For a 3-story CLT building: Type V or

[nealderidder]

I'm designing a 3-story life science lab building (B occupancy) that will be constructed of CLT. It's not a big footprint (18,000 SF) and a Type V-B gives me the height, stories, and area I need. There are benefits to not using a Type IV (mostly fire ratings) but are there any downsides to using V-B?

For instance - The required Fire Flow (CFC appendix B) for a type V-B is greater than other types. If Fire Flow is high enough you might need a water tank. But on this small of a building, the fire flow requirement (with allowed reduction) isn't any more that any other type.

Can you think of anything else, like fire flow, that selecting a Type V-B "costs" me? If I don't need it for height or area, what benefit is there to calling my building a type IV?

Thanks for any insights!

 

[Penguin87]

VB typically has the lowest allowable area, but the most permissive construction type (anything goes). We typically try to permit all construction as the most permissive type for the programmatic requirements balanced with allowing potential future additions.

 

[nealderidder]

VB typically has the lowest allowable area, but the most permissive construction type (anything goes). We typically try to permit all construction as the most permissive type for the programmatic requirements balanced with allowing potential future additions.

Agreed, why wouldn't you? But that's my question, is there any reason why not? Is there any downside to selecting the most permissive (like my fire flow example)?

 

[Penguin87]

Agreed, why wouldn't you? But that's my question, is there any reason why not? Is there any downside to selecting the most permissive (like my fire flow example)?

Yes, it may limit future expandability or change of occupancy in that the building area may exceed the area limitations. Ie, going from a B to A occupancy.

 

[nealderidder]

Yes, it may limit future expandability or change of occupancy in that the building area may exceed the area limitations. Ie, going from a B to A occupancy.

That's certainly something to consider, thanks.

 

[jar546]

Yes, it may limit future expandability or change of occupancy in that the building area may exceed the area limitations. Ie, going from a B to A occupancy.

Outside the codes from a marketing perspective, you may be limiting the value of the building to the owner for this exact reason above. Pay me now or pay me later is the saying that comes to mind.

 

[Jay Smith]

I could see choosing IIIB if you’re not planning to use untreated wood in the exterior walls. There are no fire ratings in IIIB, unless you have exterior bearing walls. You don’t need the extra height and area as compared to VB, but it’s there just in case.

 

[steveray]

Yes, it may limit future expandability or change of occupancy in that the building area may exceed the area limitations. Ie, going from a B to A occupancy.

This^^^^^^^^^^^^^^^^^^^ I have had a customer "derate" a IIB PEMB because they wanted to build the interior offices out of wood but told them it would limit future additions.....