A Step by Step Guide to Installing Electrical Boxes in ICF Walls

icf-electrical-box

Professionals and DIYers both, can install electrical boxes into insulated concrete foam (ICF) walls. However, successful installation requires careful and precise techniques. The application must include prudent measuring for placement and cautious securing of the boxes. It is important that, after installation of the boxes, chases, and wires – and before moving on with the building project – a building inspector should confirm the code compliance of the boxes and wires.

The Purposes and Advantages of Electrical Boxes

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Electrical boxes (also called junction boxes) serve several essential purposes: 

  • Electrical boxes provide the means for securely mounting and organizing the electrical cables and devices (outlets, light fixtures, switches, etc.) in the ceilings and walls.
  • Electrical boxes enclose the wiring connections to protect people and neighboring materials from electricity. 
  • Electrical boxes also protect the wires from moisture and dust, stop small critters from chewing the wires, and prevent fires within the box from spreading. 

Types of Electrical Boxes

Electrical boxes come in a wide range of sizes and shapes in both plastic and metal. For safety and legality, builders must select the right size electrical box to prevent crowding too many wires and devices into a single box.

The Pros and Cons of Metal Electrical Boxes

Metal electrical boxes provide several benefits:

  • Excellent strength and durability
  • Ultraviolet (UV) stability
  • Flame resistance
  • Maintain their strength at both low and high temperatures

Unfortunately, metal electrical boxes come with several problems and risks:

  • Metal boxes cost more than plastic boxes.
  • Metal boxes weigh more than plastic boxes.
  • The conductivity of metal boxes requires grounding. 
  • Metal boxes can corrode.

The Pros and Cons of Plastic Electrical Boxes

Prairie ICF

Plastic electrical boxes provide a few advantages over metal boxes:

  • Plastic electrical boxes cost less than metal boxes.
  • Plastic boxes weigh less than metal boxes.
  • The non-conductivity of plastic eliminates the need for grounding.
  • Plastic boxes do not corrode.

However, plastic boxes come with several downsides:

  • Plastic boxes do not provide the strength of metal boxes.
  • Ceiling fans should not use plastic boxes.
  • The low fire- and UV-resistance of plastic boxes makes them less stable than metal boxes.   
  • Cold temperatures can make plastic boxes brittle.

A Step by Step Guide to Installing Electrical Boxes in ICF Walls

Tools and materials needed for installing electrical boxes in ICF:

  1. Electric boxes, anchor screws
  2. Sharpie
  3. 12-inch ruler
  4. A hot knife provides a means to quickly and effectively cut an opening in the ICF. A hand saw can do everything a hot knife can; it just takes more time.
  5. Electric chainsaw ( hastens the install of the electric boxes)
  6. Levering tool
  7. Hammer
  8. Chisel or crowbar
  9. Drill and masonry bit

Mounting a Plastic Electrical Box:

  1. Position the electric box flat against the ICF wall, next to a web, with the base of the box about 12 inches above the floor. With a sharpie, draw an outline around the box. 
  2. Insert the hot knife (or handsaw) along the marked line and begin cutting along the lines. Be sure to cut right up next to the web so that the flange  on the box can mount on the web. 
  3. Using a simple lever tool, pop the square of ICF out of the wall
  4. Check to see if any concrete sticks out near the interconnect inside the opening. To ensure the box lays flat, chip the concrete out using a hammer and chisel or crowbar.
  5. Slide the plastic electrical box into the opening, flush against the wall. 
  6. Attach the box’s flange to the ICF stud with anchor screws.

Mounting a Metal Electrical Box:

  1. Repeat steps 1-4 above, for mounting a plastic electrical box.
  2. To accommodate the chase running on either side of the electric box and make it easier for the electrician, remove the knock out (KO) rings on the two sides of the metal electric box. 
  3. Set the metal box in the opening.
  4. Using the drill and masonry bit, drill a hole in the back of the box.
  5. Insert a screw into the hole and secure the box to the wall

Cutting the Electrical Chase:

  1. A chainsaw makes it quick and easy to cut a chase. To avoid the webs, cut the chase from electrical box to electrical box along the interconnect.
  2. After cutting the chase, the installer can insert the electrical wire
  3. To secure the wire it in place, apply an expanding foam glue occasionally along the length of the wire.

Six Tips to Ensure Proper Installation of Electrical Boxes

The simplicity of installing electric boxes allows even DIYers to complete the work. However, several common errors can lead to unprofessional-looking installation that may not meet code requirements. 

  1. For a uniform look, install the electrical boxes at uniform heights. Building professionals often follow these standards when installing electrical boxes; 
    1. Install wall switches 40 inches above the floor,
    2. Place receptacle outlet boxes 12 inches above the floor, and
    3. Place outlets 4 inches above the floor.
  2. Place a spot of construction foam behind the plastic box before installing into the opening.
  3. Carefully screw or nail the flange of the plastic electrical box, perpendicular to the stud. Heavy swings of a hammer or sloppy application of screws risks pushing the box backward along the face of the stud. 
  4. To keep the box from twisting and deflecting during attachment, apply the screws or nails ¼ its length at a time, alternating back and forth between screws or nails.
  5. Before sealing the chase and electrical boxes behind sheetrock, hire a building inspector to ensure the code compliance of the boxes and wires. 
  6. To restore the insulative merit of the wall, fill the entire chase and gaps around the electrical boxes with low-expansion spray foam. Low-expansion spray foam doesn’t put much stress on the form so that it won’t make a mess. Once the foam is dry, you can remove the excess using a paint scraper or rasp.

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