Electrical – How should I mount a rework box if it has to go through an MDF/wood panel and drywall

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I need to install a combination power and low voltage box in the ceiling of my finished basement for my home theater projector. I can't bolt the projector mount directly to the studs because of alignment issues so I have to first install a 3/4" MDF or wood panel across the joists on top of the drywall. The projector mount will then be attached to the panel which will have plenty of space available for me to add the required rework box.

My question is, should the rework box be installed through the panel and the drywall or should it be attached to the drywall with a simple cutout through the panel? I believe code says that the box can be no deeper than 1/4" from the surface so I may already have my answer. I'm in Canada so I'm not sure if code is different here. Also, I'm not sure if there is an issue installing the box in MDF to begin with. I can always go with a piece of oak or pine.

Any guidance would be appreciated! Thanks!

Best Answer

Why does it need to mount in the MDF? Just put box outside the perimeter of the MDF.

But if you insist:

From my experience, the simplest and cleanest way to do this is to mount the box in the drywall. You can either put a box extender in the MDF, or cut a hole big enough to clear the whole faceplate. I typically prefer cutting a big hole for the faceplate because it results in a cleaner look by helping to hide the connectors.

First cut your MDF to size. Then cut a hole for the box in the MDF. You can either make the hole the right size to fit the extender, or you can make the hole big enough to fit the faceplate.

Hold the MDF in place or temporarily mount it to your ceiling. Trace the cutout in the MDF on to the ceiling. Remove the MDF, cut the drywall, and install your box.