300.4 (e)

[gunpowder]

The section states protection is to be provided against damage from roof replacement. If the roof is concrete above the steel decking, does the article apply? Is there a firm argument either way, or is it up the ahj?
Thanks

 

[infinity]

That section pertains to metal-corrugated roof decking which uses penetrating screws or other hold down devices not a concrete slab.

300.4(E) Cables, Raceways, or Boxes Installed in or Under
Roof Decking. A cable, raceway, or box, installed in ex-
posed or concealed locations under metal-corrugated sheet
roof decking, shall be installed and supported so there is not
less than 38 mm (1 1 ⁄ 2 in.) measured from the lowest surface of
the roof decking to the top of the cable, raceway, or box. A
cable, raceway, or box shall not be installed in concealed lo-
cations in metal-corrugated, sheet decking–type roof.
Informational Note: Roof decking material is often repaired
or replaced after the initial raceway or cabling and roofing
installation and may be penetrated by the screws or other me-
chanical devices designed to provide “hold down” strength of
the waterproof membrane or roof insulating material.

 

[jumper]

That section pertains to metal-corrugated roof decking which uses penetrating screws or other hold down devices not a concrete slab.

I have never understood why the roof guys need 6"-8" screws to get through a 3" roof.

 

[Carultch]

I have never understood why the roof guys need 6"-8" screws to get through a 3" roof.

Corrugation difference between the peak and valley, and the varying insulation thickness to give the roof its 1 degree drainage. Not worth the effort to use diverse screws and survey each position for if it is a peak or valley, and how thick the insulation is tapered.

 

[jumper]

Corrugation difference between the peak and valley, and the varying insulation thickness to give the roof its 1 degree drainage. Not worth the effort to use diverse screws and survey each position for if it is a peak or valley, and how thick the insulation is tapered.

IOW they are lazy.

 

[K8MHZ]

I have never understood why the roof guys need 6"-8" screws to get through a 3" roof.

I was told that there was actually a minimum amount the screws have to extend through the entire roof. I never saw that in writing, I was told that by one of the guys doing it on a job I was working.

 

[jumper]

I was told that there was actually a minimum amount the screws have to extend through the entire roof. I never saw that in writing, I was told that by one of the guys doing it on a job I was working.

Asking the Almighty, better known as a Google search, comes up with a value of 3/8" to 2 1/2" depending on roof materials and fasteners.

I understand that roofers prolly use screws a bit long for CYA, it just seems to me that many times the extra length is really, really overkill. Prolly just me.

 

[drcampbell]

I was told that there was actually a minimum amount the screws have to extend through ...

A length equal to the diameter or thread pitch, whichever is larger, suffices.

 

[MAC702]

I have never understood why the roof guys need 6"-8" screws to get through a 3" roof.

They don't have to bend over as far to get the screw started. :bye: