Non-Combustible Roof Deck

[Francis Vineyard]

3B type construction; 3 stories R-3Architect submitted RDP sealed drawings for full length shed dormer with full width glazing 10’ height and door opens onto Cumaru wood deck surrounded with a 36” high guard wall.Plans show the new wood framed walls and guard with cement boards on the exterior side and wood panels interior. Do the framing in the new wall that’s practically all glass and the guard walls need to be either 2B (FRT wood) or solid masonry, even though is supporting construction is combustible?Do the guard need to be 42”?

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[texasbo]

Technically, in my opinion, I don't think there is any way to get around the requirement of noncombustible or FRTW on the exterior wall framing, and in fact, if it's carrying enough load to be a bearing wall, must be 2 hr rated.

In my opinion, a guard is not an exterior wall, and certainly wouldn't need to comply with the requirement for Type III exterior walls.

Would like to see other's thoughts.

 

[Examiner]

Agree Type III-B's exterior walls are to be non-combustible. FRTW does not comply with ASTM number to be classified as non-combustible. For some reason many of my fellow Architects do not know this. They only teach design in school not codes. The glazing I am sure is not a bearing wall system. The guard, as mentioned, is not required to comply with being non-combustible. In the 2006 IBC 1013.2 Exception 1 allows guard heights to be between 34 to 38 inches when serving as a stair handrail. So if it is not serving as a stair’s handrail system it must be 42-inches high.

 

[texasbo]

Examiner - Type III allows noncombustible material OR FRTW in exterior walls.

 

[Examiner]

Sorry I missed the last part of the section's sentence "2-hour rating or less". Got to get an eye appointment soon. Glasses are scratched and due for yearly checkup anyway.

 

[Francis Vineyard]

As always appreciate the input and keeping it straight

Thanks

 

[peach]

Why would someone classify a 3 story R3 as Type III anyway?

602.1.1 gives the minimum requierments... "a building or portion thereof shall not be required to conform to the deatils of a type of construction highter than that type, which meets the minimum requirements based on occupancy even though certain features of such a building actually conform to a highter type of construction". I've always been taught that regardless of what the designer says it is.. if it CAN be Type V, it's type V.

 

[Examiner]

Yes, building area is based on the minimum construction type the building could have. However, one may want to have the building classified as the Construction Type the building is actually built with. If it is recorded somewhere then if ever an addition is planned there is documented evidence, hopefully with the AHJ, of its actual construction type. We architects cannot just tear into a building with destructive investigation to determine the possible construction type. We are still assuming the Construction Type. It should be documented with the AHJ just for future expansions. If it is documented on a minimum type of construction and not the actual construction type then a planned addition may not ever be able to occur.

 

[steveray]

Yes, building area is based on the minimum construction type the building could have. However, one may want to have the building classified as the Construction Type the building is actually built with. If it is recorded somewhere then if ever an addition is planned there is documented evidence, hopefully with the AHJ, of its actual construction type. We architects cannot just tear into a building with destructive investigation to determine the possible construction type. We are still assuming the Construction Type. It should be documented with the AHJ just for future expansions. If it is documented on a minimum type of construction and not the actual construction type then a planned addition may not ever be able to occur.

EXACTLY!...we had a towing company that came in to put up a steel building, and they wanted to know if they could build the offices out of wood....we said yes but they would never be able to add on....(at the limit for VB)...keeping it IIB would allow them to double the size of the building at some point...cmae back with plans for steel framed offices and 1000 more square feet...