driveway design - ground conditions

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nickreno

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#295321 21-Mar-2022 13:31

Hi! I'm trying to figure out which professions to engage to get a driveway designed, to extend a driveway into the rear yard. Good ground (for building) is approx 1m below the current ground level, and I'm not sure if this means things need to be excavated a lot, of if there are other solutions around this - what sort of profession would usually do this sort of design work? The earthworks contractor I've spoken with seems comfortable excavating and then compacting, but I'd like to double-check as unnecessary excavation is expensive due to site access issues....

nickb800

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#2889573 21-Mar-2022 13:45

Structural engineers do this sort of thing all the time for building platforms - assessing ground bearing capacity and designing foundations given a specific design load. So I'd try your structural engineer first, and if the ground is a bit special, then they may refer you onto a geotech. Either way you could end up with a 6+ month wait given workloads at the moment.

It depends how much money is at stake, but an alternative approach would be to ask your earthworks contractor what sort of house foundations are typically built in your area (on the same sort of soils). It might be a reasonable trade off to just pay the contractor to build you driveway like a house foundation, rather than wait and pay an engineer to tell your contractor to build it like a house foundation. Hard to say without knowing site specifics, but given your description I'm guessing standard 100mm concrete with mesh on 100mm basecourse won't cut it. But if all the houses around you are built with ribraft/waffle type foundations then you could get your driveway quoted on that basis.

nickreno

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#2889653 21-Mar-2022 16:18

thank you, that is great advice - will have a look at similar recent driveways on the street -

mattwnz

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#2889673 21-Mar-2022 17:19

Just getting someone to build a driveway these days seems to be nearly impossible.

Jase2985

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#2889734 21-Mar-2022 20:58

mattwnz:

Just getting someone to build a driveway these days seems to be nearly impossible.

correction, in a reasonable time frame. its probably about 4-6 months at the moment.

mattwnz

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#2889749 21-Mar-2022 22:04

Jase2985:
mattwnz:

Just getting someone to build a driveway these days seems to be nearly impossible.

correction, in a reasonable time frame. its probably about 4-6 months at the moment.

No, my parents have been strung along for over a year by one driveway company who previously said they would get it done by Xmas.. They have also gone to others but can't even get anyone out to quote and then they maybe waiting until the later part of the year with all the work. People don't want the work and then people also risk getting ridiculous quotes by companies trying it on and taking advantage of the current situation.

johno1234

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#2889866 22-Mar-2022 08:21

mattwnz:

No, my parents have been strung along for over a year by one driveway company who previously said they would get it done by Xmas.. They have also gone to others but can't even get anyone out to quote and then they maybe waiting until the later part of the year with all the work. People don't want the work and then people also risk getting ridiculous quotes by companies trying it on and taking advantage of the current situation.

Yep, have run into this myself with concrete work and driveways. Plenty of big new jobs to do, so small jobs or those that require removing of old driveways are of little interest.

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Jase2985

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#2889867 22-Mar-2022 08:23

Absolutely not my experience in auckland

johno1234

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#2889878 22-Mar-2022 09:17

Jase2985:

Absolutely not my experience in auckland

Who you used, Jase? Good guys I've used in the past are just not interested in little or fiddly jobs.

Jase2985

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#2889879 22-Mar-2022 09:19

depends on what you call a little or fiddly job?

Mine was remove about 160m2 of old drive and place 140m2 of new drive

johno1234

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#2890022 22-Mar-2022 13:08

Jase2985:

depends on what you call a little or fiddly job?

Mine was remove about 160m2 of old drive and place 140m2 of new drive

Would have thought that's a decent job as far as residential goes. May I ask rough cost /m2 to remove old drive and build new - 100mm with mesh? Builderscrack estimator tool has this somewhere between $24k and $45k

My next project is about 230m2. The driveway is only about 40m long or 120m2 but there's quite a large turn-around area at the top which greatly increases the area.

In our case we have a large but moderately sloping rear lawn so am thinking of placing the broken rubble there, creating a batter to level it all off. Adds machine+labour moving it from one side of the property to the other, not sure how much dumping cost that saves.

Jase2985

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#2890029 22-Mar-2022 13:21

Less than your lower amount and the concrete was coloured which added another $1500 to it

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thenine

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#2894200 30-Mar-2022 12:57

nickreno:

Hi! I'm trying to figure out which professions to engage to get a driveway designed, to extend a driveway into the rear yard. Good ground (for building) is approx 1m below the current ground level, and I'm not sure if this means things need to be excavated a lot, of if there are other solutions around this - what sort of profession would usually do this sort of design work? The earthworks contractor I've spoken with seems comfortable excavating and then compacting, but I'd like to double-check as unnecessary excavation is expensive due to site access issues....

How are you going with this? I design this sort of stuff as a day job so I may be able to help you out. I usually design for industrial loading but this is the same just a smaller scale. I do have a couple of things for you to consider.

Soft ground isn't necessarily bad. As long as it's all soft. All soft or all hard = good, a mix of both = not so good. Concrete generally doesn't respond well to differential stiffness in the subgrade. We can design that out though. Not sure about the site itself, but it's worth considering fibre cement, it's relatively cheap, suits most domestic applications and saves on labour costs vs mesh. Joint location is quite critical especially on soft ground. If they're not frequent enough or if they're in a bad spot it can lead to uncontrolled cracking on your nice new driveway. Also, consider the vehicles using it, if you're rural and going to have the odd truck travelling over it, it'll be worth beefing it up a little, if it'll just be used for cars and utes, then you'll probably be fine with 'the standard' 100mm thick slab. Lastly, Subbase construction and compaction is the most important aspect here. For alot of contractors it's an after thought, but it can save alot of headaches in 5 years. Saves you dealing with slabs at wacky angles and level differences.

In terms of building it. I'm not much help. Most domestic guys are under the pump right now. You might be able to find a small-medium size civil construction firm to help you out. Coming into winter they can lighten up a little so you may be able to catch them between jobs or before they move into maintenance season.

nickreno

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#2894228 30-Mar-2022 13:28

thanks - am still seeing what I can learn - but the general idea to follow what neighbours have done was, although so obvious in retrospect, really helpful. I know that the ground beneath the topsoil has a 200KPA bearing capacity, and this increases to 300KPA after approx 1m further depth - I'm not even sure if this still qualifies as "soft" or not. I will 100% speak with the driveway contractor around fibre reinforced concrete, this also sounds like a really good idea.