Robert
REGISTERED
At the risk of generalizing, am I correct that ANY building with a residential occupancy cannot be analyzed for nonseparated occupancies? I am referring to CBC 508.3.3 exception 2. Thank you.
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Non-separated occupancies
- Thread starter Robert
- Start date
No, the exception just means that residential occupancies can be considered within a nonseparated occupancy, but the “nonseparation” does not eliminate the requirement to provide separations required between dwelling/sleeping units and between dwelling/sleeping units and other areas of the building.
The main difference is that the dwelling/sleeping unit separations are only required to be fire partitions for walls compared to fire barriers for occupancy separations per Section 508.3, and the horizontal assemblies separating dwelling/sleeping units do not need to comply with the supporting construction requirements if of Type IIB, IIIB, or VB construction.
The main difference is that the dwelling/sleeping unit separations are only required to be fire partitions for walls compared to fire barriers for occupancy separations per Section 508.3, and the horizontal assemblies separating dwelling/sleeping units do not need to comply with the supporting construction requirements if of Type IIB, IIIB, or VB construction.
Robert
REGISTERED
Thanks. Separation is still required even though the cover sheet can call it nonseparated, just that the separation is less restrictive.
Correct. No separation required per Table 508.4, but separation required per Sections 420.2 and 420.3.
Robert
REGISTERED
Thanks....starting at section 420.3, it leads me to section 711.2.3. Per this section, exception 2, there is no requirement for supporting construction to be rated if VB construction.... But the wording of the exception states "horiz. assemblies at the separation of dwelling units as req'd. by sect. 420.3". So my question is: If the horiz. assembly was separating office (ground floor) from dwelling unit (floor above), can the supporting construction still be unprotected? Or is the exception just for two dwelling units?
This is most important because if the supporting construction needs to be rated, so do the windows, which will then need to be steel, which would not match the existing Victorian wood windows on the 2 floors above.
This is most important because if the supporting construction needs to be rated, so do the windows, which will then need to be steel, which would not match the existing Victorian wood windows on the 2 floors above.
The exception states "separation of dwelling units..." and not "separation between dwelling units..." The requirement is the separation of dwelling units from other dwelling units and "other occupancies contiguous to them," which would include the office below per your example.
By the way, if the supporting construction would have been required to be rated, that would not require the windows to have a rating. Windows do not support anything--only the load-bearing walls and columns would be supporting the horizontal assembly.
By the way, if the supporting construction would have been required to be rated, that would not require the windows to have a rating. Windows do not support anything--only the load-bearing walls and columns would be supporting the horizontal assembly.
Robert
REGISTERED
Most helpful! "of" vs. "between".
Now, to close the loop on this thread, you said even if we did need supporting construction, the openings would not need to be rated, which confuses me. Table 716.6 states windows in a required wall assembly having various ratings (ie: 1 hour) need minimum fire window ratings (ie: 3/4 hour). What say you?
Now, to close the loop on this thread, you said even if we did need supporting construction, the openings would not need to be rated, which confuses me. Table 716.6 states windows in a required wall assembly having various ratings (ie: 1 hour) need minimum fire window ratings (ie: 3/4 hour). What say you?
The requirement states that horizontal assemblies are required to be supported by "construction" having a rating equal to (or greater than) that of the horizontal assembly. It uses the word "construction" and not fire walls, fire barriers, etc., which are "assemblies" that require opening protection per Tables 716.5 and 716.6.
To illustrate this, Section 602.1 and Table 601 requires the various construction types to have fire-rated "construction" where required and at the ratings indicated. For example, Type IIIA requires 2-hour exterior bearing walls--that means the wall construction is required to have a 2-hour rating, but the openings do not need to be protected unless protection is required per Section 705.8. For interior bearing walls of Type IIIA construction, the required rating is 1-hour, but again that is for the wall construction--openings are not required to be protected unless the wall also serves as an assembly (i.e., fire wall, fire barrier, fire partition, or smoke barrier) required by another section of the code as stated in the last sentence of Section 602.1.
To illustrate this, Section 602.1 and Table 601 requires the various construction types to have fire-rated "construction" where required and at the ratings indicated. For example, Type IIIA requires 2-hour exterior bearing walls--that means the wall construction is required to have a 2-hour rating, but the openings do not need to be protected unless protection is required per Section 705.8. For interior bearing walls of Type IIIA construction, the required rating is 1-hour, but again that is for the wall construction--openings are not required to be protected unless the wall also serves as an assembly (i.e., fire wall, fire barrier, fire partition, or smoke barrier) required by another section of the code as stated in the last sentence of Section 602.1.
Robert
REGISTERED
Amazing..."construction" vs. "assembly". Thank you for your insights. Unless I've missed something in this VB example, the upstairs dwelling unit needs the rated horizontal assembly protection from the office below, needs fire partitions at common walls to the office, and it's supporting walls/posts need 1 hour protection with the openings excluded (unless distance from property line becomes an issue).