- Saddle box: A saddle box quite simply saddles over a ceiling joist and attaches directly to the joist. The biggest downfall of this type of box is that not much room exists within the box to coil up extra wiring from the fan. This box can be used for old work (remodeling) and new work (new construction). They are perfect for the unlikely occasion when the ceiling fan will be installed exactly where a joist is present.
- New work box: New work boxes are attached to a support bar that extends out in much the same manner as a shower curtain rod and attaches to both ceiling joists with nails. This box can even be used as a remodel box as long as you have access to the ceiling joists.
- Old work box: An old work box extends out just like a new work box. The difference between the two is that the old work box doesn’t nail into anything. It simply extends out and spreads out the weight of the fan over the drywall, plaster, or whatever else the ceiling may be made of. The advantage of an old work box is that all you need is a small hole in the ceiling to poke the bar through and then extend it out. You don’t need access to the ceiling joists.
Ceiling boxes are rated for various weights. Keep this in mind when choosing a box. With an old work box that attaches to nothing, keep in mind that if the box supports 70 pounds but your ceiling will only support 10 pounds, then your ceiling fan will probably end up on the floor.