I am building a small retaining wall (2 feet tall) and have 2 questions. 1)Can I use large basic concrete block on the base (buried) course and my stackable finished concrete blocks on the second course? The 1st course will not be seen. They are cheaper and the concrete block is more substantial than the stackable stuff. 2) I want to put a shed in front of my wall and will be using sonotubes for the footings. What distance from the front of the wall would you suggest drilling for the tubes? I want to be able to walk into the shed without a large gap between the shed and wall.
Most decent retaining wall blocks have some shear key to prevent sliding. You could have the entire layers of the retaining wall block eventually slide off the common block with a smooth top. Also, common block can settle easier because they do not have a solid bottom.