Hi there. I am planning a low retaining wall 4.5m x 0.5m high in my terraced house's garden. It will incorporate a step down from a planting area to a dining site. I am proposing a curved facing wall (4.5m) of yorkstone walling bricks on the lower side and backed with a separate straight wall (4.3m) of breeze blocks and rubble/gravel on the higher side to take the weight of the retained soil. I have dug a single trench, which to allow for the curve is around 1 m wide. The earth is relatively soft, non clay but I have now hit hard ground 30 cms down. There are no trees or houses within 5m of the site. Any comments/assistance on the following points?
1. hardcore base to the foundation - how deep does this need to be? I was thinking 50mm but am not sure this will be enough.
2. how deep should the concrete be? I have seen 150m mentioned eleswhere but this seems excessive for what I want.
3. Given the depth and width the trench, can I lay the a couple of courses of breeze blocks on their side (underground) on top of the concrete before laying the bricks/blocks in the usual way?
Thanks for your advice.