# Forum Home Renovation Sub Flooring  black soil

## manofaus

I am lookiong at a block of land in the upper hunter and it happens to be on black soil. I talked to a neighbour and he said when his shed went up they bored 5m and still did not hit anything solid. The house that we want to build will have piers so what will the cost of the footings now cost compared to a class m soil? what will they need to be, deeper, wider, more mesh.. We will be owner building our own house design. Should I avoid it like the plague?
thanks

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## jago

The cost is really dependant on the design of the house as this will determine the number of piers and placement. Talk to the local building/concrete companies they should give you an idea of the design requirements for the area....if they're are any new builds at footings stages have a sticky. Ultimatley an engineer is going to have to design the footings. 
For my small reno I required 5 piers and they where 450mm dia by 2 metres or 0.9m3 of concrete about $200 per hole plus steel etc. :2thumbsup:

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## manofaus

was that for class h soil? did they hit hard ground after 2 m?

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## intertd6

You would be needing steel screw piers if putting a slab on ground, If using strip footings they would be a deep beam design or bored concrete piers if no strip footings needed, design your own footings from the standard once a soil test is done. All standard stuff for housing west of the divide in NSW where black soil can be in places + 100m deep
regards inter

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## Bloss

:What he said:  but first thing is to get the soil tested as said - the colour is not an indicator of stability. There are black clay soils, black loamy soils, black sandy soils and black soils which are high in humus so are not great for carrying loads. A suitably designed floating slab will work fine on pretty much any soil type. The question is usually one of least cost to do the job and one soil type (or mixed across a site which is not uncommon) might demand a higher cost solution than another type. Test bores of 5m will tell you what the nature of the engineering design might have to be, but does not mean you need to take footings down to solid ground (on a residential building or shed) - there are many structural solutions that would be appropriate.

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## sawtooth

dalby in southern Qld (yeah; just been flooded) has _very_ deep black soil and building movement is a real problem and they often use very deep concrete piers and  adjustable beams. I'm pretty sure a builder there sort of invented the screw adjuster that make it easy to keep the building level and straight. 
Not sure if that is any help in your area but I would think all info is helpful in one way or the other. 
BTW I have not lived in dalby for a while now

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## Bloss

As said - best to see of there is a problem with your specific site first then look at the options  .  .  .

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## mark53

What Bloss said is good advise. From what I understand, and irrespective of what foundation you use, ensure you have superior drainage.

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