Foundation adjacent to slope

[HokieNation]

I like to get an opinion on shallow foundation on top of hill or adjacent to slope (on high side). This is an addition of three story sunroom to existing house where foundation will be at high side of slope. Per IBC Figure 1808.7.1 if the distance between edge of slope and face of footing is H/3 (H = difference in height from top of slope to bottom of slope) or 40 ft whichever is smaller it is okay to locate footing adjacent to slope as long as this criteria is met.

Now if the height difference is 10 ft with uniform slope by lowering footing down 4 ft by keeping face of footing at high point of slope it will keep face of footing H/3 away from slope.

I was wondering if code prescribes this and is okay move forward by relying on that diagram?

Thanks all in advance for input.

 

[FixedEarth]

Navy Design Manual DM 7.2, p 135-136 (available online) has more detailed approach on determining the ultimate bearing capacity. You also need to check settlement of the footing, if slope creep force is applicable and if you may get a lateral fill extension. You can avoid all this by using drilled pier support for foundations within 15 ft of a dscending slope.

For example, if the upper 6 ft soils are prone to slope creep, then yes you meet the H/3 Code requirement but will likely get distress within several years. Check with your soils firm.

http://www.soilstructure.com/