Page 126 - 2018_IRC

FOUNDATIONS

R403.1.7.4 Alternate setbacks and clearances. Alter- shallow foundations shall be protected from frost in accor-
nate setbacks and clearances are permitted, subject to dance with Section R403.1.4.
the approval of the building official. The building offi- R403.3.1.1 Attachment to unheated slab-on-ground
cial is permitted to require an investigation and recom- structure. Vertical wall insulation and horizontal insu-
mendation of a qualified engineer to demonstrate that lation of frost-protected shallow foundations that adjoin
the intent of this section has been satisfied. Such an a slab-on-ground foundation that does not have a
investigation shall include consideration of material, monthly mean temperature maintained at not less than
height of slope, slope gradient, load intensity and ero- 64°F (18°C) shall be in accordance with Figure
sion characteristics of slope material.
R403.3(3) and Table R403.3(1). Vertical wall insulation
R403.1.8 Foundations on expansive soils. Foundation shall extend between the frost-protected shallow foun-
and floor slabs for buildings located on expansive soils dation and the adjoining slab foundation. Required hor-
shall be designed in accordance with Section 1808.6 of the izontal insulation shall be continuous under the
International Building Code. adjoining slab foundation and through any foundation
Exception: Slab-on-ground and other foundation sys- walls adjoining the frost- protected shallow foundation.
tems that have performed adequately in soil conditions Where insulation passes through a foundation wall, it
similar to those encountered at the building site are per- shall be either of a type complying with this section and
mitted subject to the approval of the building official. having bearing capacity equal to or greater than the
structural loads imposed by the building, or the building
R403.1.8.1 Expansive soils classifications. Soils shall be designed and constructed using beams, lintels,
meeting all of the following provisions shall be consid- cantilevers or other means of transferring building loads
ered to be expansive, except that tests to show compli- such that the structural loads of the building do not bear
ance with Items 1, 2 and 3 shall not be required if the on the insulation.
test prescribed in Item 4 is conducted:
R403.3.1.2 Attachment to heated structure. Where a
1. Plasticity Index (PI) of 15 or greater, determined frost-protected shallow foundation abuts a structure that
in accordance with ASTM D4318. has a monthly mean temperature maintained at not less
2. More than 10 percent of the soil particles pass a than 64°F (18°C), horizontal insulation and vertical wall
No. 200 sieve (75 µm), determined in accordancem), determined in accordance insulation shall not be required between the frost-pro-
with ASTM D422. tected shallow foundation and the adjoining structure.
Where the frost-protected shallow foundation abuts the
3. More than 10 percent of the soil particles are less heated structure, the horizontal insulation and vertical
than 5 micrometers in size, determined in accor- wall insulation shall extend along the adjoining founda-
dance with ASTM D422. tion in accordance with Figure R403.3(4) a distance of
4. Expansion Index greater than 20, determined in not less than Dimension A in Table R403.3(1).
accordance with ASTM D4829. Exception: Where the frost-protected shallow foun-
R403.2 Footings for wood foundations. Footings for wood dation abuts the heated structure to form an inside
foundations shall be in accordance with Figures R403.1(2) corner, vertical insulation extending along the
and R403.1(3). Gravel shall be washed and well graded. The adjoining foundation is not required.
maximum size stone shall not exceed / inch (19.1 mm). R403.3.2 Protection of horizontal insulation below
3
4
Gravel shall be free from organic, clayey or silty soils. Sand ground. Horizontal insulation placed less than 12 inches
shall be coarse, not smaller than / -inch (1.6 mm) grains and (305 mm) below the ground surface or that portion of hor-
1
16
shall be free from organic, clayey or silty soils. Crushed stone izontal insulation extending outward more than 24 inches
shall have a maximum size of / inch (12.7 mm). (610 mm) from the foundation edge shall be protected
1
2
R403.3 Frost-protected shallow foundations. For buildings against damage by use of a concrete slab or asphalt paving
where the monthly mean temperature of the building is main- on the ground surface directly above the insulation or by
tained at not less than 64°F (18°C), footings are not required cementitious board, plywood rated for below-ground use,
to extend below the frost line where protected from frost by or other approved materials placed below ground, directly
insulation in accordance with Figure R403.3(1) and Table above the top surface of the insulation.
R403.3(1). Foundations protected from frost in accordance R403.3.3 Drainage. Final grade shall be sloped in accor-
with Figure R403.3(1) and Table R403.3(1) shall not be used dance with Section R401.3. In other than Group I Soils, as
for unheated spaces such as porches, utility rooms, garages detailed in Table R405.1, gravel or crushed stone beneath
and carports, and shall not be attached to basements or crawl horizontal insulation below ground shall drain to daylight
spaces that are not maintained at a minimum monthly mean or into an approved sewer system.
temperature of 64°F (18°C).
R403.3.4 Termite protection. The use of foam plastic in
Materials used below grade for the purpose of insulating areas of “very heavy” termite infestation probability shall
footings against frost shall be labeled as complying with be in accordance with Section R318.4.
ASTM C578. R403.4 Footings for precast concrete foundations. Foot-
R403.3.1 Foundations adjoining frost-protected shal- ings for precast concrete foundations shall comply with Sec-
low foundations. Foundations that adjoin frost-protected tion R403.4.

2018 INTERNATIONAL RESIDENTIAL CODE ® 101
Copyrighted © 2017 by, or licensed to, ICC (ALL RIGHTS RESERVED); licensed to UL, LLC pursuant to License Agreement with ICC. No further reproductions authorized or distribution authorized.
ANY UNAUTHROIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT; AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.