Reinforced grouted masonry block walls (8 x 8 x 16) can go over 20'. They should be designed by an engineer and built by people who know what they are doing.
From the 2003 International Residential Code: 311.5.6 Handrails. Handrails shall be provided on at least one side of each continuous run of treads or flight with four or more risers. - Maximum riser...