I'm in the process of adding a floor to our basement, using the Building Science recommendations (1" of foam insulation covered by 2 layers of 15/32" plywood, covered by some sort of playroom flooring. I'd like to at least have the option of running power to the center of the room in the future, so I was thinking of running some ENT under the plywood, but not actually wiring anything. However, I'm not sure what sort of receptacle would be appropriate, eventually, and if I should put a box in place for the future.

I can find two types of boxes that are rated for floors, and neither seem appropriate in this case. One type is specifically for installing into wood floors, assuming you have access to the floor from below, and the other type assumes that you're pouring concrete and will be pouring the box around the concrete. Both are far deeper than I'd be able to fit anyway without chiseling out some concrete, and even then the openings for conduit are placed in such a way hat I'd have to chisel out even more concrete.

Am I missing something here, or is adding a floor receptacle to an already existing foundation not realistic?

2 Answers 2


I have put in quite a few concrete rated boxes, I like metal over the plastic ones and conduit is the way to go. If you want data there are cover plates for that and of corse the power receptacles. There are larger boxes but I usually recommend deep single gang because the proper cover plates are “reasonable” with that said a deep single gang box rated for concrete 30-40$ with a brass cover with 2 screw or flip up covers (I prefer screws as the flip up covers break).

When I set boxes in concrete I usually use a chunk of styrofoam inside the box and cover the opening with duct tape 2-3 layers, I use rigid conduit and tie the box /conduit to the rebar. When finishing I make sure I work the cream enough I can see the outline of the box just below the surface. Once the concrete is set it is easy to chip the thin surface coat of concrete. If the box is slightly recessed it won’t be a problem code wise but be careful when clearing the green concrete from the screw tabs (the concrete is easy to cut just after set but not fully cured)

If you let the concrete fully cure it is still not difficult to open a box that is sealed. Start in the center and chip it up with a hammer and chisel, as you get to the end of the box use light sideways blows not in the center at the ends you don’t want to damage the tabs the screws thread into usually a tap on either side and then pull up on the tape will break enough to expose the tabs. Remove the styrofoam and any concrete that might have leaked into the box (this is why I recommend a styrofoam block to fill the box just in case.

Now you can pull your wire and install the device and cover plate. My last house I put in power for my theater seats and another for an air hockey table, if I did it again I would have dedicated 1 box at the seating area for wired surround sound as the wireless ones were a PITB.

  • I don’t think I explained the problem well. This is for a foundation that was poured 20 years ago. I’m trying to figure out a way that doesn’t involve destroying part of the floor to make room. Mar 15, 2020 at 18:14
  • Trenching a slot and using rated MC with the internal liner only requiring 3/8 may be the way to go with a retrofit. Smaller than 1/2” conduit but a old work box listed for concrete mortared in place with a brass cover plate would be my plan for power, if data flex non metallic would be fine but I still suggest metal because when plastic tabs strips out it stinks but metal can be reformed.
    – Ed Beal
    Mar 16, 2020 at 2:10

Será necesario de igual forma cinselar el ormigon, o lo más recomendable sería aumentar el espesor del piso de madera con algunas capas de hule espuma o lo más conveniente "corcho"ya que aún que cincel es el piso deberás dejar un canal desde el registro eléctrico hasta el lugar que deseas poner el receptáculo para pasar la manguera del cableado..

Google Translate / Edit

It will also be necessary to chisel the concrete, or the most advisable would be to increase the thickness of the wooden floor with some layers of foam rubber or the most convenient "cork". Even though you chisel in the floor, you must leave a channel from the electrical source junction to the place you want to put the receptacle to pass the wiring. .

  • 1
    Welcome to DIY Home Improvement. This is the second instance of your answer being in Spanish. Please post your answers in English which is the preferred language on the site.
    – Michael Karas
    Mar 15, 2020 at 11:53

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