outriggers on joist roof

[tw]

Doing a school with steel joist roof and cmu bearing walls. The building has a 4 ft roof overhang all around. I'm using joist extensions on the side perpendicular to joists. My question is on the sides parallel to joists. I've never used the loose outriggers from the joist mfg. cuz they say they aren't U.L. approved and I've always solved it some other way. This job has no simple solutions in that the spans are long and the allowable structure depth inside the eave/overhang is very limited, so the outriggers would be ideal.

2 questions:

Anybody used the outriggers and what was your experience? Is it still true that the outriggers are not U.L. approved?

tw

 

[ali07]

You can use outriggers with a moment connection with suppoerting beams on either side and continue it to the joist so that it will balance torsional moment of the overhang portion. You might need this close to the location of joist bridging.

 

[Grizzman]

when I use outriggers, I almost exclusively use hSS 1.1/2 or 2.1/2. I can't truly state the UL rating of HSS though.

 

[civeng80]

Who are the joist manufacturers and what type of outriggers are you referring to ? Have you got purlins which can be extended on the side?

 

[tw]

The Vulcraft 2.5K series. I have substantial (44LH10 and the like) joists/trusses running parallel w/ exterior CMU wall, similar condition to what is shown in Vulcraft catalog for what outriggers are for. But the U.L. thing is a show-killer I believe.

tw

 

[JAE]

We've used the Vulcraft extensions. No problems. Don't know why you say a U.L. rating is required per code.

 

[jike]

I agree. I have done many jobs with outriggers that have never required a UL rating.

Your biggest problem with a 4 foot overhang will be uplift on the 1st interior member. You may need a moment connection there and extend back to the 2nd interior member to reduce uplift.

I hope the snow load is not too great! Don't forget about wind uplift on the overhang!

 

[JAE]

Yes.

The biggest issue we had was that the architect wanted to slope the roof (1/4" per foot) and they wanted the outriggers wanted to be level... can't have both.

So we had to make the structure level and use tapered insulation to get the roof slope.

 

[jike]

JAE:

We have had the same request multiple times also. We have achieved this with varying steel heights to get the edge level but it is not an easy thing to accomplish.

 

[civilperson]

Why do you need UL approval?

 

[tw]

The roof is UL rated by the architect, I thought. Turns out it is not so this has just been a little ado about nothing. Thanks for the replies.

 

[JAE]

As Gilda Radner would say...."never mind" (cue the sheepish grin)