• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

How to count buildings on same lot

This has been quite interesting to follow and has usual brudgers comments can make us think and dive deep into our thought process. Sometimes we tend to go to deep.

Here is my take

Chapter 5 controls height and area of buildings period

501.1 Scope.

The provisions of this chapter control the height and area of structures hereafter erected and additions to existing structures.

503.1.2 Buildings on same lot. Simply states you have to meet the requirements of Table 503 Sections 504 and 506

The provisions of this code applicable to the aggregate building shall be applicable to each building. Does not mean the existing building needs to meet today’s code. The existing building and the new building need to be compatible as one. A type II existing building and a Type V new building would have to be considered as a Type V building. If the existing building got a frontage increase for all 4 sides then it would have to be re-evaluated as one building. Same if the existing got an increase for sprinklers the new building would have to have sprinklers.

Same with occupancy types. The most restrictive applies to the height and area limits.

Even if you believe a new building under 503.1.2 is an addition under Chapter 34 you are only required to comply with Chapter 5

3403.1 General.

Additions to any building or structure shall comply with the requirements of this code for new construction. Alterations to the existing building or structure shall be made to ensure that the existing building or structure together with the addition are no less conforming with the provisions of this code than the existing building or structure was prior to the addition . An existing building together with its additions shall comply with the height and area provisions of Chapter 5.
 
And I'm beginning to think that it doesn't matter a whole lot whether you call it an addition or not, anyway. The IEBC says that a fire area that is increased by an addition shall comply with CH9 IBC, so call it an addition all day long, but you're going to have to sprinkler it now if you bust fire area.
 
A new building next to an existing building would be 2 different fire areas

[F] FIRE AREA. The aggregate floor area enclosed and bounded by fire walls, fire barriers , exterior walls or horizontal assemblies of a building. Areas of the building not provided with surrounding walls shall be included in the fire area if such areas are included within the horizontal projection of the roof or floor next above.

Could happen depending on occupany type and fire area size. Don't DP's use fire areas to avoid sprinklers?
 
mtlogcabin - I would agree that normally a fire area would be defined by the exterior walls of a building. However, in this case we are combining several structures into one building. Therefore in this case the exterior walls of all the combined structures establish the fire area. One of the reasons I used both "structure" and "building" in my previous posting was that I was trying to differetiate between individual structure that were being combined to create the new building area. Hopefully this makes some sense and will help to explain my previous post if it caused confusion instead of providing clarity as I had hoped.
 
righter101 said:
IBC 503.1.2...This allows separate buildings to be considered as a single building.

Question: if I have say, a dozen "B" occupancies on the same property and am putting a new building, also a "B" in close proximity to two of the existing structures (these are all 800-1500 sq ft), can I group 2 or 3 of them together and consider it a "single" structure under the 503.1.2 provisions, then consider all the others separate, or do I need to consider all the buildings on the property if I am going to use this???

I have my idea but wanted to get feedback and opinions.
Click to expand...
My opinion and last post: I find Chapter 34 useful and applicable when working with existing buildings, but understand that compliance with the new construction provisions is always an option for the DP. In the event you would need to consolidate the number of buildings on a lot (i.e., per zoning) without fire-rating exterior walls, addding occupancy separations, and/or sprinkler systems for area increases in order to add another building to a lot, and not wanting to do a lot split, one could use the following code provisions as a means to answer the OP question:

501.1 Scope. The provisions of this chapter control the height and area of structures hereafter erected and additions to existing structures.

Addition. An extension or increase in floor area or height of a building or structure.

503.1.2 Buildings on the 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 height of each building and the aggregate area of buildings are within the limitations of Table 503 as modified by Sections 504 and 506. The provisions (Chapter 34 is an applicable provision of this code for the existing buildings and the area(s) beings added to it.) of this code applicable to the aggregate building shall be applicable to each building.

Table 503

B Occupancy, V-B construction. Allowable area without increases shall not exceed 9,000 square feet and 2 stories.

Three existing 1,500sf buildings, four existing 800sf, and one new 1,500sf building lumped together to form one single building would exceed the 9,000sf. 504.2 automatic sprinkler system increase would be required in existing building alteration. The new building being added to this single building grouping would then qualify as an addition to existing buildings, thereby giving the designer the option to use Chapter 34. This is not a wrong way to design multiple buildings on a single lot as a single building, merely an option available to the DP.

3409.5 Additions. Provisions for new construction shall apply to additions. An addition that affects the accessibility to, or contains an area of, a primary function shall comply with the requirements in Section 3409.7.

3410.2 Applicability. Structures existing prior to (DATE), in which there is work involving additions, alterations, or changes of occupancy shall be made to conform to the requirements of this section or the provision of Section 3403 through 3407. The provisions in Sections 3410.1 through 3410.2.5 shall apply to existing occupancies that will continue to be, or are proposed to be, in Groups A, B, E, F, M, R, S and U. These provisions shall not apply to buildings with occupancies in Group H or I.

3410.2.1-3410.2.5 cover change of occupancy, partial change of occupancy, additions, alterations and repairs, and accessibility requirements.

3410.6 Evaluation process has alternate methods for evaluating existing buildings that would not normally comply with Chapters 2 through 12 and 14 through 33, and prescribe compliance alternatives. This could be an applicable and useful section when combining multiple existing buildings with new construction to form a single building on the same lot.
 
Big Mac

I understand your logic but by Chapter 14 definitions of exterior wall, wall covering and wall envelope you would still have an exterior walls on each structure which meet the definition of fire area.

This has been a good post and if others have an opinion please chime in
 
Three existing 1,500sf buildings, four existing 800sf, and one new 1,500sf building lumped together to form one single building would exceed the 9,000sf. 504.2 automatic sprinkler system increase would be required in existing building alteration. The new building being added to this single building grouping would then qualify as an addition to existing buildings, thereby giving the designer the option to use Chapter 34. This is not a wrong way to design multiple buildings on a single lot as a single building, merely an option available to the DP.
Click to expand...
504.2 is for height increase 506 allows frontage increase if needed and/or sprinkler increase to make the aggregate area work for the 2 structures.
 
To come back to my devilish advocacy.

In the situation described in the original post, the premise is the treatment of the existing buildings on the same lot as a single building is only an existing condition if such an option was code compliant at the time they were constructed.

I.E. the reason that multiple buildings are allowed to be treated as a single building in the current code is based on the assumption that the buildings meet the current code.

If the code underwhich the buildings were built did not allow multiple buildings to be treated as a single building, then the single building is not grandfathered in even if each building considered individually would be.

That is why the devil possessed me to suggest that you get one original building which is grandfathered, and then any buildings which are joined with it in the process of creating a single "virtual" building are additions, irrespective of their being existing or not.

To take an obvious example of why this is problematic, consider the case of R2 occupancy where the existing buildings are unsprinklered. Now a new building is placed among them without meeting current fire separation standards...

...even though the aggregate area for R2 buildings increased when sprinkler systems for R2 occupancies became required in the 2003 code cycle.

In other words, the current area limitations are based on the condition that the construction meets current code - while the fire separation requirements are based on the idea that nearby buildings do not.
 
mtlogcabin said:
A new building next to an existing building would be 2 different fire areas[F] FIRE AREA. The aggregate floor area enclosed and bounded by fire walls, fire barriers , exterior walls or horizontal assemblies of a building. Areas of the building not provided with surrounding walls shall be included in the fire area if such areas are included within the horizontal projection of the roof or floor next above.

Could happen depending on occupany type and fire area size. Don't DP's use fire areas to avoid sprinklers?
Click to expand...
And I agree completely. Because it IS a building next to a building. I was just using the illustration to show that it is in fact a building next to a building, and not an addition.

Another thing a lot of people overlook regarding 503.1.2, is that you can break the groups of buildings up any way you please; examples:

As the architect, I might decide to assume a property line between two 1500 sq ft buildings that are two feet apart, and consider two buildings that are separated by a mile an aggregate building. I may choose to do this because of planned future construction, exterior walls that make it convenient, or just because I'm in the mood. And 503 doesn't tell me HOW to do it, it just says I can consider them separate BUILDINGS, or an aggregate BUILDING.

And new construction may or may not have a thing to do with it. I could go into the building department with a site plan, with no construction planned whatsoever, and tell them that I am submitting a request to make 3 existing, separate 500 sq ft buildings an aggregate building, or I may submit a permit to build 3 new 500 sq ft buildings and consider them an aggregate building. The code doesn't care, as long as I meet the criteria in 503 for multiple buildings on the same lot. in both of the above cases, the code simply recognizes the arrangement as an aggregate building, not 3 buildings, nor a building with additions.
 
Last edited by a moderator:
brudgers said:
In other words, the current area limitations are based on the condition that the construction meets current code - while the fire separation requirements are based on the idea that nearby buildings do not.
Click to expand...
And I would argue that it doesn't matter. As the designer, the choice is yours. If the new building complies with current code and the old one does not, assume a property line between them, rate exterior walls appropriately if necessary, and do nothing else with the old building. Conversely, if you want to consider them an aggregate building on the same lot in terms of allowable height and area, you are free to do so. Simply apply the code requirements for an aggregate building to each of the separate buildings.

I would also disagree that fire separation requirements are based on the premise that the existing building doesn't meet current code. The code is happy to allow deletion of fire separation if both buildings meet current code. That's what 503.1.2 is all about.

Even if you maintain a position that 34 or IEBC applies, even they do not allow willy-nilly construction of adjacent buildings that do not meet current code. Increase of fire areas would require mitigation just as compliance with 503 would.
 
Last edited by a moderator:
If you can put an "imaginary roof" (much like the imaginary property lines) over all the buildings and aggregately the "one" building meets all the code requirements (which could be the case, since these are apparently small buildings), I don't believe you need to consider the buildings separately.
 
What if the existing building on the same lot as the proposed new construction is a foot below base flood elevation, or not accessible enough, or not painted pretty? The existing building may not meet 'current code', but does it have to be reviewed for anything other than area and height, type and use under Chapters 5, 6 and 7?
 
imhotep said:
What if the existing building on the same lot as the proposed new construction is a foot below base flood elevation, or not accessible enough, or not painted pretty? The existing building may not meet 'current code', but does it have to be reviewed for anything other than area and height, type and use under Chapters 5, 6 and 7?
Click to expand...
Chapter 34 and IEBC as applicable.
 
imhotep said:
What if the existing building on the same lot as the proposed new construction is a foot below base flood elevation, or not accessible enough, or not painted pretty? The existing building may not meet 'current code', but does it have to be reviewed for anything other than area and height, type and use under Chapters 5, 6 and 7?
Click to expand...
You are not REQUIRED to consider them as an aggregate building. That is only one option that's there if it suits your situation. If, when considered as an aggregate, the modifications would be too expensive or troublesome, the code allows you to simply assume a property line and consider them as two buildings, as is most often the case.
 
brudgers said:
Yes, it is one or the other.
Click to expand...
No, the scoping provisions of neither apply in this case.

That is, unless you make up code and call it an addition, which it is clearly not.

You have to play by the rules, and follow the code. You're not allowed to make up your own rules.

Of course, you could always try to change the code or request a local amendment.
 
Here, Brudgers, I'll even do your work for you. Just trot down to the next code change hearings and hand this to them.

I'll let you pen the rationale...

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 height of each building and the aggregate area of buildings are within the limitations of Table 503 as modified by Sections 504 and 506. The provisions of this code applicable to the aggregate building shall be applicable to each building.

When a new building is to be constructed on the same lot as an existing building and is to be considered an aggregate building, the provisions of this code for the aggregate need not be applied to each building, but may only be applied to the new building. The existing building, shall be subject to the International Existing Building Code.
 
texasbo said:
The provisions of this code applicable to the aggregate building shall be applicable to each building.
Click to expand...
The provisions of this code applicable to the aggregate building shall be applicable to each building.
 
Texasbo, please help me understand this. 503.1.2 was added to the code to address an inconsistancy in the code where two buildings within 10' of each other would need to fire-protect their adjacent exterior openings/walls based upon the imaginary property line and fire separation distances, however if they were connected by a roof or wall, and their aggregate area was still under the allowable areas, they would then be considered an addition and would not require fire-protection of those interior walls. My understanding is, for consistency sake, you either consider it one building under 503.1.2, or you consider it two buildings. You don't get to consider it as one building for allowable areas and then default back to it being two separate buildings. You make the choice of how you want to handle because there are benefits to each way, and then you treat as such per the code regarding your choice. If you take an existing building, and want to ADD a building to it, whether it is 2' or 20' away, and consider them as one building, then you treat the new part as an addition (Chapter 34/IEBC can then be applied if necessary, for example if the existing building were to experience a change in occupancy, or did not meet the type of construction or structural requirements for new construction of the current code when the new building is added). If you want to build an new building next to an existing building and maintain them as separate, then you treat them as such and fire protect the exterior walls/openings per the code.

In other words, adding a building to a lot with an existing building, and wanting to consider it as one building, requires that it be treated as a single building when applying the code. This is not pulling a rabbit out of a hat. It is fundamental difference of interpretation, and I do not believe yours is entirely consistent with the code, by definition. You have not convinced me otherwise, and I do not see the rational for applying 503.1.2, calling it a single building to avoid fire protection of exterior walls, and then reverting back to separate building application of the code. In the words of the great and almighty Spock, 'That is illogical sir."
 

Applying Chapter 34 or the IEBC does not automatically require the existing building to comply with todays code. An evaluation would need to be done.

INTERNATIONAL BUILDING CODE

​
CHAPTER 34

​
EXISTING STRUCTURES

​
SECTION [EB] 3410.2.3

​
Reference IEBC Section 1301.2.3

​
IEBC Interpretation No. 43-062006 EditionIssued: 11-07-2006

​
BU_06_56_06

​
[EB] 3410.2.3 Additions. Additions to existing buildings shall comply with the requirements of this code for new construction. Thecombined height and area of the existing building and the new addition shall not exceed the height and area allowed by Chapter 5. Wherea fire wall that complies with Section 705 is provided between the addition and the existing building, the addition shall be considereda separate building.

​
! ! ! ! ! ! ! ! ! !

​
Q: Is an addition to an existing building subject to the requirements of the International Building Code for newconstruction if the existing building including the new addition complies with the mandatory safety scores required inSection 3410 of the International Building Code?

​
A: Yes. New construction, including additions to existing buildings and/or alterations to existing buildings, must complywith the provisions of the International Building Code. In addition to the International Building Code, new construction isalso subject the provisions of all International Codes to the extent mandated by the authority having jurisdiction, suchas the International Fire Code, International Plumbing Code, International Mechanical Code, International Fuel Gas Code,International Energy Conservation Code, etc.

​
_______________________________________________________________________________________________

 
I agree with texasbo. I have no idea why Chapter 34 or the IEBC would be in play. You are evaluating all buildings on a single lot OR providing proper fire separation distance by lot lines, imaginary or real, individual or clustered, between buildings. To prevent conflagration, maybe?

From the sound of some of the responses, I suppose you're only limited by how much the client is willing to see destroyed.
 
You must log in or register to reply here.
Top