Built-In Bookcase: A Box Extender for My Outlet


My bookcases are being built on a wall with two existing outlets, which I would like to keep.  This is not a hard project, it just requires some power tools :) and…

a box extender which you can get at the hardware store.

A Box Extender fits over your current electrical box and “extends” it from as little as 1/8” up to 1-1/2”, so it is a must if you want to put in a new wall over an old one, or build in cabinets or bookcases.

Here’s how I did it:

Before you start, turn off the power to that outlet (and test that it is off).  I have a handy label inside my fuse box that lets me know what each of the switches controls.

1.  Measure.

Measure from neighboring cabinet or the wall, and the bookcase base or floor to the center of the outlet.  Then measure from the edges of the case and mark that spot on the cabinet back.

2. Cut your opening.

Move the case away from the wall, and cut or drill a small hole over your mark to check the accuracy.  If the hole lines up over the outlet when you put the case back, you can roughly enlarge the hole to half the width and height of your electrical box.

Do this with a Dremel Multi-Max, a jigsaw or reciprocating saw.


Once the hole is larger, you can determine the precise cuts you want to make to exactly line up with the outlet, and mark or draw those lines on your cabinet before cutting.  Move the cabinet away again, make the cuts and re-check the alignment.


3.  Remove the outlet from the electrical box.

This outlet looks like it is daisy-chained with the neighboring outlet, so it has 4 wires (plus the ground) attached to it.  Some outlets will only have 2 wires (and ground).  I moved the cabinet away again, and then I unscrewed all the wires going to the outlet, keeping careful track of which goes where, so I can put it back together safely.

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4.  Install the box extender.

I moved my cabinet back in place again (for the last time, so I made sure you are ready to leave it there ;), and placed the box extender over the hole I cut and over the original electrical box.


5.  Reattach the outlet.

Then I screwed the wires back onto the outlet, and screwed the outlet back into the electrical box and the extender.  The extender will come with extra long bolts to make this easier to do with the deeper box.   (However, if you need to buy longer bolts for this, the standard size for the bolts on electrical boxes is #6-32.) 


6.  Reattach the cover.

If your cuts were a little too big, or you slipped and accidentally scratched or cut your backing (and paint won’t cover), you can buy an oversized outlet cover to hide your boo-boo. 


Outlet covers come in multiple sizes. 



Don’t forget to turn the power back on when you are done :)

Whatever you do, don’t just build your bookcase in front of the outlet, hiding it back there.   It is illegal and dangerous to place permanent furniture (cabinets, built-ins, etc) in front of an outlet blocking it.  They need to be accessible by electricians, inspectors, the fire department, future home owners.  Never permanently “hide” an electrical outlet where you can’t get to it.

It is easy to build your bookcase keeping the original outlets in place… just use a box extender!

I’m starting to get ready to finally finish these bookcases!  Yay!  I still have some posts coming up though, so stay tuned!

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