Retaining Wall Questions

[Crazy Dazz]

Ok, bit of a strange one for Ford forums, but I recall we have some stone-masons here...

Looking at a block of land to purchase...

The block is 30m deep, and overall drops away from street level. So we'd be looking to retain along the back (11m) and along the sides towards the back. That is now the normal practise here, but this is in an old part of the suburb.

Overall I would estimate that the existing block drops 1~1.5m from street to back fence so adding 1m of retaining should be plenty.

HOWEVER, the back fence is onto a commercial property (their carpark) which has already been levelled, and so it is already retained. Using that precast modular concrete ("wonderwall").

So my question is how can I "add" to the existing retaining?
Can I place "L" blocks on top of the existing retaining?

[roKWiz]

Originally Posted by Crazy Dazz

Ok, bit of a strange one for Ford forums, but I recall we have some stone-masons here...

Looking at a block of land to purchase...

The block is 30m deep, and overall drops away from street level. So we'd be looking to retain along the back (11m) and along the sides towards the back. That is now the normal practise here, but this is in an old part of the suburb.

Overall I would estimate that the existing block drops 1~1.5m from street to back fence so adding 1m of retaining should be plenty.

HOWEVER, the back fence is onto a commercial property (their carpark) which has already been levelled, and so it is already retained. Using that precast modular concrete ("wonderwall").

So my question is how can I "add" to the existing retaining?
Can I place "L" blocks on top of the existing retaining?

What are L blocks and what are you trying to achieve. 1.5mtr high is OK. Pictures ??

[naddis01]

I would assume you would need to talk to an engineer. Adding another metre on top of an existing retaining wall would surely need to be engineered correctly for the extra load.

[Citroënbender]

Absolutely. I might like to live on the edge (in a manner of speaking) but this situation is one I’d not touch without an engineer on my side.

[roKWiz]

I don't even think he is requiring a Stonemason.

Blocklayer/brickie and Casey Jones, if he's talking a 2.5mtr high wall.

[b0son]

The existing wall will have been engineered for the height it is currently at. Adding to it will be a non-starter as far as council is concerned. Simplest solution might be to set back a distance equivalent to the existing wall's height, and build your new wall there.

[arm79]

The thing I feel everyone has overlooked so far is the existing wall on the shared boundary line so that it can be used?

I doubt it would be on the shared boundary and solely on their property, so there will be zero access to adding to it, modifying or using it. Certainly not without their permission which I can't see they would give... Nor would you want to ask as you'd be responsible for any problems.

So you will end up with the kind of ridiculousness that our ****wit neighbour has bought upon us.







Everything is done on his side so he can do as he pleases without the need to involve or offer consideration to neighbours. I'd expect this would be the same.

[Crazy Dazz]

Originally Posted by roKWiz

What are L blocks and what are you trying to achieve.

L-blocks are precast reinforced concrete sections, in the shape of an 'L', where the weight of the soil on the base holds the upright in position.

I want to achieve another ~1m of retaining, in addition to the ~1m already there

[roKWiz]

Originally Posted by Crazy Dazz

L-blocks are precast reinforced concrete sections, in the shape of an 'L', where the weight of the soil on the base holds the upright in position.

I want to achieve another ~1m of retaining, in addition to the ~1m already there

So 2 mtrs high. As others have said here you need to talk to an engineer or seek advice from a company who specialize in these manufactured blocks.
(who will usually direct you to one of theirs)

If the neighbouring property is already built 1 mtr high how do you plan on finishing their side of your extra 1000mm ad on. It would then need to be freestanding above the 1000mm mark or is there an embankment above whats already done.

Other ways beside modular blocks are pre-cast concrete like arm79's pictures below or staggering 500x500x2000 stone logs, both would have to be built in front of whats there now.

With engineering approvals, I've built several retaining walls upto 2300mm high using traditional drystone methods. Obviously strength and drainage are the most critical aspects involved.

[Crazy Dazz]

Originally Posted by roKWiz

If the neighbouring property is already built 1 mtr high how do you plan on finishing their side of your extra 1000mm ad on. It would then need to be freestanding above the 1000mm mark

well yeah

that's why I'm trying to get ideas...

Currently there is ~1m of the pre-fab concrete stuff, topped by the standard 1.8m colourbond fence.
So, from what I can think of, "options" are:

1. Don't retain on the boundary. Not Ideal.
2. Put my own retaining inside coloubond fence, giving me great view into neighbouring carpark.
3. Remove colourbond, place L-blocks atop existing retaining, and replace colourbond on top. Might cause neighbours to complain to council. Might also cause existing retaining to collapse under weight.
4. Dig out existing backfill and build all new 2m retaining wall on the inside of the existing pre-fab. Remount coloubond on the new wall. This will look ugly from neighbours side, and will cause slight loss of space.
5. As above, but leave existing CB in place, and mount new fence inside. Starting to get expensive.
6. Demolish existing retaining, and rebuild from scratch. Messy and expensive. Will cause problems as will most likely require cutting the existing wall at my corners

[roKWiz]

Originally Posted by Crazy Dazz

well yeah

that's why I'm trying to get ideas...

Currently there is ~1m of the pre-fab concrete stuff, topped by the standard 1.8m colourbond fence.
So, from what I can think of, "options" are:

1. Don't retain on the boundary. Not Ideal.
2. Put my own retaining inside coloubond fence, giving me great view into neighbouring carpark.
3. Remove colourbond, place L-blocks atop existing retaining, and replace colourbond on top. Might cause neighbours to complain to council. Might also cause existing retaining to collapse under weight.
4. Dig out existing backfill and build all new 2m retaining wall on the inside of the existing pre-fab. Remount coloubond on the new wall. This will look ugly from neighbours side, and will cause slight loss of space.
5. As above, but leave existing CB in place, and mount new fence inside. Starting to get expensive.
6. Demolish existing retaining, and rebuild from scratch. Messy and expensive. Will cause problems as will most likely require cutting the existing wall at my corners

OPTION 7. Forget that block of land.

Could end up getting very expensive.

[FoxtrotGolfXray 5.0]

Originally Posted by Crazy Dazz

well yeah

that's why I'm trying to get ideas...

Currently there is ~1m of the pre-fab concrete stuff, topped by the standard 1.8m colourbond fence.
So, from what I can think of, "options" are:

1. Don't retain on the boundary. Not Ideal.
2. Put my own retaining inside coloubond fence, giving me great view into neighbouring carpark.
3. Remove colourbond, place L-blocks atop existing retaining, and replace colourbond on top. Might cause neighbours to complain to council. Might also cause existing retaining to collapse under weight.
4. Dig out existing backfill and build all new 2m retaining wall on the inside of the existing pre-fab. Remount coloubond on the new wall. This will look ugly from neighbours side, and will cause slight loss of space.
5. As above, but leave existing CB in place, and mount new fence inside. Starting to get expensive.
6. Demolish existing retaining, and rebuild from scratch. Messy and expensive. Will cause problems as will most likely require cutting the existing wall at my corners

I'm not a civil engineer, but I would think that 'options' 2 and 3 aren't really options unless you are extremely fortunate in that the existing retaining wall has been overdesigned and will allow for what is essentially a one metre extension to it.

As RW says, I don't think any of the remaining options are going to be cheap.

Time to get some professional advice (no offence to RW here, just that it's hard to know specifics when you're only going off a forum chat). It might cost you a few $$ to get that advice, but it might save you a lot more $$$ down the track.

[Crazy Dazz]

Originally Posted by roKWiz

OPTION 7. Forget that block of land.

Could end up getting very expensive.

To put this in perspective, in nearby new estates, they will commonly build limestone retaining walls up to around the 3m mark, at the rear of lots. Side boundaries typically have 2 or 3 blocks high (I'm guessing the blocks are around 30x30cm?) without any additional reinforcement.

But how expensive are we talking? It's only 11m. $10k? $20k?

[roKWiz]

Originally Posted by Crazy Dazz

To put this in perspective, in nearby new estates, they will commonly build limestone retaining walls up to around the 3m mark, at the rear of lots. Side boundaries typically have 2 or 3 blocks high (I'm guessing the blocks are around 30x30cm?) without any additional reinforcement.

But how expensive are we talking? It's only 11m. $10k? $20k?

Yeah, in estates they can build a lot of flat ground lots this way but its usually done by the building authority or developers right from the start. This only would save them a bomb of cash.

To do it individually........
Sandstone logs (on the Eastcoast) are usually 500 x 500, lengths vary to 2500mm @ around $180 each (for 2000mm ones) + delivery.
Depending on reseller. Cheaper in bulk direct from quarry.

But in this case the raw material isn't the problem, the cost of bringing in bobcat, excavator, prep work, labour and no doubt the required concrete footing that any engineer would spec.
Could easily go $50 000 + in a short time and that's if they don't find any niggle drainage issues.

I would seriously talk with people who do this kind of work (engineered approved) in your area and if agreeing to any future work have an itemised quote written up.
That's all I can offer from the otherside of Oz.

[b0son]

Originally Posted by Crazy Dazz

Side boundaries typically have 2 or 3 blocks high (I'm guessing the blocks are around 30x30cm?) without any additional reinforcement.

Don't be so sure. My neighbour has one, it collapsed in a major rain event. Easy to fix, but still..

And you haven't addressed the elephant in the room. What about if the neighbour decides to object to your DA to replace the wall? You'd likely eventually get permission, but is it a headache you want?

[Crazy Dazz]

Originally Posted by roKWiz

That's all I can offer from the otherside of Oz.

Thanks for the input, it is appreciated

[Crazy Dazz]

Originally Posted by roKWiz

Could easily go $50 000 + in a short time and that's if they don't find any niggle drainage issues.

Thanks all.
Given the lack of a straightforward solution, and the probable cost not just of retaining, but clean fill, we went for a different option. Picked up a beautiful block in Aveley for $260k

[rare ss]

Originally Posted by Crazy Dazz

Thanks all.
Given the lack of a straightforward solution, and the probable cost not just of retaining, but clean fill, we went for a different option. Picked up a beautiful block in Aveley for $260k

Welcome to the Valley!