R occupancy separtion on the same lot

[Otter]

HI all,

Long time lurker, first time poster – wondering if I can get some advice here;

2018 IBC

Given two new R-2 buildings on one lot – 10’ between the facing exterior walls. Both VB construction, 2 story, and each one is 3000 sqft. Each is non-sprinklered due to state amendments. One could put a FSD line between the two and require 1 hour exterior walls and limited openings per Tables 602 and 705.8.

However, suppose I consider both buildings as one providing that the aggregate areas and overall building height complies with the height and area requirements of Chapter 5 for the most restrictive construction type and occupancy. Per 503.1.2, the area, height and construction type is ok and 705.3 Ex 1 will eliminate the exterior wall and opening protection. So, with these sections, both walls are unrated and there’s no FSD.

So far so good, but I go to Section 420 and see the dwelling unit separation requirements. I’m treating this as “one” building now so does this section apply? Do those exterior walls need to be rated/limited openings after all?

 

[cda]

We welcome Lurkers also.

 

[cda]

Some thoughts, not sure if it answers your question

Give it a day or two for great answers

How to count buildings on same lot

IBC 503.1.2 503.1.2 Buildings on same lot. Two or more buildings on the same lot shall be regulated as separate buildings or shall be considered as portions of one building if the building height of each building and the aggregate building area of the buildings are within the limitations of...

www.thebuildingcodeforum.com

 

[Glenn]

No, but I presume someone will read "words in a book" and disagree.

FSD is to keep entire cities from burning down. The idea of calling two buildings "one building" is only for the sake of discussing FSD and not burning down cities.

The intent of dwelling unit separation is to provide sufficient containment to a fire origin such that all occupants in the same physical building can egress before the building is overcome with fire.

I'd say from a dwelling unit safety perspective, the building is less hazardous as two actual buildings.

I would never consider mixing these two, but I am certain there will be disagreement.

 

[mtlogcabin]

Each is non-sprinklered due to state amendments.

If you want to consider them one building then IMHO the state amendment for not requiring sprinklers would not apply if there will be 5 or more total dwelling units in the two buildings. Some siding materials require a 10 ft minimum separation distance.

1403.12.2 Fire separation distance.
The fire separation distance between a building with polypropylene siding and the adjacent building shall be not less than 10 feet (3048 mm).

 

[Otter]

Thanks for the responses! I did bat around the sprinkler requirement so I'll still need to wrestle with that, but for me it ends up coming back to how far does one take the one building concept – does the now aggregate building need connected smoke detectors for example? Or simply figure 503.1.2 just addresses area, height and type and 705.3 just refers to exterior wall ratings and that is that -occupancy separations are irrelevant between the two but not within.

 

[mtlogcabin]

503.1.2 Buildings on same lot.
Two or more buildings on the same lot shall be regulated as separate buildings or shall be considered as portions of one building where the building height, number of stories of each building and the aggregate building area of the buildings are within the limitations specified in Sections 504 and 506. The provisions of this code applicable to the aggregate building shall be applicable to each building.

This is where I think the state or local AHJ could say the ARM's exception for sprinklers would not be applicable

 

[Glenn]

Some siding materials require a 10 ft minimum separation distance.

1403.12.2 Fire separation distance.
The fire separation distance between a building with polypropylene siding and the adjacent building shall be not less than 10 feet (3048 mm).

I don't recall having seen this one before. Thanks. I'm annoyed they used the phrase "fire separation distance" and then state it as between buildings. I realize is is not in italics and thus not meant to be per the definition, but the use of italics is a mess in the I-codes and not accurate. Had I learned this about two days ago I would have submitted a Group A proposal to change the term to simply "distance" and reduce confusion. Oh well, three years from now... ha, ha!

 

[mtlogcabin]

As someone on here once said ICC does not mean Intelligent Clear or Concise. That's why the BO gets paid the big bucks to try and make sense out of some of the language

 

[Otter]

Ha, ha, "ICC does not mean Intelligent Clear or Concise". I'm going to be using that one here on out. Thanks again for the info guys.