Take highest rating for C.I. from Table 11.2.1.1.A. for existing building

[sunyaer]

Ontario Building Code 2012, Division B – Part 11

Table 11.2.1.1.A.
Construction Index
Forming Part of Sentence 11.2.1.1.(1)
....

Notes to Table 11.2.1.1.A.:
(1) C.I. of 1 is lowest fire protection performance level and C.I. of 8 is highest.
(2) Take highest rating for C.I. from Table 11.2.1.1.A. for existing building.


I can't figure out what note (2) is saying. In my understanding, an existing building can only have one construction index (C.I.), how would the highest rating occur? ("take the highest rating" implies there are more than one rating for an existing building.

Could anyone shed some light on my confusion?

 

[tmurray]

Ontario Building Code 2012, Division B – Part 11

Table 11.2.1.1.A.
Construction Index
Forming Part of Sentence 11.2.1.1.(1)
....

Notes to Table 11.2.1.1.A.:
(1) C.I. of 1 is lowest fire protection performance level and C.I. of 8 is highest.
(2) Take highest rating for C.I. from Table 11.2.1.1.A. for existing building.


I can't figure out what note (2) is saying. In my understanding, an existing building can only have one construction index (C.I.), how would the highest rating occur? ("take the highest rating" implies there are more than one rating for an existing building.

Could anyone shed some light on my confusion?

I believe this note is clarifying that there is only one rating.

The only way this would make sense is that there are different areas of the building which each could fall within different construction indexes. Without this note, the designer could basically treat each area as a different construction index. This note clarifies what you believe, you select the most restrictive case and apply it to the whole building.

 

[sunyaer]

I believe this note is clarifying that there is only one rating.

The only way this would make sense is that there are different areas of the building which each could fall within different construction indexes. Without this note, the designer could basically treat each area as a different construction index. This note clarifies what you believe, you select the most restrictive case and apply it to the whole building.

If you select the most restrictive case, you would end up with the lowest rating for construction index, not the highest, am I correct? Or am I thinking the opposite way?

 

[tmurray]

I think it is the opposite. The lower the CI, the less restrictive (an 8 CI had floors rated at 3h where a 1 CI has them rated for 0h)

 

[sunyaer]

I think it is the opposite. The lower the CI, the less restrictive (an 8 CI had floors rated at 3h where a 1 CI has them rated for 0h)

OK. Let's assume an scenario of an existing building where there are three areas which could separately have construction index as 6, 5, and 3. For the evaluation of the whole building, I think the C.I. should be 3, the lowest, not 6, the highest, since C.I. is a representation of performance level that the building would provide against hazard (index) of existing or proposed occupancy.

If 6 is selected for C.I. in the above scenario, the building would be safe when a proposed occupancy with a corresponding hazard index not greater than 6. However, that's not the case, the areas which have C.I. value of 3 and 5 would be unsafe for a proposed occupancy with a corresponding hazard index of 6.

It makes sense to me only if the "highest rating" refers to the "fire-resistance rating" in the table which are used to determine C.I. , not the value of C.I.

Your comments?

 

[tmurray]

Looking at this again you classify the building as a C.I., so if you have multiple different fire resistance ratings throughout the building, you would go with the lowest level achieved by the whole building. You would not have separate C.I.s for a single building.

So, yes. In your example they would only get a classification of 3.

 

[sunyaer]

Looking at this again you classify the building as a C.I., so if you have multiple different fire resistance ratings throughout the building, you would go with the lowest level achieved by the whole building. You would not have separate C.I.s for a single building.

So, yes. In your example they would only get a classification of 3.

So, why is the building code using the word "highest", not "lowest?

 

[tmurray]

Because 3 is the highest rating achieved by the building in your example. Technically, 1 and 2 are also achieved.