fastener for metal roofing

Status
Not open for further replies.
M

MannyBurgos

Senior Member
Location
Waukegan, IL
What type of fastners is used to secure heavywall conduit straps to the underside of metal roof decking? I will be working on a commercial project which requires mounting heavywall to the underside of the roof. Don't have too much experience with this type of install so your help will be much appreciated.
 
We normally used a self-drilling Tex screw. For RMC you would probably want a #12 or #14 screw in the appropriate length.

TekScrews.jpg
 
MannyBurgos said:
thank you Infinity. what is the typical length that is used?
Click to expand...

Really depends on the thickness of your strap and if you're using a back strap spacer behind the RMC. Rigid straps are pretty thick so I would guess that 1.25-1.5" long should do. You need a screw that's long enough to get past the self-drilling tip and into the threads.
 
infinity said:
Really depends on the thickness of your strap and if you're using a back strap spacer behind the RMC. Rigid straps are pretty thick so I would guess that 1.25-1.5" long should do. You need a screw that's long enough to get past the self-drilling tip and into the threads.
Click to expand...

Thanks Infinity. I appreciate your response.
 
MannyBurgos said:
What type of fastners is used to secure heavywall conduit straps to the underside of metal roof decking? I will be working on a commercial project which requires mounting heavywall to the underside of the roof. Don't have too much experience with this type of install so your help will be much appreciated.
Click to expand...

I hope that was mis-stated. You'd never fasten directly to the underside of the roof deck. You'd fasten to the purlins supporting the roof deck.
 
Maybe we're talking about different things.

With a corrugated roof deck which has a few inches or more of iso on top and a hop mopped roof covering above that, I can see a screw penetrating the lower surface of the corrugated deck. Imagine a deck with 1.5"corrugation. The screw never gets to the water barrier.

But with a deck such as a 5-V style where the steel sheet is the roof covering, you would not want to penetrate that with a screw protruding through the water barrier.
 
MannyBurgos said:
This type of roof. Straps to be attached to the lower side of the canals.
Click to expand...

I think the problem is that when the roof gets replaced they will likely screw insulation boards down through the corrugated deck. If you conduit it right where one of the thousands of screws lands it will screw right into your conduit. Kaboom
 
mkgrady said:
I think the problem is that when the roof gets replaced they will likely screw insulation boards down through the corrugated deck. If you conduit it right where one of the thousands of screws lands it will screw right into your conduit. Kaboom
Click to expand...

Just my 2 cents but those roofing screws will probably not go through RMC.
 
mkgrady said:
I think the problem is that when the roof gets replaced they will likely screw insulation boards down through the corrugated deck. If you conduit it right where one of the thousands of screws lands it will screw right into your conduit. Kaboom
Click to expand...

Sucks to be the roofer at that point. Nec nor does local ahj restrict from such installation. Hence the reason for rmc (2011 code cycle). This is how client wants job so this is how i will do it. All of his existing pipes are attached to underside and they are emt. I just hope he carries an extra pair of clean underwear with em.
 
ActionDave said:
I fondly remember the days when I could stand in a lift and shove a stick after stick of EMT between the roof and the bar joists. With a little jiggle you get out sixty feet before moving the lift.
Click to expand...

There are tens of thousands of warehouses and buildings wired that way in EMT with seemingly little problems. :roll:
 
Status
Not open for further replies.
Top