Number of floors residential wiring vs commercial

[Robert Whiteaker]

In San Francisco there is a rule that if there are more than three floors of a multi-unit dwelling that all work must be to commercial code. I have not heard of any exception to that rule until today. A fellow said to me that if the third floor apartment had another level attached whether above or in this case below creating a fourth floor living area that the NEC code rule requiring the building be wired commercially did not apply.

This doesn't make any sense to me because a fire is a fire. I would imagine that the rule is there so that folks do not wire a hi rise in romex. Essentially with what the other contractor said is that you could stack two more floors on top of units that have two levels creating four floors and still wire in romex.

Could someone please help me with this? Thanks

 

[Robert Whiteaker]

Extra

Extra

In San Francisco there is a rule that if there are more than three floors of a multi-unit dwelling that all work must be to commercial code. I have not heard of any exception to that rule until today. A fellow said to me that if the third floor apartment had another level attached whether above or in this case below creating a fourth floor living area that the NEC code rule requiring the building be wired commercially did not apply.

This doesn't make any sense to me because a fire is a fire. I would imagine that the rule is there so that folks do not wire a hi rise in romex. Essentially with what the other contractor said is that you could stack two more floors on top of units that have two levels creating four floors and still wire in romex.

Could someone please help me with this? Thanks

I do want to mention that there are a very few buildings in San Francisco built around 1970 that have four floors and are wired residential that have a commercial floor below them and they are allowed to be wired in romex due to some weird grandfather clause having to do with the fact that they were allowed to be wired with romex in the first place.

So I guess there are always exceptions?

 

[LEO2854]

I do want to mention that there are a very few buildings in San Francisco built around 1970 that have four floors and are wired residential that have a commercial floor below them and they are allowed to be wired in romex due to some weird grandfather clause having to do with the fact that they were allowed to be wired with romex in the first place.

So I guess there are always exceptions?

I really think it's the building type verses how many floors.

look at 334.10,2011 NEC

 

[Robert Whiteaker]

Thank you

Thank you

Thank you. I found my answer in the second shaded paragraph where it basically says it is up to the local building code.

 

[iwire]

The 1999 NEC and previous cycles did not allow the use of NM above three stories

Starting with the 2002 NEC that prohibition was removed.

 

[Robert Whiteaker]

Thanks LEO2854

Thanks LEO2854

I suddenly realized that others will want to understand what I read and where in the article it was that I read it. I hope you folks have patience and will teach me how to refer to the Code. I have always enjoyed and believe in the spirit of teaching and learning and most importantly sharing experiences.

334.10 (thanks LEO2854)

The article says that a building that can structurally be built with wood can use NMC. For my purposes these buildings are multifamily buildings of four floors. These buildings house people and can catch fire easily so as with almost anything the local authority can always ask us to make things safer.

Specifically it says in the article that the selection of building construction types is regulated by the local building code, based on the occupancy, height, and area of the building.

It's important to learn very early about fire blocking, fire spaces, fire walls and sealing between individual units and what exactly is a firewall. That is a topic for another day. I have seen what can happen when a cabinet installer puts a 16 penny nail through a large bundle of NMC in an apartment kitchen wall near the sub panel. The breaker for the 20 amp circuit that was nailed did not throw and the resistance in the steel nail wasn't enough to throw the 100 amp main. Needless to say it melted the bundle together and that then threw the main. The melt down luckily was seen and happened quickly enough that there was minimal damage.

Our city of San Francisco allows a residential building of no more than three living floors to be wired in NMC (they do not consider a lobby floor or basement floor area or parking area to be living areas). In my case I have a lobby/laundry/trash/unfinished floor with three floors and 12 units above. The general contractor has been approved to make a living area connected by a staircase from the first floor to an area that was unfinished below it on the lobby floor.

The question:

Do the rooms connected by the staircase below the unit need to be wired with mc or conduit (commercially) now that the new construction makes the building have four living floors?

The answer:

It is up to the local building inspector and the local codes that they follow.

Hope this helps.