Leviton Wallplate does not fit standard electrical box

Question

I pre-wired my house for a lot of low-voltage applications. I installed new-construction green plastic boxes of the appropriate sizes (e.g. 1-gang, 2-gang, etc.); at the time, I wasn't ready to finish, so I placed cheap blank wallplates over them - which fit perfectly.

Fast-forward, and I'm ready to complete the wiring. I bought a bunch of Leviton-brand wallplates with the "Decora" rectangular cutout, and several appropriate snap-ins for the cutouts. These Leviton things are sold everywhere - as far as I knew, they were a standard item.

Here's the problem: the spacing between the mounting holes on the green plastic low-voltage boxes is 3.25". The spacing between the screw holes on the Leviton plates are 3.75". Has anyone else run into this problem? Do I have to tear out the plastic boxes that are nailed into the studs and replace them with some special retrofit box? How do I make this work?

Answer 1

You don't screw a wall plate into the J-box (with the exception of blank plates). You screw it into the device that's mounted inside the box, and that device will have standard holes at the measurements you made. So if you have a GFCI outlet in there, the GFCI will be screwed into the J-box and then the wall plate is screwed into the GFCI.

Answer 2

I'm assuming you have the quick port inserts. Screw the inserts into the box first, then screw the plate to the insert. The plate you have should fit.