Is there a soil capacity that can be assumed or do you have to do an actual test?


The IRC allows for 1500 psf to be used unless local conditions are known otherwise.


This FAQ is based on the presentation of BCD303 – Design for Code Acceptance No. 6 - Prescriptive Residential Deck Construction Guide.

Also, see Page 12 of Part II: Design Values for Structural Members for background on the Wet Service Factor.