In all the images you can see that the soil and debris had built up to the bottom horizontal timber of the fence line, so a good 30-40cm was stacked up against the fence. The top images show the area towards the back Banksia and we move down towards the house to where the Callistamon is - I'll show a view from above next so you can see that there was a concrete retaining wall built (probably to lay the house slab down) sloping away from the house that starts just about where the Callistamon is and runs the full length of the house down to the front.
That's the same Callistamon (as the image above this one, only looking down from the balcony) - see the retaining wall that slopes down towards the fence...this is one of the reasons I decided to do the retaining wall because this void was useless space that only collected debris...and by filling it in I not only leveled the block but I gained an extra metre or more of width to the block.
The above 11 images show the process of the retaining wall (at the back only) once I had cleared along the fence line. The posts had to go in then the horizontal timbers, I then sheeted in sturdy black plastic to reduce contact with moisture, I laid ag-pipe down the length of it, covered that with gravel (remember all the gravel I dug up from my first garden bed...yes, it came in very handy) and other building waste for drainage, covered that with sand and then soil - which is sandy soil anyway, but I did mix in some good organic soil as I was going to create a garden bed here now.
The retaining wall runs pretty much the length of the property on that right-hand boundary and so now I'll show pictures of it from the front of the house.
The top image shows the view looking down towards the front right-hand side of the house (from the back balcony) and shows that original concrete retaining wall running the length of the house with the new retaining wall finished, lined and ready to be filled in...the images that follow on from that show that same process as the back where it ag-pip was laid down, gravel on top, sand and then soil.
This is now a super long post and I will show the finished result in the next one...
So, the mistake I made in regards to the retaining wall in general was not seeking advice before doing it, especially from an engineer, I just assumed it was a good thing to do and couldn't possibly have any ill-effects. Overall it has been good but I should have consulted an engineer to seek professional advice. Only recently I saw a crack in the floor slab in my garage and then found minor cracks in the bricks on the front right-hand corner of my house, the garage is at the front on the right-hand side and so it was this wall (in the last 7 images the image 2nd from the top shows that corner of the house). Of course I kind of freaked out thinking that corner of the house had shifted and it would need underpinning and all the rest and so I called an engineer. Thankfully he believes the shift is all within tolerance and nothing too severe, definitely not needing underpinning, all houses shift to some degree. The major cause is that one downpipe runs down that front corner and is not draining properly so I also have to have that piping ripped up and replaced. NB: This property is about 40 years old now and those pipes would be the original terracotta ones, so I just need to switch them over to the pvc ones and no more problems.
I showed the engineer pictures of what was underneath the soil and mulch (i.e. that concrete retaining wall that slopes down from the house - as it runs the length of the house) he said that by building the retaining wall what probably happened was the weight of the house no longer relied solely on the original retaining wall as the new retaining wall was also taking some of the weight and so it probably didn't help any when that front corner was being soaked with rain water that couldn't drain away...but it didn't cause the problem...the bad drainage did, he just said it probably didn't help...and so folks, if you want to do something like this yourself I would strongly advise on seeking a professional opinion first.
Another thing that was that it probably didn't do anything to help both Banksia's, as they were sitting right along the fence line where the land sloped away. Don't get me wrong, I wasn't completely without common sense and did ensure that I didn't build up the soil and mulch around the trunks, I left really deep, wide wells to keep the land level to what they were accustomed to, however, I'm sure it did change their conditions slightly and would have only assisted in their decline, though as with all things they too have a life-span and were basically reaching the end of theirs.
I would have also liked to have done it properly so it didn't butt up against the existing fence and would have preferred to have incorporated a new fence on top but the owner's of next door were selling and not really fussed to get involved and so I just did what I did.