R404.1.3 Question on Hydrostatic Pressures

[righter101]

R404.1.3 describes 2 conditions where a foundation wall design would be requried. The 2nd is when there is >48" of unbalanced backfill with no lateral support at the top or bottom.

The first condition is what my question is about. The code says design is required when "walls are subject to hydrostatic pressure from groundwater".

How do you determine when this condition exists?

My reading of various related documents, including FEMA TB1, would point me towards this being applicable when the foundation walls are below a BFE. The code however says "ground water" not "flood water".

Just curious how you all interpret this section.

Thanks.

 

[Mark K]

Code is poorly worded. If there is hydrostatic pressure irrespective whether due to ground water or flood water the wall should be designed for the forces.

 

[cboboggs]

A geo tech report would provide the classification and characteristics of the soil.