Question
I am about to start building a retaining wall around a flower bed right off of the back of my back patio (slab). The problem is, right off the patio the yard starts to slope down. I want to build the wall to wrap around the flower bed (length of patio) and meet the back corners of thr patio slab. At the corners I will only need one stone to get my height but at the lowest part of the wall I will need 4-5 stones. My question is, how do I dig my trench in order to keep the entire wall level? At the corners of the patio do I need to dig much lower or should I "step" the stones and just bury the lower portion to hide the stepping? I hope this makes sense, its difficult to explain without showing the area. Thank you for any help.  

Answer
I understand completely, this is typical for most walls where there s any change in grade. However, this is a complicated project for a "do-it yourselfer" and is often why so many homeowner built walls end up looking off-level or falling over. Here is what you will need to do. In simple terms you won't step the wall, instead, you will "step the footing". You will dig your trench and "step it" where needed to account for the additional block height. Each step should be approximately equal to the height of one block. Dig about 4-6" deeper than you need to dig just for the blocks so you can put in 4-6"minimum of gravel as a footer. Then tamp that gravel with a tamper or small vibratory plate compactor till it is level and well compacted. Install your first course of blocks across the gravel till it hits the "step" in the footing trench. Use a minimum 48" long level to be sure the blocks are level. Tamp them lightly into place. Continue to do this for each course. Check that the second course of block will transition correctly from on top of the first course onto the adjacent gravel of the stepped footing. If not, adjust the depth of the step and gravel accordingly so the second course remains level with no change in the top of the course. Do this at each step in the footing. If you do all this correctly the top course will come out level. It is best to do this with a tripod and a sight level and rod to be super accurate. (this tool not for do-it-yourself).
Also I generally recommend large blocks 50-80lbs range for permanent walls. The small blocks sold in most home stores are not substantial enough to remain solid and level.
Best of Luck,
Sean J Murphy
www.amenityarchitects.com