Stepped Building Fire Wall

[Mech]

2009 IBC

Can a stepped building fire wall terminate 30 inches above the upper roof per 706.6 instead of complying with section 706.6.1?

My scenario has an approximate 4 - 5 foot difference in roof heights.

Thanks in advance.

706.6 Vertical continuity. Fire walls shall extend from the foundation to a termination point at least 30 inches (762 mm) above both adjacent roofs.

Exceptions:

1. Stepped buildings in accordance with Section 706.6.1.

2. Not applicable to scenario

3. Walls shall be permitted to terminate at the underside of noncombustible roof sheathing, deck or slabs where both buildings are provided with not less than a Class B roof covering. Openings in the roof shall not be located within 4 feet (1220 mm) of the fire wall.

4. Not applicable to scenario

5. Not applicable to scenario

706.6.1 Stepped buildings. Where a fire wall serves as an exterior wall for a building and separates buildings having different roof levels, such wall shall terminate at a point not less than 30 inches (762 mm) above the lower roof level, provided the exterior wall for a height of 15 feet (4572 mm) above the lower roof is not less than 1-hour fire-resistance-rated construction from both sides with openings protected by fire assemblies having a fire protection rating of not less than 3/4 hour.

Exception: Where the fire wall terminates at the underside of the roof sheathing, deck or slab of the lower roof, provided:

1. The lower roof assembly within 10 feet (3048 mm) of the wall has not less than a 1-hour fire-resistance rating and the entire length and span of supporting elements for the rated roof assembly has a fire-resistance rating of not less than 1 hour.

2. Openings in the lower roof shall not be located within 10 feet (3048 mm) of the fire wall.

 

[Builder Bob]

Yes, as long as the fire wall terminates 30 inches above the lower roof and the wall has a one hour rating until the wall above reaches 15 feet. This would also in clude the limitations for openings as if a fire wall in this 15 foot section.

 

[Francis Vineyard]

Expanding on BB need to use 706.6.1 stepped building provisions with different roof heights.

Note provisions have been added to address firewalls adjacent to sloped roofs in the 2012 edition.

 

[my250r11]

IMO it is a stepped bldg. so has to meet 706.6.1 and can stop @ 30in. if it meets the requirements of 706.6.1 or the exception.

 

[Mech]

Thanks for the answers, but I did not convey things properly.

This is what I want to do . . . terminate the fire wall 30 inches above the upper roof and have nothing above it. The more I think about it, the more I believe this is acceptable. In my mind, it is no worse than having adjacent roofs at the same elevation.



I don't suppose I could do the following (without the dashed wall portion.) There is nothing above the higher roof and adding another 10 feet of one hour rated wall to meet the conditions of 706.6.1 Stepped buildings does not seem logical to me.



The exceptions under 706.6.1 are not desirable - fire rating around 15,000 sf of ceiling and structural steel.

 

[my250r11]

I believe you can do that as long as the lower roof has the one-hour FR for the entire length of the portion with out the parapet. But i bet someone besides me will chime in soon.

 

[RLGA]

If you use the stepped building method and stop the fire wall at the lower roof, then, as my250r11 stated, the exception to Section 706.6.1 will apply. The 1-hour extension need only extend up to 15 feet, but if the wall is not 15 feet high, then the entire wall above the lower roof will need to be rated 1-hour with protected openings.

If not using the stepped building exception of Section 706.6, then the fire wall will need to extend up to 30 inches above the upper roof, unless one of the other exceptions of Section 706.6 permits it to stop at the deck of the upper roof.

 

[Mech]

Thanks Ron,

Your response regarding the one hour rated wall for a stepped building is clearer to me than the code section.

BTW, I edited the first picture. It is humongous now, but it shows the condition in its entirety.