Fire Separation between Group F2 and C

[XE1805]

Have a question about continuity of a 2 hr fire separation where a group C Residential occupancy sits on top of a Group F2 Industrial Occupancy. Basically putting an apartment above an F2 fabrication shop. See attached section sketch of the situation.

Existing F2 shop, wood framed, 2 storey, no sprinkler, all combustible framing. Project is to add an extension to the shop off the back wall of the ground floor, and then put a single apartment above. NBCC Occupancy matrix says a 2hr fire separation required between those 2 occupancies. Final building will likely be just over 600sm in building area.

It's clear the that the floor between the apartment and the shop extension needs to be rated. What is less clear is if the vertical exterior wall of the apartment that sits above the shop also needs the same rating if the existing adjacent roof is combustible and not rated.

I am looking for some specific NBCC code references that apply in this situation. 3.1.7.3(3) says 'Exterior walls shall be rated from exposure to fire from inside the building.' which would not be the case here. Have not yet investigated the need for sprinklers.

thanks

 

[Feanor]

Looks like you have an R2 occupancy.
The 2-hr barrier satisfies Chapter 5 table 508.4.
To address the exterior wall fire rating you have to see table 601.
To address the allowable openings, see table 705.5. What is the distance between the blue and the red walls? What type of construction would the new apartment be?

 

[RLGA]

Looks like you have an R2 occupancy.
The 2-hr barrier satisfies Chapter 5 table 508.4.
To address the exterior wall fire rating you have to see table 601.
To address the allowable openings, see table 705.5. What is the distance between the blue and the red walls? What type of construction would the new apartment be?

This is a Canadian code question.

XE2805, most of the people on this forum are U.S.-based and are more familiar with the IBC, so a response to your question may be slow in coming.

 

[XE1805]

Looks like you have an R2 occupancy.
The 2-hr barrier satisfies Chapter 5 table 508.4.
To address the exterior wall fire rating you have to see table 601.
To address the allowable openings, see table 705.5. What is the distance between the blue and the red walls? What type of construction would the new apartment be?

Thanks, IBC code references are helpful, I can cross reference with Canadian National Building Code. Apartment ideally would be combustible wood construction but non-combustible is an option.

 

[XE1805]

This is a Canadian code question.

XE2805, most of the people on this forum are U.S.-based and are more familiar with the IBC, so a response to your question may be slow in coming.

Thanks, understood, IBC code references are still helpful.

 

[tmurray]

See:
3.2.3.15. wall exposing adjoining roof
3.2.3. spatial separation (applies to adjacent buildings AND two different fire compartments in the same building)

 

[XE1805]

See:
3.2.3.15. wall exposing adjoining roof
3.2.3. spatial separation (applies to adjacent buildings AND two different fire compartments in the same building)

thanks, given the areas and construction type, I believe the building would be under 3.2.2.76 for major occupancy with 3.2.2.53 minor so this is all making sense -

 

[XE1805]

Hi, I have another (maybe dumb) question I've never really quite understood. In the condition where a floor assembly is required to be a 'fire separation' with a fire resistance rating', and the supporting structure of load bearing walls, columns, and arches are required to have an equivalent 'fire resistant rating', does that mean that un-rated openings are not permitted in the load bearing wall? ie: can you have an un-rated window in an exterior load bearing wall that is required to have a fire resistance rating? Seems like the window or door is a weak point. If the intent is to just protect the structure, do you have to wrap 5/8" gyprock into the window opening?

 

[Feanor]

Hi, I have another (maybe dumb) question I've never really quite understood. In the condition where a floor assembly is required to be a 'fire separation' with a fire resistance rating', and the supporting structure of load bearing walls, columns, and arches are required to have an equivalent 'fire resistant rating', does that mean that un-rated openings are not permitted in the load bearing wall? ie: can you have an un-rated window in an exterior load bearing wall that is required to have a fire resistance rating? Seems like the window or door is a weak point. If the intent is to just protect the structure, do you have to wrap 5/8" gyprock into the window opening?

Any openings in a rated assembly must follow suit. The door/window would have to be fire rated as well. Example: Typically a 1hr rated partition requires a 20 minute fire rated door. So to answer, you need to keep the fire rating across the board.

 

[RLGA]

Hi, I have another (maybe dumb) question I've never really quite understood. In the condition where a floor assembly is required to be a 'fire separation' with a fire resistance rating', and the supporting structure of load bearing walls, columns, and arches are required to have an equivalent 'fire resistant rating', does that mean that un-rated openings are not permitted in the load bearing wall? ie: can you have an un-rated window in an exterior load bearing wall that is required to have a fire resistance rating? Seems like the window or door is a weak point. If the intent is to just protect the structure, do you have to wrap 5/8" gyprock into the window opening?

I would have to review the specific wording within the NBCC, but fire-resistance-rated supporting construction under the IBC is just that: fire-resistance-rated construction. It is not a fire-resistance-rated assembly, which includes opening and penetration protection. The difference lies in the role of the supporting construction--it supports a fire-resistance-rated assembly to keep the assembly in place for a specified period of time, but it is not intended to limit the spread of fire from one area of the building to another.

 

[XE1805]

I would have to review the specific wording within the NBCC, but fire-resistance-rated supporting construction under the IBC is just that: fire-resistance-rated construction. It is not a fire-resistance-rated assembly, which includes opening and penetration protection. The difference lies in the role of the supporting construction--it supports a fire-resistance-rated assembly to keep the assembly in place for a specified period of time, but it is not intended to limit the spread of fire from one area of the building to another.

Ok thanks, that seems to be consistent with the NBCC. Assuming openings are permitted and the wall only requires a fire resistant rating, the last thing that is not clear to me is how to detail the openings in order to protect the structure - for instance in a wood framed load bearing wall, does the jamb or buck of the window opening need to be full drywalled out to the exterior sheathing before the window can be installed? The intention being to 'protect' the exposed wood on the interior of the rough opening. Seems like an odd condition.

 

[RLGA]

Ok thanks, that seems to be consistent with the NBCC. Assuming openings are permitted and the wall only requires a fire resistant rating, the last thing that is not clear to me is how to detail the openings in order to protect the structure - for instance in a wood framed load bearing wall, does the jamb or buck of the window opening need to be full drywalled out to the exterior sheathing before the window can be installed? The intention being to 'protect' the exposed wood on the interior of the rough opening. Seems like an odd condition.

The char rate for solid wood is about 1.5 inches per hour. Thus, if two 2x studs are provided around openings (which is typical), there should be sufficient protection for a 1-hour wall. If a two hour rating is required, three 2x studs around openings would be enough.

 

[tmurray]

RLGA is spot on.

Some people still choose to wrap door openings with fire rated gypsum. Talk to your AHJ and they can give an indication of what they will/will not accept.

 

[tmurray]

Any openings in a rated assembly must follow suit. The door/window would have to be fire rated as well. Example: Typically a 1hr rated partition requires a 20 minute fire rated door. So to answer, you need to keep the fire rating across the board.

Typically 45 minutes required in Canada. There are some situations where it can be reduced to 20 though.

 

[XE1805]

Thanks everyone, really useful info -

 

[Inspector Gadget]

Final building will likely be just over 600sm in building area.

This helps a tonne (note Canadian spelling ) because now a designer (architect) has to be involved, and an engineer for the structural stuff. Presumably one of those professions will be able to provide the code evaluation (matrix), building classification, F/S required, etc.

thanks, given the areas and construction type, I believe the building would be under 3.2.2.76 for major occupancy with 3.2.2.53 minor so this is all making sense -

Make sure that the renovation/addition only creates ONE residential suite. There's a limit on one residential unit in a building with an F2 major occupancy. I suspect you know that, but.... without going into details, there is/was a file where there was an intent/possibility/desire to take a one-unit-above-an-F2 into "gosh, this *is* a large space, we could go with two apartments, you know...."

Hi, I have another (maybe dumb) question I've never really quite understood. In the condition where a floor assembly is required to be a 'fire separation' with a fire resistance rating', and the supporting structure of load bearing walls, columns, and arches are required to have an equivalent 'fire resistant rating', does that mean that un-rated openings are not permitted in the load bearing wall? ie: can you have an un-rated window in an exterior load bearing wall that is required to have a fire resistance rating? Seems like the window or door is a weak point. If the intent is to just protect the structure, do you have to wrap 5/8" gyprock into the window opening?

The way I've dealt with this is that the opening in an exterior wall requiring a fire-resistance rating (but is NOT required to be a fire separation) need not have a fire-rated closure. Since the closure doesn't need to be fire-rated, the surrounding assembly need not be fire rated.

Actually, a reasonable example of this is a situation where a client created an opening in a wall that had been a fire-separation to isolate two suites, and create a one-suite restaurant, where the former second suite became a kitchen. There was extensive discussion with a bunch of folks - including the fire inspector - about wrapping the revealed studs. If the wall were just a demising wall separating two suites, no problem. Turns out the wall was also a load-bearing element supporting a fire-rated floor, so as far as I was concerned, the exposed wood *did* require some treatment with type X drywall.

One of the "oh crap I wish I'd realized that sooner" issues I ran into was the difference between an assembly required to have a fire-resistance rating, and a fire separation with a fire-resistance rating. Sometime last year, I had a situation - and I wish I could remember the details - where a pipe going through a rated floor did not need to be fire-stopped because the floor was a fire rated assembly but not a fire separation. Might have been with a mezzanine, since they're often required to have a fire-resistance rating, but not necessarily constructed as a fire separation. I know that each time this situation comes up, I have to read the code for the specific situation (fire stopped? tightly fitting allowed? No requirements at all?).