# Can a "wall" have offsets?

Where openings are allowed or need to be protected for a certain percentage of the length of a wall (705.8 openings relative to property line, 707.6 openings in fire barrier walls), what happens if the wall has small offsets in plan?  Does each segment need to be counted as a separate wall?

Suppose the offset is 3 inches?  12 inches? What if it is 3 feet? Suppose there is an alcove for a recessed door?  The door could be nearly 100% of the recessed wall, but only 2% of the exterior building dimension.

If this is addressed in the CBC, please tell me where to find it.  I can't find it anywhere!

Original Post

Fire separation distance is measured perpendicular to the wall, essentially the walls that are not facing a property line (presuming they are perpendicular to property line) technically are not required to be fire rated and their area does not count toward the allowed openings based on fire separation distance. The IBC commentary has very good explanations and examples. You can get the commentary online at ICC.

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Thank you for your answer, but that is not my question.  Perhaps an illustration will help.

Here's a simplified illustration.  Wall A is 40' long and has no openings.  It is 6' from the property line.  Wall B is 10' long and has 100% openings, which is not permitted.  Can I combine walls A and B in computing the percentage of windows?  If so, I have 20% windows, which do not need to be protected in a sprinklered building per 708.5.

Does it matter how large the offset is between walls A and B?

The same question applies to the occupancy separation wall.  Can I combine the two walls when computing the percentage of openings? If so, is there a limit to the amount of offset I can have and still combine the walls?

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rmuller:

Using your diagram, Wall A and Wall B would be considered as one wall, especially since they are within the same distance range used in Table 705.8. As Jim mentioned, the small offset walls are not included in the applicable wall area, since they do not face the lot line.

For fire barriers, the total length of wall shared between the two adjoining spaces are considered, including the offsets.  Therefore, the 25% is applied to the sum of the lengths of Wall C, Wall D, and the little offset wall portion.

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Thank you, this is useful.  I assume for the property line wall, we would give the entire wall the same setback as wall "A".

In case the AHJ doesn't agree, is there anything I can point to in the code to bolster this?  Or a published code interpretation somewhere?

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here are pertinent pages from the ICC code commentary

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