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I want to replace a light fixture in my house (1950s construction) with a ceiling fan. I doubt that the existing box will support a fan.existing ceiling box

I see the big screw in the middle of the box. Is it holding the box up? How difficult will replacing the box be without attic access?

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    The metal box itself is probably OK. It all depends on what it's fastened to and how. Is it fastened directly to a ceiling joist, or to a 2x4 that runs between two joists? And with what kind and how many fasteners.
    – SteveSh
    Jun 20 '20 at 23:54
  • I don't know what is holding it up. I guess there's no way to tell short of cutting out the ceiling around the box. Jun 21 '20 at 1:03
  • Don't hastily enlarge the hole without first trying to remove the existing box. With the box removed you should be able to see what you have to do from that point. Jun 21 '20 at 3:22
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If you have determined that the existing box is not sufficient to support a fan or you want to make sure that a box is designed for a ceiling fan, it would not be difficult. After opening the breaker to the box in question.

  1. Remove the old box. You may have to cut some of the drywall away to remove the old box and to install the support bracket of the new ceiling fan box.
  2. Once the old box is removed, use a ceiling fan mount like this and attach to two joists.
  3. Re-patch the sheetrock and mount the ceiling fan.
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  • Try to do this without tearing into the ceiling needing a drywall repair. A drywall repair would be a lot of work and then require matching texture and paint. If the box would need replacing there are ceiling fan boxes with a spanning bar that can be inserted through a hole the size of the existing one. Jun 21 '20 at 0:43
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    Ceiling fan box installable through hole (called old work ceiling fan box) lowes.com/pd/… Jun 21 '20 at 0:51
  • Thanks for the link to the old work ceiling fan box. My plan has been to use one of those, but I'm worried about the difficulty of getting the old box out. Jun 21 '20 at 1:05
  • I have never been able to remove the old box without cutting the sheet rock. I have use the ones that RBlum pointed to when installing for friends. Jun 21 '20 at 1:14
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To determine how the box is attached you should proceed to remove the box. First remove the flat bar with projecting machine screws. Then look at the inside of the box to see how the box is attached to either a metal bar or to a ceiling joist. If the latter, it should be readily removable without enlarging the hole.

I think removing the box will be easy. The harder part would be removing a bar, if the bar was installed as new work before the ceiling was put up. I can't think of any appealing way to do that.

The instructions for the new lighter Hunter fans allow installation into a ceiling joist with special wood screws provided if the box is attached to or near the joist. The light duty junction box is left in place and the large shroud covers the box.

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  • Often, the "bar" (if I'm thinking of the same thing you're thinking of) is attached to the back of the box and the pair are (or at least were) sold as a "ceiling fan box". The bar is the extra reinforcement required to allow the box to carry the extra weight and vibration of the fan. If the OP finds that, he should be fine, no?
    – FreeMan
    Jun 21 '20 at 16:41
  • Some very light duty boxes with a bar would not have a bar heavy enough to support a fan. In those the purpose of the bar is to allow positioning of the box between joists. Jun 22 '20 at 13:02
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I would seriously double that the existing box is fan worthy. That big screw in the middle leads me to believe the box is attached to a bracket bar of sort. Removing that screw/nut should allow the box to be pulled out after undoing all the wires (which you need to carefully mark so you can reinstall them in the new box. If there is a bar support, you'll have to cut it out with a hacksaw blade or rotary tool, like a Dremel, with a cutoff wheel. Then proceed to install you new old work box or box to joist. If you need to cut away some drywall around the box, there are cover plates available to cover up the additional drywall removed. They come in many sizes depending on how much you need to cut out. See picture below.

enter image description here

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A metal box in wood construction is usually attached by means of nails, or possibly screws, through ears attached to the box. It might look something like that shown below -- you can probably shine a light in through the gap between box and drywall to confirm whether yours matches.

new work octagon electrical box

If it does, the simplest thing to do is probably to cut the nail flanges off the box. You can do this manually with something like a hack saw, or using power tools such as a jig saw or reciprocating saw. You'll want to ensure that the electrical cables are clear of the saw blade. The cables entering the box are very likely to be out of harm's way, but it's possible there could be cables routed just above the box too. Figure out some way of confirming the area is clear. You might be able to see in there if the gap is large enough, but if not, you might be able to probe with a screwdriver, a piece of bent wire, or other tool.

After the box is detached from its mounting you'll be able to work the cables free of the box. Finally, install an old work ceiling fan mount as per its instructions. If the nail flanges from the original box aren't in the way of the new fan mount then can simply be left in place.

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