guess at the foundation, earthworks, pilings

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driller2000

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#2002099 25-Apr-2018 10:04

Civil engineer here....

As others have said get a geotech report done - this is ESSENTIAL for a sloping site.

If you know someone in the building/earthworks trade you could get them to comment on your plans and give thumb suck estimates (Note: Think in multiples of $100k additional - eg. we spent $60k 10 years ago on cut to fill + import for 40m of retaining with an average retaining height of only 1m - and minimal additional foundation work - you will require a truckload more. And prices have "doubled" + since we got our work done.)

Also - sloping sites are "cheap" for a reason ie. because they are difficult/expensive to develop - incl access, earthworks, retaining, drainage, foundations, structure - are ALL more complicated - which equal lots of $$$$.

Aredwood

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#2002104 25-Apr-2018 10:19

Also consider council rules for driveways. As some councils require you to provide space for you to turn your car around on the property. As they assume that you don't know how to reverse your car into the street.

I'm assuming that the street is in the top part of your sloping land. It might be far easier to have a separate garage or open car park at street level.

And also very important. Check where the council sewage and stormwater pipes are. Big money to pay to relocate them if they happen to run under where you intend to build. And also can you get gravity drainage into them. Or do you need pumps? And under Auckland city council, they sometimes refuse to allow stormwater pumps. So if no gravity stormwater available, the only other option is convincing the neighbors to allow you to put an easement on their land to run stormwater. Which they will probably deny. Meaning no building or being forced to build a much smaller house.

kingdragonfly

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#2002156 25-Apr-2018 11:50

All good advice. Cheers.

I'll give it a skip.

The owner is "flipping" the lot, which is annoying: about 50% increase in two years, bought at $120K trying to get $180K.

Here's the property, between Porirua and Wellington, if anyone's interested.

https://www.trademe.co.nz/property/residential/sections-for-sale/auction-1540757376.htm

kingdragonfly

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#2002161 25-Apr-2018 11:57

One last question.

I hate yards. The perfect house would have zero gardens.

I'd love a home on just piles, suspended over an incline, with a great view.

Are there any rule of thumbs about piles?

pipe60

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#2002301 25-Apr-2018 14:04

We built on a sloping section, as above get the geotech report first then you can sort out the earthworks by the time we had finished it was around $65k for the pad above for a 400M2 house.

Fred99

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#2002323 25-Apr-2018 14:45

kingdragonfly: One last question.

I hate yards. The perfect house would have zero gardens.

I'd love a home on just piles, suspended over an incline, with a great view.

Are there any rule of thumbs about piles?

One casual anecdotal observation. We live in a small lane on the Chch hills which had 7 dwellings in it (now only 5). The houses on piles (including one "pole house") survived (with varying amount of damage), the slab on grade houses apart from one are now part of the hard-fill used for land reclamation at the port, the one that did survive needed about $800k of repairs.

Repairs to damaged piles and perimeter foundation damage at our place cost less than $10k.

Two of the slab on grade homes were relatively new (2005 or so).

There are of course pluses and minuses, but for a sloping site in NZ, I like the idea of piles / pole houses.

A comment about that section for sale - they make a point of mentioning "With completed designs and resource consent in place", these aren't plans and it's not building consent. It's when you engage designers or architects, to draw up plans for submission to council that geotech is needed - those professionals will know what's needed, but Councils may still get extremely pedantic and want more before they grant consent, rejecting the application with an "RFI" for more expensive geotech, which probably means more $$$ for engineering design and building costs. My guess is that the owners may have got close to that stage, found out how much it's going to cost - and are bailing out.

kingdragonfly

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#2002382 25-Apr-2018 15:51

For anyone interested in a NZ pole house, I found this web page with lots of pictures.

"Sustainable pole house, Whangamata"

http://www.beachhousebuilders.nz/gallery/sustainable-pole-house-whangamata

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neb

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#2002432 25-Apr-2018 17:14

wellygary:
There is no way you can tell any of this until you get a geotechnical report on the site,

What is the soil, is it cut or fill, what is the general slope stability of the area, etc, all will impact on the design of any foundations....

... when was it built, is it cheap/moderate/expensive, ...

neb

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#2002439 25-Apr-2018 17:19

kingdragonfly: One last question.

[...] Are there any rule of thumbs about piles?

More fibre in the diet, and liberal application of Preparation H.

kingdragonfly

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#2002479 25-Apr-2018 19:41

I knw that was coming, five seconds after I posted it. :)

Fred99

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#2002519 25-Apr-2018 21:03

neb:
kingdragonfly: One last question.

[...] Are there any rule of thumbs about piles?
More fibre in the diet, and liberal application of Preparation H.

Or a suppository, with the proviso that if you chew them instead of just swallow, then you may as well have shoved them up your a^$@ for all the good they'll do you.

kingdragonfly

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#2003278 27-Apr-2018 08:50

Looks like the retaining wall would be about $100,000 best case.

Plus piles would be about $200,000 best case.

Plus more earthwork.

I also don't like that fact there's a creek on the property, a couple of meters below house line.

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