle of the saw firmly in your main hand.

Slowly lower the blade of the saw into the plywood subfloor along your pencil marks. Overcut your marks by roughly a quarter of an inch, as the blade of the saw will not cut all the way through if you merely cut to the topside marks, as the blade’s curvature means the cuts slope away from the upper section and are actually shorter in length on the bottom side. Set the saw to the side when finished and tap the section out with your hand to clear the hole and make room for the register.