How to Locate a Hidden Electrical Box Behind Metal Siding During Installation

Installing metal siding on the inside of a barn or workshop is usually a fast, simple process. However, encountering the need to accommodate for electrical boxes, such as those used for outlets, switches and panels, can be tricky. It's difficult to know the exact location of the boxes behind the siding and cutting through it blindly can ruin an entire piece if you make a mistake.

However, by using an ordinary tube of lipstick, you can make accurate marks that will help you know exactly where to cut. Lipstick is the perfect choice for this role because of its high visibility, non-toxic composition and easy-to-clean characteristics. Below is how you do it:

Tools and materials needed

  • Tube of lipstick in any bright color
  • Electric drill with ¼-inch drill bit
  • Portable jigsaw with sheet metal-cutting blade
  • Metal file
  • Leather work gloves
  • Shop towel or cloth

Step-by-step procedure

1. Partially install the siding—Whenever you approach an electrical box, go ahead and install the piece of siding over the box as if you were going to cover it up. However, instead of using a full number of screws, install the siding using only one screw; drive the screw in a location as close as possible to the center of the sheet. This will provide you with a balanced, temporary fitting for the next step.

2. Pull back the siding that covers the electrical box—After screwing the siding, ask a helper to hold the siding in place so that it doesn't slip or move out of position. Grasp the edge of the siding closest to the electrical box that lies underneath, and pull it back to expose the box. Be sure to wear leather work gloves while handling the siding in this manner so you don't cut your fingers or hands. In addition, be careful not to pull the siding too far back to avoid creasing it.

3. Mark the electrical box with lipstick—Once the electrical box has been exposed, ask your helper to help you keep the siding pulled back out of the way. With the tube of lipstick, generously mark the facing edge of the electrical box so that it is completely coated.

4. Transfer the tracing to the siding—After marking the electrical box, slowly lower the siding back into position over the box. Be sure the siding is still in its proper position, and don't let it slam against the electrical box. Next, firmly push into the siding in the vicinity of the still-hidden electrical box, and rub around in a circular motion with the palm of your hand.

5. Remove the siding—As you finish transferring the tracing to the siding, remove the single screw holding it in place to the framing and gently lower it to the ground. Pull the siding away from the wall carefully so that you don't smear the lipstick marks.

6. Cut out the electrical box tracing on the siding—With the siding in a safe, steady location, locate the tracing on the siding you made above in step 4. If you performed the tracing successfully, there should be a colored outline of the electrical box on the siding.

Drill ¼-inch holes at each of the corners of the electrical box; be sure to keep the holes inside the trace lines with only the outer edges of the holes lying flush with the tracing lines. After drilling the holes, insert a portable jigsaw with a sheet metal-cutting blade into one of the holes and begin cutting along the tracing lines. At every corner hole, reposition the saw so the blade aligns with the 90 degree change in tracing lines.

7. Reinstall the siding—Once the tracing is cut away from the siding, remove the cut-out from the siding and discard it. Use a metal file to remove sharp or rough edges, and wipe away the lipstick residue from the siding with a shop towel. You can use the same towel to remove lipstick from the electrical box. Once the lipstick is removed, proceed to reinstall the siding as you did in step one, but this time continue to add all fasteners until the section is firmly secured.