Walls should be constructed to resist vandalism and facilitate ease of maintenance. Exterior and interior walls within inmate housing and activity areas shall be constructed as follows:     
       (1) Exterior walls:                (A) a minimum 8" concrete block vertically reinforced by #3 bars 8" on center and all cells filled with 2500 psi grout, or                 (B) a minimum of 4" thick concrete plank reinforced with #4 bars 8" on center each way, or                 (C) a minimum 3/16" thick steel plate.        
       (2) Interior walls:                (A) a minimum 6" concrete block vertically reinforced by #3 bars 8" on center and all cells filled with 2500 psi grout, or                 (B) a minimum 4" thick concrete plank reinforced with #4 bars 8" on center each way, or                 (C) a minimum 3/16" thick steel plate. Innovative design concepts are encouraged and comparable materials and methods approved by the Commission may be utilized for exterior and interior wall construction.        
     Source Note:        The provisions of this §259.240 adopted to be effective December 12, 1994, 19 TexReg 9376; amended to be effective February 4, 1999, 24 TexReg 591