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!

2 Answers 2


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.

  • I thought about putting it outside of the perimeter as you suggested but I am going to have a panel that is going to be roughly 16" long (to span across joists) by 8" wide with plenty of left over space. I figured it would be neater to have everything "self contained" in the panel. However, I didn't even think to just cut a big enough opening in the panel and just mount the box in the drywall. Sometimes you over-complicate things and miss the simple solutions. Thanks for your input!
    – Dino Z.
    Dec 27, 2013 at 15:25

Do not use MDF! it will sag over time from the weight of the projector. Any wood product is better than using MDF. You can mount the electrical box on a 2X block if needed to get it into the right spot, extend the face of the box to get near enough to the surface of the mounting material, the 1/4" you referred to earlier or closer, use a clock receptacle to hide a portion of the plug if you want to clean it up a bit. This will require an extra deep box. Cut the wood so that the receptacle plate covers the cut edges where the electric box passes through. Or create a little cubby that covers the projector and the electric box, obscuring the wiring, but make sure there is room for ventilation and heat loss.

You may be able to get away with MDF, I have not had good experiences with it. It has its place, just not for support/structural. Saggy bookshelves come to mind.....

  • I mentioned MDF because I have left overs from another project. It's 3/4" thick and seems pretty rigid. I find it really messy to work with especially when have to do any router work with it. I also have 3/4" pine that I can use. The other option is to use a piece of oak. I know that should be more than stiff and strong enough!
    – Dino Z.
    Dec 28, 2013 at 13:41
  • Pine would do more than well for your project. The grain may show through your paint, oak would too, but not as radical. A little point up with putty on the bench before it goes up will smooth it out, then putty the screw holes, touch up the screw holes with primer, then give everything the final coat or two.
    – Jack
    Dec 28, 2013 at 13:53

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