2 meter high retaining wall

[ryanstev]

I'm on a cross leased section, between the house up top and my own is a bank, where my section was cut in 1991, leveled and my house built.
It's never been retained, it has a couple of concrete slabs leaning against it, not doing much, they're only a meter tall too, but it seems pretty stable.

On one end of the bank it slopes down, I'd like to dig into the bank to remove this slope on the corner of my section, which will require a retaining wall, about a meter tall to be built, no problem.
The issue is the other end of the bank, which I don't need to dig into is around 2 meters high, it'd look silly having half a retaining wall along a bank, so I'm not sure what to do here.


I live in Auckland, so can build a 1.5 meter high wall, without consent, I was talking to someone and he suggested I build a 1 meter high wall, dig 500mm further into the bank, then build another 1 meter high wall at that end.


I haven't been able to find any information about this, apart from a page talking about surcharges, it said if the ground was clay (which mine is) I need a 27 degree angle from the base of the wall.


I can actually build a one meter wall, dig in 1.5 meters, (so around a 27 degree angle from the base of the wall) then build another wall, so on paper it seems like it would be legal for me to do this, but I'd appreciate any feedback.


Followup question - Is it strange at all that the bank has never been retained?
It has growth on it now, but originally it would have been a bare clay bank, how did that pass the initial inspection?


Here's a picture of the wall, as best I really can.
This is the 2 meter high end, it's about a meter from my house, covered in ferns and what-not, those concrete slabs are the only ones along that bank, they can't be doing much.

[John the builder]

a batter is acceptable the issue is when the cut is threatening the nieghbour or other property.

where is the boundary?

district plan can stop excavations without RC and near boundary?

2 1000m walls will likely cost more than a 2.0m one with consent?

[ryanstev]

To retain this I have two choices, that bank is approximately 13 meters long.
Option one is to make a single retaining wall at 1 meter height for around 10 meters in length, then make the last 3 meters length a height of 2 meters, I'd then need a consent.
Option two is to make a retaining wall at 1 meter height for the full length, then at the last 3 meters dig into the bank and make another 1 meter high bank, I wouldn't need a consent.

In the picture I attached you can see the house, that's the master bedroom window box, if I did option 2 I'd have a much bigger view, I'd have flowers, etc, on the top of the first retaining wall, so can make it look quite nice, it'll give the impression of more space, especially when you walk around that side of the house, as the retaining wall will be at hip height.

The boundary is approximately 1.8 meters from the bank, so I'll basically be building the top retaining wall right on the boundary.

[John the builder]

or build a 1-1.5 retaining wall and then batter the last bit to the boundary? (flatten off top further back to avoid surcharge issue)

[ryanstev]

This sounds easier, but I haven't found much information on this.

I've got just enough space to build a 1 meter wall where the bank is, dig in 1.5 meters, then build another 1 meter wall, which will be right on the boundary.

Are you saying I could build the first 1 meter wall, then batter all the way to the top? Wouldn't I need to batter further back from the first wall? At a 27 degree angle, roughly 1.5 meters from the base of the wall? If so, that's basically the boundary, I couldn't batter from there.

I've made a simple cross section of the bank:



The red line is the current bank, two meters high (it's not straight up, but good enough)
You can see the first black retaining wall (it'll be leaning back 1:10) a meter high, then it's flat for 1.5 meters, then there's another 1 meter wall.
The blue line is the boundary, there's no room for anything else there.

Maybe I should just pay for a building consent and have a 2 meter retaining wall built on the boundary and be done with it.

[John the builder]

find out if there are planning issues with a discrete enquirey to the council.
If your wall has stood the rtest of time with no retaining then the batter could be a lot steeper (ask an engineer?)

[ryanstev]

I called them a bit earlier, I've just received building consent for work under my house and the existing plans showed a timber retaining wall along there.
I asked them if consent had been granted for a retaining wall, they said it was applied for back in 1992 (the house was built in 1991) but withdrawn.

Since the wall is on the plans, if I had the ability, I'd just build the 2 meter wall where the plans say it is, but I can't bore a 2 meter deep post hole, so that's out.

[ryanstev]

I've had one idea, since I only need to dig into the bank at one end and only a little bit, maybe I could build the 1 meter retaining wall where I actually need it and build a fake retaining wall over the 2 meter high section, basically just a facade for aesthetics.
Since I wouldn't be digging into the 2 meter high part of the bank, then this should be alright.