The importance of a 2’-0” topographical survey:
When building on a sloping site, it is recommended to get a “topo” around the building location in 2’-0” elevation increments. Your designer will use this detail to determine the ideal walkout basement height and the porch support pier details. This information will also dictate lengths and heights of retaining walls required.
Some counties here in East Tennessee require “engineered” retaining wall designs when the slope exceeds 30% in steepness. 30% is the same as 16.7 degrees, or equal to a 3.6 to 12 roof pitch. During the devastating wildfires in 2016, railroad tie type of retaining walls burned up and the subsequent winter rains caused serious runoff erosion. Since then, combustible retaining wall designs on slopes greater than 30% have been prohibited.