Civil Engineering Reference
In-Depth Information
TABLE 14.5
Excavation, Grading, and Fill
Topic
Discussion
Excavation
and grading
For excavation and grading, the
International Building Code
(2012) states:
“Section 1804.1 Excavation near foundations. Excavation for any purpose shall
not remove lateral support from any foundation without first underpinning or
protecting the foundation against settlement or lateral translation.
Section 1804.2 Placement of backfill. The excavation outside the foundation
shall be backfilled with soil that is free of organic material, construction debris,
cobbles and boulders or with a controlled low-strength material (CLSM). The
backfill shall be placed in lifts and compacted in a manner that does not damage
the foundation or the waterproofing or dampproofing material. Exception: CLSM
need not be compacted.
Section 1804.3 Site grading. The ground immediately adjacent to the founda-
tion shall be sloped away from the building at a slope of not less than one unit
vertical in 20 units horizontal (5-percent slope) for a minimum distance of 10 feet
(3048 mm) measured perpendicular to the face of the wall. If physical obstruc-
tions or lot lines prohibit 10 feet (3048 mm) of horizontal distance, a 5-percent
slope shall be provided to an approved alternative method of diverting water away
from the foundation. Swales used for this purpose shall be sloped a minimum of
2 percent where located within 10 feet (3048 mm) of the building foundation.
Impervious surfaces within 10 feet (3048 mm) of the building foundation shall
be sloped a minimum of 2 percent away from the building. Exception: Where
climatic or soil conditions warrant, the slope of the ground away from the build-
ing foundation shall be permitted to be reduced to not less than one unit vertical
in 48 units horizontal (2-percent slope). The procedure used to establish the final
ground level adjacent to the foundation shall account for additional settlement of
the backfill.”
This section of the code also provides a regulation that restricts grading that
will result in an increase in flood levels during the occurrence of the design flood
(Section 1804.4).
The geotechnical engineer will often provide much more extensive grading
specifications then those listed above.
For compacted fill material, the
International Building Code
(2012) states:
Compacted
fill
“Section 1804.5 Compacted fill material. Where shallow foundations will
bear on compacted fill material, the compacted fill shall comply with the
provisions of an approved geotechnical report, as set forth in Section 1803.
Exception: Compacted fill material 12 inches (305 mm) in depth or less need
not comply with an approved report, provided the in-place dry density is not
less than 90 percent of the maximum dry density at optimum moisture content
in accordance with ASTM D 1557. The compaction shall be verified by special
inspection in accordance with Section 1705.6.”
