Retaining walls can be built in many levels. For every wall that is built a new footing as to be prepared and at list one raw of blocks has to be berried. The fist wall needs to be built with drainage gravel and pipe behind with geogrid installed at list every 24 inches. Or every 3 rows. The soil used to back fill the wall has to be compacted in layers to achieve at list 90 % density compaction. The second walls must be built far back enough to let it sit on verging ground and the same drainage and compaction procedure has to be fallowed for the second and third wall. The block selection and proper weight and size is very important and it as to be based on the height and size of the retaining wall. Not every block is suitable for any wall height. Gappsi also glues most of the walls that we build even when the wall manufacture does not recommends to do so. for farther information please contact the long island retaining wall installer company or call 631 543-1177 or visit our web site at www.gappsi.com