Hi, I have no help on the question but it might help to get the correct experts to respond by adding something like, "wiring advice needed" to the title of your post.

@tozmo1 thank you! I’ll edit 😊

Fan rated means that the box can hold something as heavy as a fan, but they come in different configurations because of the space above the fan. If there is no space above, like if it's a concrete ceiling or there is HVAC equipment up there, then a pancake box may be used, but splicing can be difficult or impossible. If there is a single joist above, the original box may be a fan rated pancake but it could probably be replaced by a "saddle box" which has space for splices. If the joist is double or triple thick then the fan location may have to be moved to get clear headroom for a box that can accommodate splicing. If the space above is a void that is 6 inches tall, the original builder still may have used a pancake which may have to be replaced because of the need for wiring space.

He may have meant that you need a fixture with a different canopy for wiring space than the one in the picture, and he might have arrived at that conclusion after exploring the space above the fixture.

Is there an existing light that was hanging there? If you can, post a picture of the box in the ceiling.

I have a old house and same happened to me. Electrician went into attic and changed out the box. It was a pain, but he did it.

Yes, you can mod most boxes, but the old fan boxes you really can’t, due to rod it has sticking out.

Let's not throw the electrician under the bus just yet.

As @elltow points out it could be a pancake fan box issue that doesn't have the box volume. We also don't know if the power comes into the fixture box or into the switch. Is it a 2 way or 3 way setup. Lots of variables that might be coming into play

It also looks like the OP's chosen fixture might have a smaller than diameter escutcheon plate at the ceiling.

A picture from below of the ceiling box will go a long way to providing the OP better advice other than just get a new electrician.

Iffy, That chandelier don't look that heavy, plus the pancake box would be easy to change IF needed. Yes ask your electrical guy this and don't let him over power you!

Ken

Thank you all so much for the great feedback!! Our home was built in 2017, and there was no previous light fixture there. I am having someone take a second look tomorrow and I can post what it looks like inside the box when he opens it, but here are some photos from the outside. One photo is up close, and one is farther away so you can see the size scale. Thank you again- you guys are awesome!

So I'll guess the house was built with this box in place so that the buyers could install a fan if they wished.

You'll have to take that plate off in order to see how large the box is, and how it is anchored. The fan boxes I've seen are usually rated for several (like 70) pounds of weight, more than a standard light fixture. They are also heavier made in order to handle the torque of the fan motor. Mounting can be directly to a floor (or ceiling) joist, metal bracing bar rated for the weight, or a 2x4 nailed between the joists.

Inside:

It’s hard to tell. Does the box sit flush with ceiling? You will need to remove box and put a new one in most likely. Do you have an active? All you need is one that pops in a little larger than current hole. Sorry but I’m surprised your electrician couldn’t figure this out. I could do this myself.

Attic

That box is fine and there would be no volume issues. It is a pancake box but all you have is coming in is the hot (black), neutral (white), and ground (green or copper) so you're fine. No new box should be necessary. I'd also wager that that pancake box is screwed directly to a joist.

Looking back at your original post, you mention "plates"? Hmm . . . it makes me wonder if your fixture has non-standard mounting holes - holes that are too far apart or too close together than the standard . There are a variety of mounting brackets or plates that would attach to the existing box from which to hang your chandelier. Google "fixture mounting brackets".

I recently ran into that situation with a light fixture from Rejuvenation that I bought off Craigslist for $10. It was a steal. Unfortunately, when they took it down, they didn't save the mounting bracket and the mounting holes were not a standard width apart. I solved it by combining two different mounting brackets.

I used what I had on hand. To show you what I'm talking about, here's what I did.

First I cut one type of mounting bracket in half:

Then I mounted the cut pieces to another type of mounting bracket:

I aligned the "extensions" with the fixture mounting holes:

Then I mounted the bracket to the electrical box and hung the fixture. Not bad for $10.

Maybe I'm just not used to modern fixtures, but that chandelier's canopy looks odd to me. Was it sold by a standard lighting supplier? Is it intended for US use? Did you by any chance direct-import it, or buy it from an Asian or European supplier via one of the big online places?

I agree, it does look odd.

ttjl04 - Any chance of a close up picture of the top your light?

Well, after all that I will tell you that box is normal as they come, its a standard pancake box. What appears to be less normal is the canopy (mounting plate) for your new fixture, looks as tho it may be a Euro sized canopy, or closer to a 3.0 size rather than our standard 4.0 size .......I would like to see the hardware that came with your fixture. Pancake boxes are just more shallow, otherwise, they are standard issue for mounting, and most of all ...........THIS HAS NOTHING TO DO WITH A FAN.

If i was you i would go to a lighting store or a hardware store and buy a chrome canopy kit and use it in place of the one that came with it.