Lighting, Light Fixtures, Ceiling and Exhaust Fans - Max weight for octagon light box

I have a chandelier that probably weighs 35 lbs, and I am a little afraid of hanging this from the light box? The box appears to be attached to joist - but I don't know how much it will hold.

Any ideas on what the weight limit is for a ceiling light before additional support is required?

Thanks,
Derek

If the box is metal, then probably okay. If the box is plastic, then probably not okay.

National Electric Code (1999):

"410-16 (a) Means of Support - Outlet Boxes. Fixtures greater than 50 pounds cannot be supported by a fixture box unless the box has been listed for a heavier load."

The code is written in a circuitous and arcane fashion, but what they are saying here is that if you have a "fixture box", you can hang up to 50 pounds from it.

What makes a fixture box different from any other kind of box? The size of the screw threads mainly - that and the way the manufacturer makes it so it will handle a 50 pound load. A fixture box will have # 8 screw threads. If yours does, your chandelier should be OK hanging from it. Manufacturers make their fixture boxes to comply with this requirement in the NEC.

If you want an extra margin of safety, install a fan rated box. They have #10 screw threads and are generally rated to support 75 pounds.

If a box has #6 screw threads it is not a fixture box and you are limited to no more than 6 pounds.

Thanks for the help guys - I checked the box out and it was metal, and then found the weight of the chandelier out exactly (it was a little less than 30 lbs).

So the light is hanging in my kitchen presently - and hopefully it will stay!

Thanks again!

Derek