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NMD in 3 story residential building

3435 Views 22 Replies 5 Participants Last post by  jammin9
I have a building to wire that is 3 stories. The original building (combustible) takes up the first 2 floors and half way back where add ons were constructed (non-combustible) for the back portion and the upper 3rd floor. the first floor is commercial space, and the top 2 floors are residential units. The residential units have been fire seperated from the common areas and the commercial space. is in ok to use NMD for these residential spaces and if so where in the Ontario or Canadian building code does it say its ok. All I found in Part 9 stating that except dwelling units nmd has to be used in combustible construction.

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I have some limited and dated experience with this stuff so I will throw in what I can...

Ontario Building Code 2012 – Division A Dwelling unit means a suite operated as a housekeeping unit, used or intended to be used by one or more persons and usually containing cooking, eating, living, sleeping and sanitary facilities.

Division B 3.1.2 .1- Classification of Buildings (1) Except as provided by Articles to, every building or part of it shall be classified according to its major occupancy as belonging to one of the Groups or Divisions described in Table

So the question is the building classified as a Group C (no division) “Residential Occupancy” or some other rating because of the business type in the other sections of the building? What I have found is that only if the “sections” of the building are fully separated by fire separation will you get a multiple occupancy rating.

In section 3.1.3 Multiple Occupancy Requirements talks about the separation requirements... without putting the whole section out there... essentially you need the higher fire ratings because of the lack of separation between the units, thus FT1 wire (standard NMD) is not acceptable and must be wired in BX FT6 or conduit having a FT4 rating. This is also interconnected with the plenum requirements (like above drop ceiling, etc) where FT6 rated cables must be used.

So you need to find out what the classification of the building is... I am assuming it will not be Group C... and wire according to those requirements. This will also force you to consider all the fire alarm issues (pull stations, interconnected smoke alarms, heat detectors, etc).


John Kuehnl-Cadwell
Master Electrician
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Perfect. Then get the architect to show the multiple occupancy ratings / classifications to the building inspector and the ESA inspector and you should be good to go with NMD90.


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