• Welcome to The Building Code Forum

    Your premier resource for building code knowledge.

    This forum remains free to the public thanks to the generous support of our Sawhorse Members and Corporate Sponsors. Their contributions help keep this community thriving and accessible.

    Want enhanced access to expert discussions and exclusive features? Learn more about the benefits here.

    Ready to upgrade? Log in and upgrade now.

What makes a ceiling "structural"? NEC 110.26(E)(1)

Y

Yikes

SAWHORSE
Joined
Nov 2, 2009
Messages
4,267
Location
Southern California
Apartment building has 2nd floor bathtub waste lines travelling horizontally over dedicated electrical spaces in an electrical room on the first floor. California / NEC 110.26 (E)(1) will require a "structural ceiling" to separate these pipes from the electrical space below. It further says "A dropped, suspended, or similar ceiling that does not add strength to the building structure shall not be considered a structural ceiling."

What do they mean by "add strength to a structure?" How does any separate ceiling "add strength"?
Furthermore, they have an exception to allow suspended ceilings with panels, but they also indicate that the suspended ceiling must add strength to the structure????

I'd like to propose gyp board on steel or wood ceiling joists, to create an interstitial space for the pipes that is below the 1-hour rated structural floor-ceiling assembly.

Here's the actual wording of the code:


100.26(E)(1) Indoor
Indoor installations shall comply with 110.26(E)(1)(a) through (E)(1)(d).

(a) Dedicated Electrical Space. The space equal to the width and depth of the equipment and extending from the floor to a height of 1.8 m (6 ft) above the equipment or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation. No piping, ducts, leak protection apparatus, or other equipment foreign to the electrical installation shall be located in this zone.​
​
Exception: Suspended ceilings with removable panels shall be permitted within the 1.8-m (6-ft) zone.​
​
(b) Foreign Systems. The area above the dedicated space required by 110.26(E)(1)(a) shall be permitted to contain foreign systems, provided protection is installed to avoid damage to the electrical equipment from condensation, leaks, or breaks in such foreign systems.​
​
(c) Sprinkler Protection. Sprinkler protection shall be permitted for the dedicated space where the piping complies with this section.​
​
(d) Suspended Ceilings. A dropped, suspended, or similar ceiling that does not add strength to the building structure shall not be considered a structural ceiling.​
 
Yikes said:
What do they mean by "add strength to a structure?" How does any separate ceiling "add strength"?
Click to expand...

The only thing I can think of is ceiling framing acting as lateral support for a pitched roof. Or possibly where a framed ceiling is designed to provide lateral bracing of tall structural walls. Those ceilings would be shown on the structural drawings.
 
mtlogcabin said:
Every suspended ceiling in your seismic zone needs to be designed to ASCE 7 which is a structural design
Click to expand...
Right, but how does a suspended ceiling “add strength to the building”?

Maybe I’m stuck on terminology, but unless the ceiling is designed to support something elsewhere in the building (either vertical or lateral loads), it seems like it would be either net neutral or would be adding more load but not more strength.

Are we saying that just taking care of its own loads and transferring those loads into other building elements is considered “adding strength”?
 
Yikes said:
Furthermore, they have an exception to allow suspended ceilings with panels, but they also indicate that the suspended ceiling must add strength to the structure????
Click to expand...
No, the language about suspended ceilings is meant to indicate that they are not considered "foreign equipment" that is prohibited from passing above the footprint of the panelboard enclosure. There is no requirement that they be structural for the exception to apply.

Cheers, Wayne
 
While you can meet the letter of the code, a drywall lid is not much of a guarantee that water will never get to the electrical equipment. If you are dealing with new construction, a ceiling cures the dilemma.

Your issue is the possibility of water leaking from the pipes and presenting a hazard with the electrical equipment. I had a similar situation with an existing restaurant. The only way to change it up was to move the kitchen or the electrical. As I recall, it was 800A switch gear. I allowed a diverter over the gear that would direct any water away from the equipment. That was not perfect but then there's not a lot in life that is.
 
wwhitney said:
No, the language about suspended ceilings is meant to indicate that they are not considered "foreign equipment" that is prohibited from passing above the footprint of the panelboard enclosure. There is no requirement that they be structural for the exception to apply.

Cheers, Wayne
Click to expand...
(a) Dedicated Electrical Space. The space equal to the width and depth of the equipment and extending from the floor to a height of 1.8 m (6 ft) above the equipment or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation. No piping, ducts, leak protection apparatus, or other equipment foreign to the electrical installation shall be located in this zone.
(d) Suspended Ceilings. A dropped, suspended, or similar ceiling that does not add strength to the building structure shall not be considered a structural ceiling.

I want to run pipes under my 1 hour apartment floor/ceiling assembly. Those pipes will be less than 6' above the equipment. Therefore, according to (a), I must install a "structural ceiling" below the pipes/ above the equipment.
So what kind of ceiling constitutes a "structural ceiling"?

Yes, this is brand-new construction. I was thinking of just putting in a gyp board ceiling mounted on 2x6 ceiling joists, about 12" below the fire-rated floor ceiling assembly.
 
Yikes said:
I want to run pipes under my 1 hour apartment floor/ceiling assembly. Those pipes will be less than 6' above the equipment. Therefore, according to (a), I must install a "structural ceiling" below the pipes/ above the equipment.
Click to expand...
That's correct, unless you can move the panel (including possibly downard to get to 6') or the pipes so that the pipes do not cross over the footprint of the panel. If these pipes are running perpendicular to the plane of the face of the panel(s), you can't shift them to the side to go around or pass between panels?

Yikes said:
So what kind of ceiling constitutes a "structural ceiling"?
Click to expand...
Good question, and the interpretation will vary between AHJs. But 110.26(E)(1)(d) provides some insight, in that it tells us a suspended ceiling is not a structural ceiling. Presumably because the structure carrying the weight of the ceiling tiles is the higher, "structural" ceiling. So if you frame in ceiling joists to carry a gypsum board ceiling, those joists would now be structural (they have to carry the weight of the gypsum board), and so that would be your structural ceiling.

Of course, this line of thought suggests that you could also add new ceiling joists and suspend a suspended ceiling from them, and that would work as well. No idea how well that idea would go over with a typical AHJ, but it seems logical to me.

Cheers, Wayne
 
Maybe not quite on track, but many years ago - mid 1980s - I designed a theatrical lighting system for a department store in a mall in Roanoke VA. They had put a shingles roof over my dimmer panel in a mechanical room because of piping over it. I thought fire sprinkler but 40 years obscures things.
 
You must log in or register to reply here.
Back
Top