[shack]

I would have a chat to any engineers you might know or be able to be put incontact with first.
Hydraulic, civil & structural. I'm sure there is a little more in it then building a "pool" but hey it sort of makes sense.

Will need access for when or if it fails plus maintenance.

Are you close to the water? Water table heights will make it interesting. Last thing you want underground is a Ferrari and rising ground water.

Also be mindful of services coming into your property i.e. Electrical sewer storm water.

Totally agree and no not close to the water and my pool went in with no issues. These days with IP based sensors that are available I am sure I can install enough early warning stuff just in case (camera's, smoke and water sensors etc) in addition to a small diesel gen.

[looney]

I'm sure there is a little more in it then building a "pool" but hey it sort of makes sense.

Yeah it is different,  but you could quite easily apply the same excavation techniques.

In all honesty if it were me,  I'd sheet pile the area,  membrane then cast concrete in situ.  It wouldn't be the cheapest way to do it,  but would be the least troublesome and would be ideal for a zero lot style installation

[looney]

As for drainage, that's obviously site specific.  Simplest option would be if there was nearby storm water at a lower RL than your pit, beyond that you could sump pump.

The bigger concern in reality would actually be ventilation. If you had an access stairway there is a very real possibility a pit like that could become your very own crypt.  A sealed below ground box housing a car full of vapour causing fluids could potentially overwhelm you if you went in there.  So a good ventilation system would be critical

[Joel]

Yeah it is different,  but you could quite easily apply the same excavation techniques.

In all honesty if it were me,  I'd sheet pile the area,  membrane then cast concrete in situ.  It wouldn't be the cheapest way to do it,  but would be the least troublesome and would be ideal for a zero lot style installation

Yeah then you're essentially building a basement car park. I'm not sure how the vibration for sheet piling would have an impact on the neighborhood. I've only used it on a big open paddock.

[goober]

It's the sort of thing you would do because you love gadgets, but it would never stack up from a financial point of view.  Digging holes is expensive. Having the top car uncovered in the elements makes no sense anyway. Surely there are better stacker solutions than that one.

i'm having plans done to build a new house with car elevator and room to hold 10 cars on the bottom floor with concrete roof/ ceiling and perspex panels in the concrete so cars can be seen from ground floor.
Digging is expensive if its to existing building, starting with a blank footprint is also expensive but tax deductible if structured correctly.

[360c]

No chance of that. Dude even this is an UBER stealth project as wife would kybosh it in 30 seconds. I need to send her away for a few weeks and then just do it

Good to know that I'm not the only one who operates like this, all my big and expensive projects get done this way. If the wife gets involved it is a guaranteed fuck up, or more likely a non-starter
Better to plan it all and then suggest she "needs" a holiday, preferably with the kids 

[looney]

Yeah then you're essentially building a basement car park. I'm not sure how the vibration for sheet piling would have an impact on the neighborhood. I've only used it on a big open paddock.

We use it regularly in the burbs. Delap survey surrounding properties and away you go   we've not really had many issues

Other option is concrete piling but that's more $$$

As you rightly know each individual situation is different.

[360c]

Going underground is big bucks, we have lots of it happening in my area despite relatively large (these days) 1000 sq mtr blocks. A mate is involved in local  residential and smaller commercial developments and I often hear him talk of $300k + basements.
I know of one 20 car garage in Toorak that supposedly cost $2.2 million at least 10yrs ago.

[shack]

Yeah then you're essentially building a basement car park. I'm not sure how the vibration for sheet piling would have an impact on the neighborhood. I've only used it on a big open paddock.

As for drainage, that's obviously site specific.  Simplest option would be if there was nearby storm water at a lower RL than your pit, beyond that you could sump pump.

The bigger concern in reality would actually be ventilation. If you had an access stairway there is a very real possibility a pit like that could become your very own crypt.  A sealed below ground box housing a car full of vapour causing fluids could potentially overwhelm you if you went in there.  So a good ventilation system would be critical

Very helpful and thanks

[diabloinoz]

Very helpful and thanks

One of the biggest issues round here is Acid Sulphate ... if the ground is acid sulphate that you're taking out ... it needs special treatment when you're dumping it and costs 3x as much.

Hence get a soil sample done and know for sure ... or check your local council planning dept maps.