Q: We’re remodeling our kitchen and adding an island. We’d like it to have electrical outlets, but the floor is solid wood over a concrete slab. How do we route wires through concrete without wrecking the floor?—Erica Venaski, Miller Place, NY
Just so you know, having a receptacle on a kitchen island is not optional; it’s actually required by the National Electrical Code on any island with a countertop bigger than 12-by-24 inches. Your wish is their command.
Running electricity to your island shouldn’t be too difficult, especially if you’re taking out the existing cabinets. And it will only require removing a strip or two of flooring. If you have scraps left over from when the floor was installed, I doubt you’ll be able to tell that any work has been done.
How to Run Electricity to a Kitchen Island
Why It Matters: In a recent This Old House project, homeowner Katie explained the frustration of having a big kitchen island with no electrical outlets: “When we go to get out the mixer to make cookies, we can’t plug it in or doing work, we have no place to plug in.” Even in relatively recent kitchen remodels, island receptacles are sometimes overlooked — but they should have been required at the time of construction. Adding one now is well worth the effort.
- You’ll have to cut a trench in the concrete for a PVC conduit, which will carry the electrical cable under the floor. The best spot for that trench will be underneath a flooring strip that runs perpendicular from the nearest wall to the spot where your island will be.
- Cover the neighboring strips with painter’s tape to protect their finish, then run a circular saw lengthwise down the middle of the strip.
- Make a second cut ½ inch away and parallel to the first; use a chisel and hammer to remove the three scrap pieces.
- Next, cut out the exposed strip of plywood or OSB that covers the slab, but don’t go all the way through; the concrete will ruin your saw blade. Instead, finish the cut with a utility knife. Save the piece for later.
- The next step is to rent an electric concrete-cutting saw with a dry-cut diamond blade. Use it to make four parallel kerfs about ½ inch apart in the exposed concrete. These cuts will kick up clouds of dust, so be sure to wear safety glasses and a dust mask. Having a helper hold a wet/dry vac hose next to the blade will help capture some of the cloud.
Pro Tip: When burying electrical conduit in concrete or underground, always call the utility locating service before cutting or digging to check for any existing underground pipes or wires. As one This Old House electrician emphasized during a project: “Before we do any digging, I call the utility locating service to check for any underground pipes or wires.” Even inside a home’s slab, older construction may have embedded plumbing or radiant heating lines that you don’t want to hit with a concrete saw.
- Continue making shallow passes down each kerf until they are all at least 2 inches deep. Then break off the tongues of concrete by knocking them sideways with a hammer.
- Vacuum the debris out of the trench, then lay in a length of 1-inch-diameter PVC conduit with a 90-degree bell-end elbow on each end. That diameter allows you the option of running up to three cables to your island if you, or a future owner, decide to install appliances there.
- To fill the trench, dampen it with water, mix a portland-cement grout, such as Quikrete’s Non-Shrink Precision Grout, to a pourable consistency, put it into the trench, and trowel it flush with the slab.
- Twenty-four hours later, take the strip of subfloor you cut out earlier, spread a moisture-cure construction adhesive over its bottom side, and stick the subfloor to the slab.
- Now you can glue a strip of replacement flooring to the subfloor. But first, cut off the tag of wood just below the strip’s groove. That will allow you to insert the strip’s tongue in the groove of the neighboring strip and fit the replacement flush with the existing floor.
Fishing the Wires: Once your conduit is set in the trench with the grout cured, you’ll need to pull wires through it. Feed an electrician’s fish tape into the conduit from one end and push it through until it emerges at the other. Use electrician’s tape to attach your black, white, and green 14-gauge stranded copper wires to the fish tape, then pull them through the conduit in one smooth motion.
Shown: Whenever an island is installed in a kitchen, code requires that it be equipped with at least one receptacle. For most islands, two is preferable.
