Everything you say is correct, except you're still using the word "addition", which is not the subject of 503.1.2.Papio Bldg Dept said: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."
I absolutely agree that you can consider multiple buildings as a single building, to get the benefits of 503.1.2. However, it is just that, a single building, not multiple buildings, and not a building with additions.
The intent of 503.1.2 is to not penalize multiple buildings that are close together if they could have been a single building under one roof. You are right, it would be ridiculous to require rated exterior walls, etc, between three 500 sq ft buildings, when one 1500 square foot building would be just fine. However, it is not the intent of the code to allow you to only make part of this "single building" comply with the code.
If that were the case, a wiley architect could design one building, then come in the next day with plans to put another one right beside it, and claim that he would have to do nothing to upgrade the original building that just got co'd the previous day.
You have a choice: consider them separately, or pretend they are all a single building. In the first case, you assume property lines between the buildings, and you need not modify the existing buildings (unless of course the property line is too close to an exterior wall). In the second case, you review all three buildings as if they were a single building. You don't get to mix and match. In other words you don't get to consider it a single building, but make only part of it comply.
To beat the dead horse: read 503.1.2 again - it says that you can consider them as separate buildings or as one building. The key word is building. There is no "addition" anywhere in this very specific section of the code. One member planted that seed, and a couple of you have picked up on it, but it's just not there.
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