I came home to find a ceiling light fixture hanging halfway to the floor and the glass dome shattered. For right now I re-attached the wires that had come loose but need to replace the fixture. Close inspection of the box showed that two screws had held a strap in place but that the plastic that they were threaded into inside the box had broken. I might be able to just get longer screws and use them to attach to the unbroken plastic but replacing the ceiling box altogether might be the best idea. Problem is I looked and looked and cannot figure out how the box is attached to the ceiling. I see no fasteners whatsoever. I see the wire cable coming down from above through some type of clamp, so that part looks easy. Unattaching and reattaching the box is my problem. How are these things usually attached. How easy are they to replace?
Depends but one common method is for the box to be nailed to one of the rafters - either directly or it’ll have a couple of telescoping metal rods (so you can fit it in place whether the rafters are 16 or 24 inches on center) that you extend so that they fit snug against the rafters, then each end is nailed into place.
Can you get up above the ceiling to check? That’ll be the easiest way to see exactly what you need and to replace it.
I’m not sure there’s enough information here to answer the question, and I’m not sure exactly why you want to replace the box…
I am assuming you are talking about an ordinary junction box from which a fixture is suspended, and into which electrical wires are routed.
Approximate dates your home was constructed might help a little; if it’s really old, all bets are off.
Ceiling juntion boxes are attached according to how much weight the box is going to have to bear. A typical box has side holes and top holes (assuming it’s being attached with the opening facing down; these holes are used for screws. If the box is being placed adjacent to a joist, the screws simply go into the ceiling joist; if between joists, then a supporting section of wood can be attached to each joist with the box either suspended from that support or attached at the side.
Boxes can also have metal strips on the side, usually adjustable, which run just above the drywall ceiling and engage the joists; both the drywall and the engaging ends help support the box.
For heavy fixtures–a chandelier, say, the box might have a really sturdy wooden support placed above the level of the ceiling joists; it’s hard to say.
For trivial fixtures, it’s possible the only support for the box is a section of light thinwall conduit; this is rigid enough for light work but very poor construction technique (as the only support for a junction box, b/c you don’t know what might be hung from the box down the road). The conduit itself has an end attachment which, from the inside of the box, has a small ring that screws on and secures it; not all wiring is done with conduit, so this is not necessarily your case.
A photo or two would be most helpful around exactly what has gone wrong. Most light (un-heavy) fixtures are supported by a small metal plate which is in turn attached to the junction box. That’s an easily available part. Vertical weight bearing of a fixture should not depend on screws into plastic…
Sounds like a plastic junction box. Which is not the proper type of box to hang a heavy object.
If it is, break it apart with a hammer and screwdriver. Or if it is held in with nails and a bracket get a hack blade and slide it between the side of the box and the stud, cut the nails.
Then get fan power box follow directions and moount it.
The house is twelve years old. I do not have access to the attic over the fixture. The reason I think I will need to repace the box is that it had a metal strap attached over the opening and the light fixture (which was inexpensive glass domed three bulbed) attached to this metal strap. The two screws which held the strap up were screwed into some type of heavy plastic (it looks and feels almost like bakelite) and the plastic with the screw holes broke, the screws came free, and boom. So I think I need to replace the box since the metal strap can no longer be attached.
I know exactly what you’re talking about. Being an electrician I’ve seen and mounted tons of these types of boxes. I’d bet the farm the box is simply mounted to the joist with two nails (supported to the box on the outside so you can’t see them). Now you have to use a fan rated box on all ceiling installations, but 12 years ago you could get away with a simple plastic box of the type you describe…unless a fan was intended to be hung there. Sounds like that’s not the case. Good thing too. The fan could have came down on someone. That’s exactly the reason fan boxes (heavy duty boxes) are required in all cases now.
First off make sure the power is off to the box. Just cause the switch is off doesn’t mean that there isn’t power at the box in all cases. Hard to say without being there, so turn off the circuit to be sure.
The box you need to replace can simply be pried loose from the joist with a large screw-driver placed between the stud and the box. Twist and turn and pry gently (not to wreck the drywall too much) until it either falls away from the joist or gets loose enough that you can take a side cutter and snip the nails. I wouldn’t use an electric tool or a saw to free the box in case there are other wires nearby that you might end up cutting. It’ll take a few minutes to remove the box with a screw-driver but it’s the safest way to do it.
Next, you need to get a fan rated box that’s intended to be installed as ‘old work’. That means it can be installed in an existing opening but you don’t have access to the joist as you would in new construction. It’ll typically come with a spreader bar that can be adjusted to catch both of the joists in the ceiling cavity, and be rated to support a fan and such. The box itself can be mounted anywhere along this spreader bar with the included clamp and bolt. This will typically also be a metal box so you won’t have to worry about the screws stripping out anymore. You’ll be able to re-use the parts from the fixture that came down, including the metal strap that came undone.
Most likely its held in place by two nails. Like this one http://www.lowes.com/lowes/lkn?action=productDetail&productId=70978-223-B520A&lpage=none.
Pressing up on it very hard can often break the nails from the brackets. In that case you force the box into the open space above. Pull the wires out of the box and the nails out of the joist. Leaving the old box in the ceiling would minimize drywall damage.
Another method is to use a saw blade between the box and the joist to cut the nails. Be careful doing this. Hitting the wires can make the project much harder. This also damages the drywall and may prevent using a lightweight old work box as the replacement.
If you have a lightweight fixture your attaching to this the easiest install would be a box like this http://www.lowes.com/lowes/lkn?action=productDetail&productId=70983-223-B618R-UPC&lpage=none It would fit back in the same hole. Turn a few screws and its done.
For heavier fixtures you would use a box of this design. http://www.lowes.com/lowes/lkn?action=productDetail&productId=73273-427-926&lpage=none You may not be able to put in in the exact same spot. The support bars often do not let you mount the box right next to the joist. It would end up an inch or two away from the existing hole. Though the base on most fixtures would cover that.