Existing Log Construction - 30min Horizontal Assembly

[thomasfagan]

I am looking into a change of occupancy for an existing 4000sf 2 story log building. Currently is B occupancy, and owner is looking to convert to a Hostel, type R-1. Location is in Oregon and applicable code is OSSC. It is clear that a sprinkler system will need to be installed and that sleeping rooms will need to need to separated from other sleeping rooms and occupancies by 30min fire partitions and horizontal assemblies. The walls are easy enough... the floors are harder to understand.

The 2nd level floor is currently 2x6 t&g decking over 8" dia logs at 4ft o.c. The beams themselves don't need to be protected per 711.2.3. It would be easy enough install new GWB under the t&g between the logs... but I dont think this would be considered "continuous". Can anyone suggest a code path that would allow the logs to remain exposed? Reference material and testing info for log buildings seems to be pretty sparce since it is a fairly niche building type.

 

[redeyedfly]

The beams themselves don't need to be protected per 711.2.3.

Those beams are part of your horizontal assembly, 711.2.3 does not exempt the log joists from protection but it does exempt the bearing walls supporting the logs.

I would use a char calc on the logs and the decking and ask your structural engineer if the floor still meets minimum design loads at the reduced size of the members after removing the char. I assume your client doesn't want to cover up all the wood.

 

[thomasfagan]

Those beams are part of your horizontal assembly, 711.2.3 does not exempt the log joists from protection but it does exempt the bearing walls supporting the logs.

I would use a char calc on the logs and the decking and ask your structural engineer if the floor still meets minimum design loads at the reduced size of the members after removing the char. I assume your client doesn't want to cover up all the wood.

Thanks for pointing out my misunderstanding of 711.2.3. I had thought about the char rate... but all the code references and reports I could find are specific to sawn lumber, glue lams, and other manufactured wood products. For example chapter 16 of 2018 National Design Specification (NDS) for Wood Construction does not appear to apply to Logs... anyway probably need to find a Log Building expert

 

[redeyedfly]

Thanks for pointing out my misunderstanding of 711.2.3. I had thought about the char rate... but all the code references and reports I could find are specific to sawn lumber, glue lams, and other manufactured wood products. For example chapter 16 of 2018 National Design Specification (NDS) for Wood Construction does not appear to apply to Logs... anyway probably need to find a Log Building expert

I would start with a fire engineer for an Engineering Judgement. Nearly all AHJs accept EJs for unusual existing assemblies. 30min should be relatively easy to justify for the engineer.