Hi There,
We are building on top of a demolished house site. The original house subsided due to uncompacted fill and poor drainage.
The soil samples show uncompacted fill to 1mt depth. ( No idea why this would of been done it is a 10 acre flat block ) Class H1 - D, P. (lucky us)
To compound this we need to raise the FFL 500mm as we are in a newly appointed 1:100 year flood plain.
The engineering is massive, being reinforced raft footings continuously trenched 200mm into natural ground. The footing has been designed for uncontrolled fill.
We need to bring in 500 Ton of fill. The builder has some fill but not enough from a development 25 kw away.
They have included the fill in the price, but we will need to wait until they can get it all. Or we can pay extra for quarry rubble.
We have a quarry 5km away that can supply:
Quarry rubble @ $20 +GST a Ton
Under foundation sand @ $12 +GST a Ton.
The explanation of the under foundation sand, sounds like crusher fines. They say they sell it for specifically for that purpose. This would work out to be $6600.
There is also limestone rubble available from another nearby quarry. A local builder had mentioned that this was good as a base. I thought it would still be quite reactive though?
So my question is:
What is the best fill to use on this site?
If the builder was to say it will take 6+ months to get the fill, we will most likely pay the extra as we are in our rental property losing rental income, so it balances out.
I would prefer to negotiate with the builder to use the under foundation sand instead of the fill as I suspect the fill will most likely be a high clay composition, as is most of Adelaide.
Thanks for your time,
Regards,
Clayton.