We are having issues with a retaining wall my rear neighbour built on the boundary without our approval. They have their land backfilled hence it is an engineering wall with height from 1.8m gradual to 1m. Until we were ready to build and require to clear the land, we contacted them to remove the rocks they left behind, it was then that they told us they have been wanting to be in touch with us, to request us to share cost the engineering wall they have built. We refused after knowing our rights. Our builder advised us that we have no obligation as the retaining wall is required by the rear neighbour to keep their backfill in place. While ours, the nature state of land needs no support. They have changed their land level and we didn’t. This information totally aligns with the article I read at: Retaining Walls. As this is specific to South Australia, I’m not sure if this applys to Victoria too. If the same law applies, they should, in fact, contact us prior to building the retaining wall, providing us engineering details to assure us that our land will not be affected by the proposed retaining wall, and not to ask for cost sharing. We now require a fence to be up and issue them the "Notice Of Fence" via email. Here comes the sticky issue as the fence is to be sitting on the retaining wall. They refused us to have the fence on it and refused to share half the cost. They even shouted at the fence contractor who tried advising them. Questions: 1. Is the South Australia law in regards to Retaining Wall the same as Victoria? 2. What is the implication if the retaining wall (1.8m) built on the boundary has no council approval? 3. Are we really not obligated to share that retaining wall? 4. What if we build the fence in our land; do they have any rights to ask us to remove it later? 5. Do we have rights to ask them to move the retaining wall into their land? 6. Should we involve the neighbour whose land is at the far left end of the retaining wall? At the same time, there are so many loopholes in the “Notice To Retaining Wall” they gave us about 5 months after the retaining wall was built. Total Invoice is $10703, yet in the “Notice to Retaining Wall” given to us is $6152. If retaining wall cost is obligated to share…Why are we asked to pay more than 50%? Take a closer look at the details of the quotation. It doesn’t make sense to even split it equally: Retaining Wall, South Boundary: 17 Lineal meters 1.8m reducing to 1.0m in height Galvanised steel posts, UC 150 & UC 100, Treated pine sleepers, 100mm & 75mm Aggie Drain 100mm, Backfill with drainage scoria Cost: $7450 Retaining Wall, East Boundary: 12 Lineal meters 600m in height Galvanised steel posts, UC 100, Treated pine sleepers 75mm Aggie Drain 100mm, Backfill with drainage scoria Cost: $2280 GST: $973 TOTAL: $10703 We are on the South Boundary, why are we asked to share half the cost of the East Boundary too? Our land is 16.5m and not in straight alignment with the rear neighbour. Hence effectively the common length is probably at 14.5m. Why should we be billed the full 17m? Backfill? Bill us for the backfilling his land? Make sense? Moreover, it is a really ugly engineering retaining wall as extra posts are required as enforcement at different length interval. The rear neighbours won’t see this retaining wall, but it is in full view in our backyard. Would appreciate your help. What should we do? We prefer to work this out amicably without having to be bullied into paying unnecessarily. Them shouting at the fence contractor makes us feel really threatened; should we make a police report?