Diy Concrete Bag Retaining Wall . Create a flat area at least 4 to 6 in. An easy way to build retaining walls leave the concrete in bag stack like legos wet with a hose core77. OwnerBuilderBook com Miscellaneous Forum Concrete bag Retaining wall from www.pinterest.co.uk All these dimensions and mass allow the wall to be built and hold up against the. To make concrete, you typically have to mix cement with water and aggregates, put it into a mold, and. An easy way to build retaining walls leave the concrete in bag stack like legos wet with a hose core77.