Electrical Boxes: Old Work vs. New Work, Metal vs. Plastic

  • 01 of 05

    Types of Electrical Boxes: Four Categories

    Electrical Wiring Roughed In
    Electrical Wiring Roughed In. Getty / Mattboy_Slim

    The world of electrical boxes can feel overwhelming in terms of sizes and materials and purposes. So for the beginning DIY electrician, it's helpful to break down types of electrical boxes into two areas--materials and installation types.

    It's a simplification, but simplifying electrical boxes in this manner goes a long way toward helping you understand all types of boxes.

    1. Materials: Plastic vs. Metal

    Metal boxes have been around for a long time. Metal boxes are generally used with metal-clad cable. Plastic boxes are easier for beginners to handle and can be cheaper. Generally use plastic boxes with plastic-clad (also known as Romex or NM) wiring.

    2. Type of Installation: New Work vs. Old Work

    The term new work (sometimes new construction) refers to walls that have not yet been closed in with wallboard. Because the framing is exposed, it is possible to nail or screw these new work electrical boxes to the sides of the studs.

    The term old work (sometimes old construction or retrofit) refers to walls that are already covered up, making it impossible to access the studs. Thus, old work electrical boxes attach directly to the wallboard.

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  • 02 of 05

    New Work (Construction) Plastic Box

    new work plastic electrical box
    (c) Lee Wallender; Licensed to About.com

    Electrical boxes composed of ASB plastic or fiberglass are used with NM wire.

    Besides low cost, another advantage of plastic boxes is that they are light and easy to handle.

    Buy on Amazon - Carlon New Work Boxes

    A disadvantage of nail-in plastic boxes is that, unless nailed carefully, they can warp, twist, or misalign. Additionally, the tabs in the back are supposed to partially punch out, acting as clamps. But these flimsy flappers are a sorry excuse for clamps.

    Learn how to install a nail-in, new work plastic electrical box perfectly without warping or misaligning.

    Continue to 3 of 5 below.
  • 03 of 05

    Old Work Plastic Box

    old work plastic electrical box
    (c) Lee Wallender; Licensed to About.com

    Old work plastic electrical boxes pop into wallboard cut-ins. The ubiquitous Carlon old work box shown here tightens in by means of "wings" with a screwdriver.

    It's not the most secure method of holding in a box. And, as we've pointed out, plastic boxes can be quite brittle. An errant swing of the hammer can shatter a plastic box, even though box manufacturers like to claim that their products are "shatter-proof."

    Of the four methods in this gallery, the old work plastic electrical box presents the greatest dichotomy: extremely cheap and easy to handle, yet flimsy and prone to breakage.

    Continue to 4 of 5 below.
  • 04 of 05

    New Work (New Construction) Metal Box

    new work metal electrical box
    (c) Lee Wallender; Licensed to About.com

    When you've got access into the wall, you'll have no better feeling of security than when you can screw in a metal new-work electrical box.

    This type of box will absolutely stay in place under any conditions. Metal new-work boxes often have built-in back clamps for holding down the wire.

    Tip: Should You Buy the "Adjustable" Kind?

    It's possible to purchase either metal and plastic new-work electrical boxes with a mechanism that adjusts the box in or out of the wall. The intention is to provide flexibility, so that the face of the box will come flush with the wallboard merely by turning a screw, rather than digging into the wall and reattaching. Sound like a good idea? It does to me, too, but I've never fallen in love with them. The adjusting mechanism never seems to work very well, and it makes the box as a whole less stable.

    Continue to 5 of 5 below.
  • 05 of 05

    Old Work (New Construction) Metal Box

    Old Work Metal Electrical Box
    Lee Wallender

    In the old-work box category, I recommend metal over plastic. Inserting old-work boxes into wallboard is a flimsy enough proposition; why compound the problem by going with plastic?

    Metal old work boxes tighten against the drywall by means of Madison straps.