Page 79 - 2018_IRC

BUILDING PLANNING

TABLE R301.2.2.1.1 4. Five pounds per square foot (240 Pa) for interior
SEISMIC DESIGN CATEGORY DETERMINATION
light-frame cold-formed steel walls.
SEISMIC DESIGN CATEGORY
5. Eighty pounds per square foot (3830 Pa) for 8-
CALCULATED S DS
S ≤ 0.17g A inch-thick (203 mm) masonry walls.
DS
0.17g < S ≤ 0.33 B 6. Eighty-five pounds per square foot (4070 Pa) for

DS
0.33g < S ≤ 0.50 C 6-inch-thick (152 mm) concrete walls.

DS
0.50g < S ≤ 0.67g D 0 7. Ten pounds per square foot (480 Pa) for SIP
DS
0.67g < S ≤ 0.83g D 1 walls.
DS
0.83g < S ≤ 1.25g D 2 Exceptions:
DS
1.25g < S DS E 1. Roof and ceiling dead loads not exceeding 25
pounds per square foot (1190 Pa) shall be per-
R301.2.2.1.2 Alternative determination of Seis- mitted provided that the wall bracing amounts
mic Design Category E. Buildings located in Seis- in Section R602.10.3 are increased in accor-
mic Design Category E in accordance with Figure dance with Table R602.10.3(4).
R301.2(2), or Figure R301.2(3) where applicable, 2. Light-frame walls with stone or masonry
are permitted to be reclassified as being in Seismic veneer shall be permitted in accordance with
Design Category D provided that one of the follow- the provisions of Sections R702.1 and R703.
2
ing is done:
3. Fireplaces and chimneys shall be permitted in
1. A more detailed evaluation of the seismic accordance with Chapter 10.
design category is made in accordance with
the provisions and maps of the International R301.2.2.3 Stone and masonry veneer. Anchored
Building Code. Buildings located in Seismic stone and masonry veneer shall comply with the
Design Category E in accordance with Table requirements of Sections R702.1 and R703.
R301.2.2.1.1, but located in Seismic Design R301.2.2.4 Masonry construction. Masonry construc-
Category D in accordance with the Interna- tion in Seismic Design Categories D and D shall com-
0
1
tional Building Code, shall be permitted to be ply with the requirements of Section R606.12.1.
designed using the Seismic Design Category Masonry construction in Seismic Design Category D
D requirements of this code. shall comply with the requirements of Section 2
2
2. Buildings located in Seismic Design Category R606.12.4.
E that conform to the following additional R301.2.2.5 Concrete construction. Buildings with
restrictions are permitted to be constructed in exterior above-grade concrete walls shall comply with
accordance with the provisions for Seismic PCA 100 or shall be designed in accordance with ACI
Design Category D of this code: 318.
2
2.1. All exterior shear wall lines or braced Exception: Detached one- and two-family dwell-
wall panels are in one plane vertically ings in Seismic Design Category C with exterior
from the foundation to the uppermost above-grade concrete walls are allowed to comply
story.
with the requirements of Section R608.
2.2. Floors shall not cantilever past the R301.2.2.6 Irregular buildings. The seismic provi-
exterior walls.
sions of this code shall not be used for structures, or
2.3. The building is within the requirements portions thereof, located in Seismic Design Categories
of Section R301.2.2.2.6 for being con- C, D , D and D and considered to be irregular in
0
1
2
sidered as regular. accordance with this section. A building or portion of a

R301.2.2.2 Weights of materials. Average dead loads building shall be considered to be irregular where one
shall not exceed 15 pounds per square foot (720 Pa) for or more of the conditions defined in Items 1 through 7
the combined roof and ceiling assemblies (on a hori- occur. Irregular structures, or irregular portions of
zontal projection) or 10 pounds per square foot (480 structures, shall be designed in accordance with
Pa) for floor assemblies, except as further limited by accepted engineering practice to the extent the irregular
Section R301.2.2. Dead loads for walls above grade features affect the performance of the remaining struc-
shall not exceed: tural system. Where the forces associated with the
irregularity are resisted by a structural system designed
1. Fifteen pounds per square foot (720 Pa) for exte- in accordance with accepted engineering practice, the
rior light-frame wood walls. remainder of the building shall be permitted to be
2. Fourteen pounds per square foot (670 Pa) for designed using the provisions of this code.
exterior light-frame cold-formed steel walls. 1. Shear wall or braced wall offsets out of plane.
3. Ten pounds per square foot (480 Pa) for interior Conditions where exterior shear wall lines or
light-frame wood walls. braced wall panels are not in one plane vertically

54 2018 INTERNATIONAL RESIDENTIAL CODE ®
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