Building Type Classification

[dreamchaser69]

SFR = Group R-3
House is elevated on concrete pilings / all supporting exterior columns/beams are concrete
All floor systems are steel web trusses with 4.5" concrete topping
Stairs between floor levels are wood
NO interior load bearing walls - all loads carried on steel beams
All exterior walls are 12" thick ICF (8" core)
Exterior of exterior walls are covered in 3-coat stucco
All exterior decks are concrete and steel truss with underside covered in treated plywood then covered with stucco
Garage ceiling below is 5/8" type X gyp
Storage enclosure in garage is 5/8" type X gyp (for stair access / elevator)
Interior beams supporting the spans where needed are heavy red steel.
Interior columns supporting the red steel beams are also red steel
All undersides of floors/trusses are sprayed with fire-retardant spray foam - open cell polyurethane.
Interior ceilings is planned at 1/2" gyp but could be 5/8" or 5/8" type X if it makes a difference.
Interior walls are 1/2" gyp
Interior walls (all) are insulated with R-13 or R-19 fiberglass batts where appropriate for size
Interior of attic is spray foamed and then covered with radiant barrier
Roof trusses are made of fire-retardent treated wood, covered with 15/32 decking, covered with peel-n-stick barrier and metal standing seam roof (underside of roof is also spray foamed.

What is the proposed building classification?
What could it be?
What would make it better/tighter?
Would steel studs in the interior make a difference in classification?

[Jerry Peck - Codeman]

From the 2017 FBC-Building: (underlining is mine)
- 602.2 Types I and II.
- - Types I and II construction are those types of construction in which the building elements listed in Table 601 are of noncombustible materials, except as permitted in Section 603 and elsewhere in this code.
- 602.3 Type III.
- - Type III construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of any material permitted by this code. Fire-retardant-treated wood framing complying with Section 2303.2 shall be permitted within exterior wall assemblies of a 2-hour rating or less.
-602.4 Type IV.
- - Type IV construction (Heavy Timber, HT) is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of solid or laminated wood without concealed spaces. The details of Type IV construction shall comply with the provisions of this section and Section 2304.11. Exterior walls complying with Section 602.4.1 or 602.4.2 shall be permitted. Minimum solid sawn nominal dimensions are required for structures built using Type IV construction (HT). For glued-laminated members and structural composite lumber (SCL) members, the equivalent net finished width and depths corresponding to the minimum nominal width and depths of solid sawn lumber are required as specified in Table 602.4. Cross-laminated timber (CLT) dimensions used in this section are actual dimensions.
- 602.5 Type V.
- - Type V construction is that type of construction in which the structural elements, exterior walls and interior walls are of any materials permitted by this code.

There is not enough specific information given to make that determination - other that it is not Type I, Type II, or Type IV.

That leaves either Type III or Type V. I suspect the type of construction will be Type V due to the ICF construction.

Have the design professional of record specify what they state the Type of Construction is for their design, or provide as much information as the building department needs to make that determination.

How are you getting by with only 15/32 (basically 1/2") roof decking? I would have expected to see 19/32 minimum.

Be sure to select a metal roofing type which will stand up to the environment you will be placing it in. Another thing to consider is installing a single-ply modified bitumen roof covering as the 'underlayment', then a slip sheet (if needed) and the metal roofing over that - when the metal roofing is damaged or blows off during a high wind event (hurricane), you still have a "roof covering" on the structure and any resulting water intrusion damage will be less. That "roof covering" would not require replacing when replacing the damaged or missing metal roof panels - the extra cost of the single-ply roof covering would most likely be offset at the first high wind event by the reduction of interior damage.

Be careful of making the building "too tight", as that requires fresh air ventilation to be provided. While you can "get away with" meeting the FBC requirements, which have been tampered with by non-building legislators (who should keep their noses out of the FBC, but continually stick their noses into the fBC on behalf of special interest contractor, to the detriment of the building and buying public) - I recommend following the IBC guidelines (which exceed the FBC weaker guidelines for ventilation and fire (i.e.., the Florida legislators stuck their noses into the code on behalf of their special interest contractors and prohibited the FBC from requiring fire sprinklers, from requiring door closers on garage to dwelling unit doors, and many other code aspects).

If you want a "better" house, meet the most stringent of the the IBC and FBC requirements, that is permitted as it is permitted "to exceed" the "minimum requirements" of the FBC.