- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
I will post a picture later, but why is 300.4(E) exclusive to corrugated metal roof decking? Are cable and raceways installed under other types of roof decking not subject to damage?
300.4(E) Roof Decking
- Thread starter George Stolz
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I believe that it has to do with the long screws (about 4" I think) that are used in fastening the roof to this type of construction. For the record I hate this code change. :roll:
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I think that it's germane to how the roofing is installed over this type of decking. Long screws that penetrate the metal decking are the norm therefore anything underneath the decking is subject to penetration damage from a screw.
Now my broken record moment, I dislike this code rule. :roll:
Now my broken record moment, I dislike this code rule. :roll:
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I assume other types of roofs like roll tar roofs don't have the issue with the long screws. Not sure what they use.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
That would be my guess.
- Location
- Massachusetts
3-31 Log #3310 NEC-P03 Final Action: Reject
(300.4(E))
____________________________________________________________
Submitter: William Benard, State of New Hampshire,
Recommendation: Revise text to read as follows:
(E) Cables and Raceways installed under metal roof decking. Exposed and
concealed locations, where a cable- or raceway-type wiring method is installed
under metal roof decking, such as metal corrugated sheeting, the cable or
raceway shall be installed and supported so that the nearest outside surface of
the cable or raceway is not less than 32 mm (1 1/4 in.) from the nearest surface
of the sheet metal decking where screws are likely to penetrate when roofing
repairs or replacement occurs after the initial raceway installation. Where this
distance is not maintained, the cable or raceway shall be protected from
penetration by screws by a steel plate, sleeve, or equivalent at least 6.4 mm
(1/4 in.) thick.
(E) (F) Cables and Raceways Installed in Shallow Grooves
(Remaining text unchanged)
(F) (G) Insulated Fittings
(Remaining text unchanged)
Substantiation: The proposed subsection is intended to address the ?real
world? problem of physical damage to cables and raceway methods installed
below roof decks with insulating and waterproofing material secured above
using screws intended to penetrate the decking by at least 1 in. to meet
minimum manufacturer windsheer specifications. This method of fastening the
roofing material is fairly new to the industry replacing the old ?ballast hold
down? method typically utilized until the later ?80s. The new method of
screwing the roofing material down is causing substantial damage to all wiring
methods secured to the underside or located within 1.25 in. of the lowest point
of the decking material. Generally, roofing materials are replaced within 15
years of the original installation according to roofing manufacturers. The
probability of damage to the existing wiring methods increases substantially
during the re-roof process as longer screws are utilized to secure the new
roofing material.
The.25 in. protection allowance where the space is not maintained was
selected because it will provide sufficient protection to a cable or raceway
method installed in the suspect area. It is standard practice of a roofing
installation to not push the screw through the steel flange of the junior beam
supporting the decking from the underside of the deck. The flange of the junior
beam is typically at least.25 in. thick and, therefore, this would allow a cable or
raceway method to be run parallel to the underside of the supporting flange of
the junior beam.
Documentation exists to substantiate costly repairs required to replace
damaged raceways and cables in buildings where the wiring methods were
installed within the identified area subject to physical damage. The incidents of
damage are not limited to economic impact only, but can be linked to injury to
unqualified individuals attempting to reenergize the circuits while unaware of
the cause of the original failure.
Note: Supporting material is available for review at NFPA Headquarters.
Panel Meeting Action: Reject
Panel Statement: The installation covered in the proposal already seems to be
covered by the existing subsections in 300.4, so additional text in this section
would not seem to accomplish anything constructive. Roofers are faced with
exposed and concealed electrical raceways installed in existing buildings, and
they must be able to install the new roof without damage to the electrical
system. This proposal deals with repair or replacement of a metal roof, but
raceway and cable protection during a remodel would require a similar change
or a change would then be required where trusses or joists are removed during
structural damage repair. The individual building trades must take
responsibility for all work during repair or replacement of a roof or whatever
part of structure or building is under repair.
Number Eligible to Vote: 13
Ballot Results: Affirmative: 12 Negative: 1
Explanation of Negative:
CASPARRO, P.: I disagree with the panel statement that this particular
installation is covered in the existing subsections of 300.4. I do agree with the
submitter?s statement that a 1/4 in. spacing from the nearest surface of the sheet
metal roofing may not be enough. The presentation made during the panel
meeting showed decking screws as long as 6 in. with 3 in. to 4 in. protruding
below the sheet metal roof surface. The 1/4 in. protection plate could also be
penetrated by these screws since they are designed to penetrate the roof
decking. The answer is to not allow the conduits of any system; power,
communications, or life safety; to be that close to the roof decking.
____________________________________________________________
(300.4(E))
____________________________________________________________
Submitter: William Benard, State of New Hampshire,
Recommendation: Revise text to read as follows:
(E) Cables and Raceways installed under metal roof decking. Exposed and
concealed locations, where a cable- or raceway-type wiring method is installed
under metal roof decking, such as metal corrugated sheeting, the cable or
raceway shall be installed and supported so that the nearest outside surface of
the cable or raceway is not less than 32 mm (1 1/4 in.) from the nearest surface
of the sheet metal decking where screws are likely to penetrate when roofing
repairs or replacement occurs after the initial raceway installation. Where this
distance is not maintained, the cable or raceway shall be protected from
penetration by screws by a steel plate, sleeve, or equivalent at least 6.4 mm
(1/4 in.) thick.
(E) (F) Cables and Raceways Installed in Shallow Grooves
(Remaining text unchanged)
(F) (G) Insulated Fittings
(Remaining text unchanged)
Substantiation: The proposed subsection is intended to address the ?real
world? problem of physical damage to cables and raceway methods installed
below roof decks with insulating and waterproofing material secured above
using screws intended to penetrate the decking by at least 1 in. to meet
minimum manufacturer windsheer specifications. This method of fastening the
roofing material is fairly new to the industry replacing the old ?ballast hold
down? method typically utilized until the later ?80s. The new method of
screwing the roofing material down is causing substantial damage to all wiring
methods secured to the underside or located within 1.25 in. of the lowest point
of the decking material. Generally, roofing materials are replaced within 15
years of the original installation according to roofing manufacturers. The
probability of damage to the existing wiring methods increases substantially
during the re-roof process as longer screws are utilized to secure the new
roofing material.
The.25 in. protection allowance where the space is not maintained was
selected because it will provide sufficient protection to a cable or raceway
method installed in the suspect area. It is standard practice of a roofing
installation to not push the screw through the steel flange of the junior beam
supporting the decking from the underside of the deck. The flange of the junior
beam is typically at least.25 in. thick and, therefore, this would allow a cable or
raceway method to be run parallel to the underside of the supporting flange of
the junior beam.
Documentation exists to substantiate costly repairs required to replace
damaged raceways and cables in buildings where the wiring methods were
installed within the identified area subject to physical damage. The incidents of
damage are not limited to economic impact only, but can be linked to injury to
unqualified individuals attempting to reenergize the circuits while unaware of
the cause of the original failure.
Note: Supporting material is available for review at NFPA Headquarters.
Panel Meeting Action: Reject
Panel Statement: The installation covered in the proposal already seems to be
covered by the existing subsections in 300.4, so additional text in this section
would not seem to accomplish anything constructive. Roofers are faced with
exposed and concealed electrical raceways installed in existing buildings, and
they must be able to install the new roof without damage to the electrical
system. This proposal deals with repair or replacement of a metal roof, but
raceway and cable protection during a remodel would require a similar change
or a change would then be required where trusses or joists are removed during
structural damage repair. The individual building trades must take
responsibility for all work during repair or replacement of a roof or whatever
part of structure or building is under repair.
Number Eligible to Vote: 13
Ballot Results: Affirmative: 12 Negative: 1
Explanation of Negative:
CASPARRO, P.: I disagree with the panel statement that this particular
installation is covered in the existing subsections of 300.4. I do agree with the
submitter?s statement that a 1/4 in. spacing from the nearest surface of the sheet
metal roofing may not be enough. The presentation made during the panel
meeting showed decking screws as long as 6 in. with 3 in. to 4 in. protruding
below the sheet metal roof surface. The 1/4 in. protection plate could also be
penetrated by these screws since they are designed to penetrate the roof
decking. The answer is to not allow the conduits of any system; power,
communications, or life safety; to be that close to the roof decking.
____________________________________________________________
- Location
- Massachusetts
Looks like they changed their minds
3-10 Log #2040 NEC-P03 Final Action: Accept in Principle
(300.4(E))
____________________________________________________________
Submitter: William Benard, State of New Hampshire, Bureau of Electrical
Safety and Licensing
Comment on Proposal No: 3-31
Recommendation: Revise as follows:
(E) Cables and Raceways installed under roof decking. Exposed and
concealed locations, where a cable- or raceway-type wiring method is installed
under roof decking, such as metal corrugated sheeting, or other material that
supports a roof insulating and waterproofing membrane and will be penetrated
by screws or other mechanical devices designed to provide “hold down”
strength of the waterproofing membrane, the cable or raceway shall be installed
and supported so that the nearest outside surface of the cable or raceway is not
less than 38.1 mm (1 1/2 in.) from the nearest surface of the roof decking
where screws are likely to penetrate when roofing maintenance repairs or
replacement occurs before or after the initial raceway installation.
(E) (F) Cables and Raceways Installed in Shallow Grooves
(Remaining text unchanged)
(F)(G) Insulated Fittings
(Remaining text unchanged)
Substantiation: This proposal needs to be accepted as amended. The panel
members may not have completely understood the problem addressed in the
original proposal. The intention of the proposal is to prevent accidental
penetration of electrical cables and raceways under common flat roof decks.
The submitter did not intend to describe a scenario where the roof deck was
being replaced. Sufficient substantiation was provided to establish that this
problem does, indeed, exist.
Typically, the decking would remain unchanged and in its original condition.
The waterproofing and insulating material above conventional metal corrugated
sheeting is the element of repair or replacement. Roofing material
manufacturer’s installation standards mandate a self tapping deck screw to
penetrate the underside of the corrugated steel decking by at least 1 inch and up
to 1 1/4 inches. Minimum penetration provides “hold down” strength for the
insulating material above but becomes a hazard to anything within the lower
penetration proximity. Therefore, raceways located in close proximity to the
underside of the decking would be exposed to severe physical damage. This is
happening every single day during re-roofing projects that are only repairing or
replacing the waterproofing material on the surface of the roof of an occupied
building. It is not the first installation that is a concern because typically the
exterior insulation and waterproofing material of the flat roof is already in
place before the electrician begins to install the new wiring methods.
The selection of a minimum “38.1 mm (1 1/2 in.) from the nearest surface of
the roof decking where screws are likely to penetrate” was chosen after
measuring a multitude of installations where 38.1 mm (1 1/2 in.) was
discovered to be a minimum safe distance in a majority of installations from
the protruding screw at the lowest point of the underside of the roof deck.
The original panel statement alludes to a responsibility of the “individual
building trades” and an ability to stay away from electrical raceways that might
be located in harms way when making repairs to a damaged building. This
reroofing should not be considered as a repair but as routine maintenance. All
roofing material has a life that necessitates maintenance, repair, or replacement.
Is it the Panel’s intention to indicate that whenever a roofing material is
replaced the electrical wiring for the building has to be replaced as well? It
would be impracticable to provide a replacement of material above a finished
metal roof deck and be able to know where a roof could or could not penetrate
the decking with any one of a thousand deck screws. If any electrical wiring
methods are installed within a 1 1/2 inch proximity of the underside of the
metal decking, it is a sure bet that at least one electrical raceway or cable will
be damaged causing a failure to the electrical system. At the very least, an
overcurrent device will be called upon to hopefully prevent fire, personal injury
or possible electrocution. Considering the various voltages and inrush fault
currents available an imminent hazard will be present if an unqualified person
attempts to reset the device without clearing the fault at its origin. Refer to the
evidence submitted describing actual incidents. These incidents happen all too
often when the faults are created over retail outlets without the retail personnel
even being aware of work going on above them. There is no need to elaborate
the possible hazardous scenarios that could evolve from this potential.
I submit that this problem is at least as serious as the threat recognized and
addressed in the current section 300.4(D). If we are concerned about a
sheetrock screw penetrating a cable adjacent to a wall stud, then we should
recognize the similar hazard of a deck screw penetrating a metal raceway. The
proof is in the pudding see the photos I have provided.
The cut away roofing detail exemplifies the purpose for the screw installation
for roofing surface material installation, maintenance or replacement before
and after electrical wiring installations. Notice the screw penetration below the
underside of the metal decking. Photos exemplifying screw penetration are also
provided.
Retail store maintenance representatives and service electricians confirm that
re-roofing projects (replacing insulating and/or waterproofing material) causes
thousands of dollars of expenditure for repairs to electrical systems damaged
during membrane maintenance or repair. Copies of testimony with invoicing
for repair of damage caused by screws penetrating electrical conduit is
provided as evidence.
Photos (1, 2, and 3) accompaning with this proposal provide evidence of
damage to wiring methods in the identified area. The incident cascaded to
personal injury when unqualified individuals in the retail store repeatedly
attempted to reset an overcurrent device supplying a 277 volt lighting circuit
without consideration to the increased hazards from the repeated short circuit.
Note: Supporting material is available for review at NFPA Headquarters.
Panel Meeting Action: Accept in Principle
Revise recommended text to read:
“(E) Cables and Raceways Installed Under Roof Decking. A cable- or
raceway-type wiring method, installed in exposed or concealed locations under
metal-corrugated sheet roof decking, shall be installed and supported so the
nearest outside surface of the cable or raceway is not less than 38 mm (1 1/2
in.) from the nearest surface of the roof decking.
FPN: 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 mechanical devices designed to provide “hold down” strength
of the water-proof membrane or roof insulating material.
Exception: Rigid metal conduit and intermediate metal conduit shall not be
required to comply with 300.4(E).”
Reidentify existing 2005 NEC subdivisions (E) and (F) as (F) and (G)
Panel Statement: The proposed text was revised for clarity and ease of use.
Some of the wording within the proposal was informative text that fit better as
a fine print note and the exception was added to cover rigid and IMC that
would not suffer damage from these hold-down devices or screws. The metric
measurement was changed to a hard conversion, as it is the panel’s opinion that
the 0.1 mm provided in the soft conversion was not critical.
Number Eligible to Vote: 13
Ballot Results: Affirmative: 13
Comment on Affirmative:
CASPARRO, P.: Allowing additional room between the underside of roof
decking and where a cable or raceway type wiring methods is allowed to be
installed should alleviate damage to these cables and raceways.
SLEIGHTS, J.: I support the panel action on this proposal in recognition of
the problem with the following comment.
There was no substantiation for the addition of the exception for RMC and
IMC and it should not have been included.
3-10 Log #2040 NEC-P03 Final Action: Accept in Principle
(300.4(E))
____________________________________________________________
Submitter: William Benard, State of New Hampshire, Bureau of Electrical
Safety and Licensing
Comment on Proposal No: 3-31
Recommendation: Revise as follows:
(E) Cables and Raceways installed under roof decking. Exposed and
concealed locations, where a cable- or raceway-type wiring method is installed
under roof decking, such as metal corrugated sheeting, or other material that
supports a roof insulating and waterproofing membrane and will be penetrated
by screws or other mechanical devices designed to provide “hold down”
strength of the waterproofing membrane, the cable or raceway shall be installed
and supported so that the nearest outside surface of the cable or raceway is not
less than 38.1 mm (1 1/2 in.) from the nearest surface of the roof decking
where screws are likely to penetrate when roofing maintenance repairs or
replacement occurs before or after the initial raceway installation.
(E) (F) Cables and Raceways Installed in Shallow Grooves
(Remaining text unchanged)
(F)(G) Insulated Fittings
(Remaining text unchanged)
Substantiation: This proposal needs to be accepted as amended. The panel
members may not have completely understood the problem addressed in the
original proposal. The intention of the proposal is to prevent accidental
penetration of electrical cables and raceways under common flat roof decks.
The submitter did not intend to describe a scenario where the roof deck was
being replaced. Sufficient substantiation was provided to establish that this
problem does, indeed, exist.
Typically, the decking would remain unchanged and in its original condition.
The waterproofing and insulating material above conventional metal corrugated
sheeting is the element of repair or replacement. Roofing material
manufacturer’s installation standards mandate a self tapping deck screw to
penetrate the underside of the corrugated steel decking by at least 1 inch and up
to 1 1/4 inches. Minimum penetration provides “hold down” strength for the
insulating material above but becomes a hazard to anything within the lower
penetration proximity. Therefore, raceways located in close proximity to the
underside of the decking would be exposed to severe physical damage. This is
happening every single day during re-roofing projects that are only repairing or
replacing the waterproofing material on the surface of the roof of an occupied
building. It is not the first installation that is a concern because typically the
exterior insulation and waterproofing material of the flat roof is already in
place before the electrician begins to install the new wiring methods.
The selection of a minimum “38.1 mm (1 1/2 in.) from the nearest surface of
the roof decking where screws are likely to penetrate” was chosen after
measuring a multitude of installations where 38.1 mm (1 1/2 in.) was
discovered to be a minimum safe distance in a majority of installations from
the protruding screw at the lowest point of the underside of the roof deck.
The original panel statement alludes to a responsibility of the “individual
building trades” and an ability to stay away from electrical raceways that might
be located in harms way when making repairs to a damaged building. This
reroofing should not be considered as a repair but as routine maintenance. All
roofing material has a life that necessitates maintenance, repair, or replacement.
Is it the Panel’s intention to indicate that whenever a roofing material is
replaced the electrical wiring for the building has to be replaced as well? It
would be impracticable to provide a replacement of material above a finished
metal roof deck and be able to know where a roof could or could not penetrate
the decking with any one of a thousand deck screws. If any electrical wiring
methods are installed within a 1 1/2 inch proximity of the underside of the
metal decking, it is a sure bet that at least one electrical raceway or cable will
be damaged causing a failure to the electrical system. At the very least, an
overcurrent device will be called upon to hopefully prevent fire, personal injury
or possible electrocution. Considering the various voltages and inrush fault
currents available an imminent hazard will be present if an unqualified person
attempts to reset the device without clearing the fault at its origin. Refer to the
evidence submitted describing actual incidents. These incidents happen all too
often when the faults are created over retail outlets without the retail personnel
even being aware of work going on above them. There is no need to elaborate
the possible hazardous scenarios that could evolve from this potential.
I submit that this problem is at least as serious as the threat recognized and
addressed in the current section 300.4(D). If we are concerned about a
sheetrock screw penetrating a cable adjacent to a wall stud, then we should
recognize the similar hazard of a deck screw penetrating a metal raceway. The
proof is in the pudding see the photos I have provided.
The cut away roofing detail exemplifies the purpose for the screw installation
for roofing surface material installation, maintenance or replacement before
and after electrical wiring installations. Notice the screw penetration below the
underside of the metal decking. Photos exemplifying screw penetration are also
provided.
Retail store maintenance representatives and service electricians confirm that
re-roofing projects (replacing insulating and/or waterproofing material) causes
thousands of dollars of expenditure for repairs to electrical systems damaged
during membrane maintenance or repair. Copies of testimony with invoicing
for repair of damage caused by screws penetrating electrical conduit is
provided as evidence.
Photos (1, 2, and 3) accompaning with this proposal provide evidence of
damage to wiring methods in the identified area. The incident cascaded to
personal injury when unqualified individuals in the retail store repeatedly
attempted to reset an overcurrent device supplying a 277 volt lighting circuit
without consideration to the increased hazards from the repeated short circuit.
Note: Supporting material is available for review at NFPA Headquarters.
Panel Meeting Action: Accept in Principle
Revise recommended text to read:
“(E) Cables and Raceways Installed Under Roof Decking. A cable- or
raceway-type wiring method, installed in exposed or concealed locations under
metal-corrugated sheet roof decking, shall be installed and supported so the
nearest outside surface of the cable or raceway is not less than 38 mm (1 1/2
in.) from the nearest surface of the roof decking.
FPN: 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 mechanical devices designed to provide “hold down” strength
of the water-proof membrane or roof insulating material.
Exception: Rigid metal conduit and intermediate metal conduit shall not be
required to comply with 300.4(E).”
Reidentify existing 2005 NEC subdivisions (E) and (F) as (F) and (G)
Panel Statement: The proposed text was revised for clarity and ease of use.
Some of the wording within the proposal was informative text that fit better as
a fine print note and the exception was added to cover rigid and IMC that
would not suffer damage from these hold-down devices or screws. The metric
measurement was changed to a hard conversion, as it is the panel’s opinion that
the 0.1 mm provided in the soft conversion was not critical.
Number Eligible to Vote: 13
Ballot Results: Affirmative: 13
Comment on Affirmative:
CASPARRO, P.: Allowing additional room between the underside of roof
decking and where a cable or raceway type wiring methods is allowed to be
installed should alleviate damage to these cables and raceways.
SLEIGHTS, J.: I support the panel action on this proposal in recognition of
the problem with the following comment.
There was no substantiation for the addition of the exception for RMC and
IMC and it should not have been included.
Last edited:
bphgravity
Senior Member
- Location
- Florida
I agree with the other statements. For most other roof coverings, no additional fastners or exposed screws / nails will be present. In fact, the buildings codes require missed nails (shiners) in wood sheathed roof coverings to be pulled and re-nailed. Once dried-in, there are likely no other penetrations through the roof covering that would present a hazard to electrical wiring.
Metal roofing is a little different. Not all fasteners are embedded within the framing. Many are exposed at seam and lap connection points. In addtion, insulated roof systems are typcially installed after the placement of the metal roof decking and after electrical work has started. Typcial systems call for 4" inch insulation board screwed off with 8-12" fasteners 6"on the edges and 12" in the field. These screws penetrate through the decking into open ceiling spaces where cables and raceways may be present.
Metal roofing is a little different. Not all fasteners are embedded within the framing. Many are exposed at seam and lap connection points. In addtion, insulated roof systems are typcially installed after the placement of the metal roof decking and after electrical work has started. Typcial systems call for 4" inch insulation board screwed off with 8-12" fasteners 6"on the edges and 12" in the field. These screws penetrate through the decking into open ceiling spaces where cables and raceways may be present.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Let's spin this a bit. I install a light in a residential attic, and due to a prescription overdose decide it would be great fun to staple the NM to the roof sheathing from the peak to the exterior wall, and then drill a hole and disappear into the wall.
Which code have I violated?
Will this cable be immune from being nailed by the roofers? I seem to recall bumping my head and shoulders on nails in attics before, but perhaps I am misremembering.
I wish I had taken that picture. There was a NM routed over the top of a huge lam, in the half-inch gap between the beam and the roof decking. I was mortified when I saw it on inspection walk, and was very surprised to see nothing to speak of in the code that forbade it.
Which code have I violated?
Will this cable be immune from being nailed by the roofers? I seem to recall bumping my head and shoulders on nails in attics before, but perhaps I am misremembering.
I wish I had taken that picture. There was a NM routed over the top of a huge lam, in the half-inch gap between the beam and the roof decking. I was mortified when I saw it on inspection walk, and was very surprised to see nothing to speak of in the code that forbade it.
- Status