Old work box for light fixture support?

[ritelec]

My understanding is that an old work box (metal or plastic) can be cut in to a ceiling or wall to support a device like switches, receptacles, and smoke alarms using the wall or ceiling surface for support. If installing an old work box to hang a fixture the box needs to be supported from a framing member.
I opened up a wall the other day to install a bar box for a wall sconce. Something in the back of my mind says you can use the wall (not framing member) for box support on wall mount fixtures to a certain weight limit. Am I right or wrong? Looking in 314.23 but not finding anything. looking in luminaires but seems to bring me back to 314. Any direction to locate if it's there?
Thank you

 

[Little Bill]

See 314.27
Mostly, it's determined by what the box is rated for and must be marked/stamped in the box.

We had a similar thread a while back that might lend some direction
https://forums.mikeholt.com/forum/a...l-forum/2540379-old-work-box-for-5-lb-fixture

 

[ritelec]

Thank you,
Read the link and 314.27. Not very clear or cut and dry.. "guessing" Lighting fixtures on ceiling go to framing member ( unless I get lazy and it looks like the box and ceiling material will support it). Wall (vertical) box also goes to framing member unless the fixture is 6 pounds or under and /or more weight if the box is rated for the weight and it looks like the wall will support it.