Allan Block walls should always include a wall rock column behind the block, which is typically 12 in. (30 m) in depth. Section 1 Part 2.2 in the covers what type of rock is acceptable. For curved and cornered walls, additional depth of wall rock should be specified to promote greater stability in these areas. Additional depth of wall rock is dependent on the total height of the wall. At the top of the wall, above the wall rock column it is also common to place a horizontal layer of landscape fabric to protect the wall rock from being infiltrated by the topsoil placed to finish the wall. (ref. BP, Chapter 6.4)Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry. To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.