Securing troffers...

[emahler]

NJ related question, don't believe it's in the NEC....

we have a dropped ceiling installation with a mess of 2x4 troffers....must be independently supported, since we are never gonna get a piece of paper from anyone stating that the ceiling grid will hold it...

ceiling guys gave us 2 tie wire drops per fixture...

but the went to the bottom of the metal truss to support the ceiling, and the fixture...

i seem to remember that there was something requiring that the tie wire be secured to the top of the truss....

am i imagining something?

 

[acrwc10]

I've never heard that, metal trusses are pretty strong and T-bar isn't that heavy, compared to what a trusses rating is.

 

[Jim W in Tampa]

Here i am required to paint my grid wires and then i put the grid wire on the fixtures. Often i go 1 step further and put 4 screws from T into fixture. The concern is in event of a fire that they dont fall. Its a local issue and firechief issue.

 

[jusme123]

Here i am required to paint my grid wires and then i put the grid wire on the fixtures. Often i go 1 step further and put 4 screws from T into fixture. The concern is in event of a fire that they dont fall. Its a local issue and firechief issue.

Jim do you paint the whole wire or just 12" on each end to identify

 

[acrwc10]

Jim do you paint the whole wire or just 12" on each end to identify

The easiest way is to lay them out before they get installed and spray the whole bundle at once then install them. Let the paint dry first.

 

[sparky=t]

supporting from the top of the metal truss is usually a spec or building code issue that may require engineer / owner approval for bottom mounting.

 

[acrwc10]

supporting from the top of the metal truss is usually a spec or building code issue that may require engineer / owner approval for bottom mounting.

It would more likely be the other way around, if you couldn't hang it from the bottom it would be an engineers requirement or a requirement of the truss manufacturer. It is not in the building code.

 

[lakee911]

supporting from the top of the metal truss is usually a spec or building code issue that may require engineer / owner approval for bottom mounting.

Agreed. Better to check and be on the safe side.

It would more likely be the other way around, if you couldn't hang it from the bottom it would be an engineers requirement or a requirement of the truss manufacturer. It is not in the building code.

It might be there too, but generally they're loaded from the top.

 

[dirty steve]

I've heard that it was for fire safety when they are clearing the ceiling but later on I also was told it was for meeting seismic requirements in case of an earthquake and on some jobs we've had to do all four corners.

 

[billsnuff]

check the siesmic map and your local codes

http://www.disastercenter.com/build/seismic.htm

 

[acrwc10]

check the siesmic map and your local codes

http://www.disastercenter.com/build/seismic.htm

Seismic design category's are "a" thru "f" and are site specific. There are several factors taken into account in designating a seismic design category like what the soil conditions are, location to a fault, etc. They are clarified in the IBC.

 

[JES2727]

NJ related question, don't believe it's in the NEC....

we have a dropped ceiling installation with a mess of 2x4 troffers....must be independently supported, since we are never gonna get a piece of paper from anyone stating that the ceiling grid will hold it...

ceiling guys gave us 2 tie wire drops per fixture...

but the went to the bottom of the metal truss to support the ceiling, and the fixture...

i seem to remember that there was something requiring that the tie wire be secured to the top of the truss....

am i imagining something?

emahler,
You're not imagining it. It was explained to me by a building inspector as I was beginning a project several years ago. I was told it was in the IBC. The reason being that the bar joist is connected to the main I-beam only at the top. The bottom flange doesn't go anywhere, it just hangs from the top flange.

 

[acrwc10]

emahler,
You're not imagining it. It was explained to me by a building inspector as I was beginning a project several years ago. I was told it was in the IBC. The reason being that the bar joist is connected to the main I-beam only at the top. The bottom flange doesn't go anywhere, it just hangs from the top flange.

There is a lot more going on there then the bottom flange "just hangs from the top flange" do a search on trusses, I think you will be amazed at the way they work. "Tension and compression" the members act and react in ways that are not so obvious, but it is cool to follow the way they transfer load.

 

[jckenner]

There should be no logical reason for a general requirement not to attach troffers or grid to the bottom chord of any metal truss I've ever seen. (Not that logic always governs...) The weight is insignificant. I know CA (seismic) codes are reasonably stringent, and don't prevail in other parts of the country, but see the attached details for all you'd ever want to know about T-bar installations.

www.documents.dgs.ca.gov/dsa/.../IR_25-5_06-22-09.pdf

 

[Chamuit]

Let the paint dry first.

Uhm. Is that a problem where you are at? :grin:

 

[acrwc10]

Uhm. Is that a problem where you are at? :grin:

If you met some of the people I have had to work around, you wouldn't ask that.:grin: