Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 18 - Soils and Foundations › Section 1808 - FOUNDATIONS › Subsection 1808.7 - Foundations on or adjacent to slopes

Current through Register 1525, July 5, 2024
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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				  image
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.