1808.7 - Foundations on or adjacent to slopes
The placement of buildings and structures on or adjacent to slopes steeper than one unit vertical in three units horizontal (33.3-percent slope) shall comply with Sections 1808.7.1 through 1808.7.5.
1808.7.1
Building clearance from
ascending slopes. In general, buildings below slopes shall be set a
sufficient distance from the slope to provide protection from slope drainage,
erosion and shallow failures. Except as provided in Section 1808.7.5 and Figure
1808.7.1, the following criteria will be assumed to provide this protection.
Where the existing slope is steeper than one unit vertical in one unit
horizontal (100-percent slope), the toe of the slope shall be assumed to be at
the intersection of a horizontal plane drawn from the top of the foundation and
a plane drawn tangent to the slope at an angle of 45 degrees (0.79 rad) to the
horizontal. Where a retaining wall is constructed at the toe of the slope, the
height of the slope shall be measured from the top of the wall to the top of
the slope.
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For SI: 1 foot = 304.8 mm. |
FIGURE 1808.7.1 FOUNDATION CLEARANCES FROM SLOPES
1808.7.2
Foundation setback from descending slope surface. Foundations on
or adjacent to slope surfaces shall be founded in firm material with an
embedment and set back from the slope surface sufficient to provide vertical
and lateral support for the foundation without detrimental settlement. Except
as provided for in Section 1808.7.5 and Figure 1808.7.1, the following setback
is deemed adequate to meet the criteria. Where the slope is steeper than 1 unit
vertical in 1 unit horizontal (100-percent slope), the required setback shall
be measured from an imaginary plane 45 degrees (0.79 rad) to the horizontal,
projected upward from the toe of the slope.
1808.7.3
Pools. The setback
between pools regulated by this code and slopes shall be equal to one-half the
building footing setback distance required by this section. That portion of the
pool wall within a horizontal distance of 7 feet (2134 mm) from the top of the
slope shall be capable of supporting the water in the pool without soil
support.
1808.7.4
Foundation
elevation. On graded sites, the top of any exterior foundation shall
extend above the elevation of the street gutter at point of discharge or the
inlet of an approved drainage device a minimum of 12 inches
(305 mm) plus 2 percent. Alternate elevations are permitted subject to the
approval of the building official, provided it can be
demonstrated that required drainage to the point of discharge and away from the
structure is provided at all locations on the site.
1808.7.5
Alternate setback and
clearance. Alternate setbacks and clearances are permitted, subject to
the approval of the building official. The building
official shall be permitted to require a geotechnical investigation as
set forth in Section 1803.5.10.
Notes
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