Leaning retainer walls are an expensive repair, and very dangerous for your family, costing anywhere from $450 to $600 per m² for a concrete block replacement type. This wall is leaning over 220mm and because any wall built higher than 1 metre requires engineering. The repair, to be legal and complying with the council will require certification prior to construction. When looking at a wall such as this one the total overall repair could be over $12,000 just for the rear retainer wall. Unfortunately the properties side retainer walls were also failing in a similar way and also requiring replacement.