Footings

Hi, This will have a number of factors including ground type, amount of ground being retained and whether or not you have reinforcements or drainage behind the proposed wall.

I Probably 600mm deep 300mm wide. Also I'd recommend using concrete blocks and not breeze blocks. For a retaining wall your better off laying the blocks flat or (belly down) so the wall is 215mm instead of 100mm will be much stronger. But you will use twice as many blocks.

750mm x 450mm concrete mass fill. Solid concrete blocks to form footings laid flat.

The death of the wall will be defined by the type of ground you find always finds hard ground. I always make sure I am 675mm deep allow 225mm concrete and 450mm or 600mm wide . Do not try and cut corners to avoid future problems.

300mm depth by 500mm wide so your wall has 150mm concrete either side of the wall when centred on the concrete.