I am updating a light fixture. It appears to be a 4 inch rounded square 1 1/4 inch box in the ceiling sticking out about 3/4 of an inch.
This will not work with the new fixture and bracket. Will a 4 inch round shallow box fit? I bought one but I'm doubting it is going in that easily.
I see there is also a 3 1/2 inch round shallow box I could get. I assume that would fit, but the mounting bracket appears to have 2 sets of holes. Are the common sizes 4 inch and 3 1/2 inch?

electrical box

  • 1
    Take the mounting bracket to the store and you can try to attach it to the box before you buy it.
    – jay613
    Jan 9, 2023 at 15:47
  • The issue is the box is sticking out of the ceiling, I got another box that will be flush with the ceiling but those boxes are all round and as you can see, this box isn't round. Both are 4 inch, but when holding them up to each other in the store, the 4 inch round seems a little bigger so I"m trying to figure out from people that have done this before.
    – robl45
    Jan 9, 2023 at 15:54
  • 3-1/2" is not a common size and is poorly supported by lamps. I would not use it except for repair-in-kind. Jan 9, 2023 at 22:21
  • @robl45 -- does the lamp not fit correctly with the box sticking out, or is it merely an aesthetic issue? Jan 10, 2023 at 4:15
  • If you have a flush-mount fixture you're probably gonna need a medallion of some sort.
    – Huesmann
    Jan 10, 2023 at 14:38

2 Answers 2


That's called an "octagon" box (note the 8 sides, even though they're not equal sides), and usually they don't stick out of the ceiling like that. If this is the way the box has been, without a cover over it of any sort, that's a code violation. It's too easy for something to get stuck in there (even on the ceiling) and the person holding the thing to get electrocuted.

Normally, there would be a decorative "rose" or "cover" provided with a ceiling lamp that is designed to hide the inside of the box.

If your "updated" light fixture did not come with a cover of any sort, at a minimum, you can get a octagon blank cover plate like this one:

enter image description here
Source: Lowes.com. No affiliation or recommendation implied or intended

You'll note that this one even has a knockout in the center that you can remove before sliding it over the center post holding your light in place and tightening it up with the nut that's there. You could, if you desired, spray paint the cover plate white before installing to make it less noticeable up there on the ceiling.

This is an example of a pendant light (like what you appear to have hanging in your pic, but with a down rod instead of chain), with an arrow pointing to the "rose" that should cover the box that you have. You'll have to ensure that your new light has a large enough rose to cover that 4" octagon box, but, since that's a fairly standard size, that shouldn't be a problem.

enter image description here
Source: Lowes.com, specifically this.

  • I think that's what the problem is. The cover that came with the new lamp isn't deep enough to cover the existing box and meet the ceiling surface because the box is sticking out too far.
    – gnicko
    Jan 9, 2023 at 16:39
  • Yes, that is the problem, So I"m asking instead of the 4 inch octagon, will the 4 inch round 1/2 inch deep box fit.
    – robl45
    Jan 9, 2023 at 16:53
  • 2
    Octagon boxes come in different depths too, @robl45. Be aware, though, that replacing the box in the ceiling (especially if the box there is a new work box that's nailed into a ceiling rafter) isn't a 15-minute task, and will likely require removal of some drywall from the ceiling with subsequent patching and attempting to match the ceiling texture.
    – FreeMan
    Jan 9, 2023 at 16:56
  • 1
    You might consider simply leaving the gap (depending on how bit it is) or coming up with another method of hiding it (such as a strip of thin metal, bent to fit inside the cover) of the same color/finish as the lamp's cover to span the gap from the cover to the ceiling.
    – FreeMan
    Jan 9, 2023 at 16:57
  • Or a circle of wood, dished on one side so it can go over the box but be flat at the edges, drilled through so you can mount the lamp/cover against that. Or if you really want to get fancy, this might be an excuse to install a ceiling rose...
    – keshlam
    Jan 10, 2023 at 0:02

If you are comfortable with a bit of work, you can take out the octagon box and replace it with a 4 inch shallow 1/2 inch deep, "pancake" box. You may have to trim some drywall back, but it should be minor and will be hidden by the cover of the new fixture.

Be sure the circuit is off. Use the proper screws to mount the new box. Take a picture of the wiring before removal, but it is simple black/black white/white, ground/ground.

  • This is what I wanted to confirm. Thanks.
    – robl45
    Jan 9, 2023 at 19:23
  • 1
    If the current box is nailed into a ceiling rafter, I wouldn't consider the drywall work "minor". I've used an oscillating saw to cut new work plastic boxes out of walls and ceilings. Cutting through a steel new work box to remove it (because it's been nailed in) is going to be quite difficult and will likely require removal of a good portion of ceiling to get to the nails to pull them.
    – FreeMan
    Jan 10, 2023 at 12:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.