Plastic boxes breaking

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Cjhaddenjr

New User
Location
Duncan sc
Ran into an issue at my daughters house, which was built in 2000 that I've never seen before and wondering if anyone else has seen this problem too. She had two light fixtures that were hanging from twelve foot ceilings by chain. On both the decorative covers were not up next to the sheet rock so I got up and started to tighten the first one and realized one side of the blue plastic box where the mounting screws go had broken off. After getting in the attic, I saw where the joist where the box was nailed on had twisted and pulled the box upward and the decorative cover had kept it from going up, therefore breaking the box. Is this an isolated incident or has others seen it before? The one fixture over the dining room table was at least 25 pounds and a lot of glass to it and hanging by only one screw in a plastic box was an accident waiting to happen. I replaced both with metal boxes.
 

SceneryDriver

Senior Member
Location
NJ
Occupation
Electrical and Automation Designer
Pretty common occurrence I think. Screw holes for devices strip out too very easily. I loathe plastic boxes for that reason. I've seen them get brittle with age too; metal boxes don't fall to dust after 20 years.


SceneryDriver
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Pretty common occurrence I think. Screw holes for devices strip out too very easily. I loathe plastic boxes for that reason. I've seen them get brittle with age too; metal boxes don't fall to dust after 20 years.


SceneryDriver

I would second that,

What brand or type of plastic box where they?
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
...I saw where the joist where the box was nailed on had twisted and pulled the box upward...
That's not good either. It indicates that the rafters (joists are in floors) and therefore likely the entire house, was built with cheap "green" lumber, not kiln dried. If the house is not old, I would be getting it inspected for other defects and possibly going after the builder.

People use plastic boxes nailed to rafters for hanging fixtures? Sheesh...
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Seems like the lumber used may have been wet when it was installed. After curing it has a tendency to warp (I've even seen it warp just prior to the sheet rock installation going up). That's what the bridging between joists helps to prevent along with a strong-back (and possibly plywood flooring) across the joists in the attic does in addition. As a personal preference I choose not to use 4" round plastic boxes in cases like yours for just the reason you described. If you're in a small hallway with 8' ceilings that's a different story, plastic works fine.
 
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