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Typically, ...masonry flying buttresses are a structural component
that assists in supporting the weights of the structure [ i.e. - walls
& roofing systems ].

< &
 
The construction type will depend on the fire rating, which depends on the thickness of the concrete cover over the reinforcing.

The structural drawings should also show whether the roof framing forms a 3-hinged arch, in which case the buttresses might be decorative, or if the roof imparts an outward thrust, in which case the buttresses are structural.

If the roof is flat there is no thrust, but the buttresses might still be structurally necessary to resist wind or seismic loads.

We need a lot more information to be able to answer your question.
 
I'm trying to have a better understanding of type 1a (protected) vs 1b (unprotected). If it's steel, it's coated with fire resistance materials or not. If it's all concrete/masonry, do we assume it's protected? And if the buttresses are structural, does it affect the type of construction?
 
Are you a builder, design professional, code official, or other?

IBC section 722 has information on minimum wall & slab thickness, cover over reinforcing, etc. for different fire ratings. The lesser of the rating based on thickness vs. cover would apply. "Restrained" for the purposes of cover (Table 722.2.3(1)) means whether thermal expansion under fire conditions is limited, and not the usual structural engineering sense of restrained.

 
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