# Mounting UFO Highbays to Purlins



## joebanana (Dec 21, 2010)

Beam clamps and uni-strut.


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## Forge Boyz (Nov 7, 2014)

How about this?








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## Navyguy (Mar 15, 2010)

We just installed a few of them in a garage; drilled the beam for a 3/8" eye bolt, used a lock link / screw link at each end of a 3/4" chain. Chain was overkill, but wanted to match the lock link size and the "industrial look" of the garage.

Unfortunately I can't seem to find the pictures...

We are putting up some more in a wood truss shop next week. We will do a similar approach, but will likely just use 10-T jack chain, which is plenty strong to hold the fixture.

Cheers

John


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## sparky80 (Aug 1, 2016)

Is drilling the bottom of the purlin an issue?


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## Forge Boyz (Nov 7, 2014)

Not that I know of. I hung some on i-beams and was told by the GC that I could drill them for eyebolts that I used.

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## telsa (May 22, 2015)

You sound like you've got purlin and truss crossed up. 

A purlin is RIGHT UP TO THE ROOF LINE. It's what the roof, itself, is attached to. 

High bays are just about NEVER attached to purlins... especially in commercial schemes.

The usual drill is for high bays to be mounted to the truss system... and for purlins atop the truss array... with the roof attached to the purlins... with the roof rough-in performed with modular elements that just drop in place. The weather proofing is then attached atop the modules to create a seamless weather barrier.

If your build really has the high bays attached all the way to the purlins, post a photo.

I want to see that.

BTW, the lower cord of the truss is often used by the other trades for this and that. But it's not where any structural engineer wants to see any serious load. Pulling downward on the bottom of a truss assembly greatly weakens it. That's why you'll see plumbers and pipe fitters going to the extra effort of rigging their hefty loads to the tops of the trusses. ( especially the open frame metal trusses so common these days in commercial and warehouse builds.)


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## Navyguy (Mar 15, 2010)

I think purlin is correct

http://sgcalabama.com/wp-content/uploads/2016/06/StructureImage1.png

at least in my example.

Cheers
John


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## gpop (May 14, 2018)

If the conduit and boxes have not been installed then heavy duty boxes with swivel mount fixture hangers would be a option. They have a 1/2 threaded female that you can add a hook or a piece of conduit to adjust the height.


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## macmikeman (Jan 23, 2007)

When I hear Purlin, I think about that z-bar sandwich looking thing that has a slot all the way across the bottom between two angle bars with z shaped or x pattern rods that zig zag up to the upper side which is a repeat of the lower . They are like roof truss only much stronger. I slide threaded rod thru the slot, washers and 3/8 rod nuts on top side and maybe the same on the bottom for some fixtures, especially ceiling fans in public schools that use that type of truss. The UFO'S usually Come with a backplate that has some holes in it for your rod and washers and nuts to support it . Ain't coming loose off there, but usually also there is some safety chain in the box the light comes in. Wrap that round the bottom cord of the purlin truss and secure with a two piece horseshoe nut.


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## B-Nabs (Jun 4, 2014)

macmikeman said:


> When I hear Purlin, I think about that z-bar sandwich looking thing that has a slot all the way across the bottom between two angle bars with z shaped or x pattern rods that zig zag up to the upper side which is a repeat of the lower . They are like roof truss only much stronger.


I know those as Wilson joists. 


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## sparky80 (Aug 1, 2016)

joebanana said:


> Beam clamps and uni-strut.


Do you mean beam clamping unistrut between Purlins and then hang the fixture from the Unistrut?


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## sparky80 (Aug 1, 2016)

If I remember right they are CEE purlins if that helps anyone visualize. Thanks for the replies.


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## splatz (May 23, 2015)

There are all different kinds of purlins, I doubt there is an ANSI standard definition, usually any part of the roofing structure that runs parallel to the eaves on a pitched roof is called a purlin. 

Generally you either have a lot of rafters / bar joists parallel to the roof span, or a few purlins between beams, with the purlins perpendicular to the beam span. 

The one @Navyguy linked to, used on the prefab steel kit buildings, I usually see those Z shaped. Because there's so much span between the steel beams that support the roof, in a lot of spots that's the only thing nearby to hang stuff off. 

I have beam clamped directly to these many many times without any issue other than OCD saying any angle that's not a right angle is a wrong angle. As usual the people at Erico Caddy are looking out for you, they have purlin clips for every occasion 

https://www.erico.com/category.asp?category=R1317 

The kicker is when you need lights where there's no beam or purlin to hang them off. As long as the purlins are less than 10' apart, you can attach strut between purlins. If they're over 10' apart, it's a treat, you can special order 20' strut but what a pain in the ass and expensive. You can easier and cheaper get steel studs 16', double them up and make a box, and they will support a fair amount of weight, but said and done just as bad pain in the ass.


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## splatz (May 23, 2015)

sparky80 said:


> Is drilling the bottom of the purlin an issue?


I don't know an actual official rule of thumb but I doubt it with holes for tek screws or 1/4" or 3/8" bolts. They screw the roof into the purlins and they screw the wall sheathing to the girts so there's lots of small holes in them. 

If you had to drill a big hole in the standing / vertical part of the C or Z purlin I guess there must be some limit how big a hole you can drill. 

But, the caddy clips ... no reason to drill them.


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## joebanana (Dec 21, 2010)

sparky80 said:


> Do you mean beam clamping unistrut between Purlins and then hang the fixture from the Unistrut?


If need be, or just a beam clamp. Caddy makes a purlin bang-on clip for conduit, maybe they have something for lights?


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## splatz (May 23, 2015)

joebanana said:


> if need be, or just a beam clamp. Caddy makes a purlin bang-on clip for conduit, maybe they have something for lights?


maybe they do.


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## Southeast Power (Jan 18, 2009)

We just had a project where we had to use beam clamps with the threaded hole in the side and had to attach to the upper part of the joist.
If you are able to drill a small hole in a piece of sheet metal and attach a hook for a 5lb fixture, I dont think the building would collapse. :wink:


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