Page 149 - 2018_IRC

FOUNDATIONS

within the applicability limits of Section R608.2 shall be 2. Stem walls laterally supported at top. Concrete
designed and constructed in accordance with the provi- stem walls that are monolithic with slabs-on-
sions of this section, ACI 318, ACI 332 or PCA 100. Con- ground or are otherwise laterally supported by
crete foundation walls that support above-grade concrete slabs-on-ground shall be vertically reinforced
walls that are not within the applicability limits of Section in accordance with Section R608.6 and Table
R608.2 shall be designed and constructed in accordance R608.6(1), R608.6(2) or R608.6(3) for above-
with the provisions of ACI 318, ACI 332 or PCA 100. grade walls. Where the unbalanced backfill
Where ACI 318, ACI 332, PCA 100 or the provisions of retained by the stem wall is greater than 18
this section are used to design concrete foundation walls, inches (457 mm), the connection between the
project drawings, typical details and specifications are not stem wall and the slab-on-ground, and the por-
required to bear the seal of the architect or engineer tion of the slab-on-ground providing lateral
responsible for design, unless otherwise required by the support for the wall shall be designed in accor-
state law of the jurisdiction having authority. dance with PCA 100 or with accepted engineer-
ing practice. Where the unbalanced backfill
R404.1.3.1 Concrete cross section. Concrete walls retained by the stem wall is greater than 18
constructed in accordance with this code shall comply inches (457 mm), the minimum nominal thick-
with the shapes and minimum concrete cross-sectional ness of the wall shall be 6 inches (152 mm).
dimensions required by Table R608.3. Other types of
forming systems resulting in concrete walls not in com- R404.1.3.2.2 Concrete foundation stem walls sup-
pliance with this section and Table R608.3 shall be porting light-frame above-grade walls. Concrete
designed in accordance with ACI 318. foundation stem walls that support light-frame
above-grade walls shall be designed and constructed
R404.1.3.2 Reinforcement for foundation walls. in accordance with this section.
Concrete foundation walls shall be laterally supported
at the top and bottom. Horizontal reinforcement shall 1. Stem walls not laterally supported at top. Con-
be provided in accordance with Table R404.1.2(1). crete stem walls that are not monolithic with
Vertical reinforcement shall be provided in accordance slabs-on-ground or are not otherwise laterally
with Table R404.1.2(2), R404.1.2(3), R404.1.2(4), supported by slabs-on-ground and retain 48
R404.1.2(5), R404.1.2(6), R404.1.2(7) or R404.1.2(8). inches (1219 mm) or less of unbalanced fill,
Vertical reinforcement for flat basement walls retaining measured from the top of the wall, shall be con-
4 feet (1219 mm) or more of unbalanced backfill is per- structed in accordance with Section R404.1.3.
mitted to be determined in accordance with Table Foundation stem walls that retain more than 48
R404.1.2(9). For basement walls supporting above- inches (1219 mm) of unbalanced fill, measured
grade concrete walls, vertical reinforcement shall be the from the top of the wall, shall be designed in
greater of that required by Tables R404.1.2(2) through accordance with Sections R404.1.4 and
R404.1.2(8) or by Section R608.6 for the above-grade R404.4.
wall. In buildings assigned to Seismic Design Category 2. Stem walls laterally supported at top. Concrete
D , D or D , concrete foundation walls shall also com- stem walls that are monolithic with slabs-on-
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ply with Section R404.1.4.2. ground or are otherwise laterally supported by
R404.1.3.2.1 Concrete foundation stem walls sup- slabs-on-ground shall be constructed in accor-
porting above-grade concrete walls. Foundation dance with Section R404.1.3. Where the
stem walls that support above-grade concrete walls unbalanced backfill retained by the stem wall
shall be designed and constructed in accordance is greater than 48 inches (1219 mm), the con-
with this section. nection between the stem wall and the slab-
on-ground, and the portion of the slab-on-
1. Stem walls not laterally supported at top. Con- ground providing lateral support for the wall,
crete stem walls that are not monolithic with shall be designed in accordance with PCA 100
slabs-on-ground or are not otherwise laterally or in accordance with accepted engineering
supported by slabs-on-ground shall comply practice.
with this section. Where unbalanced backfill R404.1.3.3 Concrete, materials for concrete, and
retained by the stem wall is less than or equal to forms. Materials used in concrete, the concrete itself
18 inches (457 mm), the stem wall and above- and forms shall conform to requirements of this section
grade wall it supports shall be provided with or ACI 318.
vertical reinforcement in accordance with Sec-
tion R608.6 and Table R608.6(1), R608.6(2) or R404.1.3.3.1 Compressive strength. The minimum
R608.6(3) for above-grade walls. Where unbal- specified compressive strength of concrete, f ′ , shall
c
anced backfill retained by the stem wall is comply with Section R402.2 and shall be not less
greater than 18 inches (457 mm), the stem wall than 2,500 psi (17.2 MPa) at 28 days in buildings
and above-grade wall it supports shall be pro- assigned to Seismic Design Category A, B or C and
vided with vertical reinforcement in accordance 3000 psi (20.5 MPa) in buildings assigned to Seis-
with Section R608.6 and Table R608.6(4). mic Design Category D , D or D .
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124 2018 INTERNATIONAL RESIDENTIAL CODE ®
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