Confused over soil report - P and H1 and then UTP

Hi guys,

Would love some advice.

Out soil report came back as "P (Depth of Fill)"

Then H1 (which I presume is under the depth of the fill??).

I spoke briefly to our builder who seems to think this is common and won't be a problem. He said developers often fill the land to make it flatter which is why it got the P rating initially. Is this true or is he trying to sell us a house??

The other thing I don't understand is at about 1m depth it says it encounters rock and then shortly after "Unable to Penetrate". Is this normal or a concern?? Sounds concerning to me!

Hi EmyN
The P stands for Problem. It means that the engineer needs to consider his slab design carefully and design it accordingly.
The H1 is a new classification that started last year and refers to the soil type used as the fill. It indicates a high clay content and subject to large fluctuations in movement when wet (swell) or dry (shrinks)
The rock at 1 metre depth is good structurally for slab. The engineer will most probably design a raft slab with concrete piers sitting on the rock platform and then supporting your slab. The slab will also need to be designed to resist the swelling and shrinkage.
I have seen some engineers make builders remove all the H1 and replace with controlled fill compacted in layers. This would be a better solution.
The other problem you have is the depth of services. If you have to dig any sewer or stormwater into the rock then it will be expensive.
All these things mean variations to the builder which means $$$$$ out of your pocket.
If I were you I would get an engineer on board before you purchase the land.
I have just recently been through the same thing. The purchase of the block was based on a favourable geotech report. It came back P so we pulled out.
We are still searching for another block.
If you already own the land then definitely speak to the builder again.
DON'T SIGN A CONTRACT WITH THE BUILDER until you know exactly what cost is going to be.
You might even re-consider a different design to reduce site costs.
Hooroo!

Hi,

I'm reading with interest as I am waiting for a soil report to come back at the moment. Is http://www.engineersaustralia.org.au/si ... _part1.pdf still relevant?

Cheers,
Dim

Yes it is still relevant. They only add regular little updates to make us buy the AS again.

Thanks.

Thanks very much Greenify.

I'm terribly depressed. Our builder (big project mob) has basically informally come back and said it's likely that the rock at 1m depth, and the H slab required will add 30k to the site costs. On the other hand, the realtors have told me that similar rock on our neighbours was "rippable" and didn't add significantly to the site costs. They are obviously trying to sell us the land though...

I can't figure out how to get this possibly massive site cost detailed/pinned down further without commiting to a builder survey/plan which would cosat $1500. It kills me to throw this beautiful land away on an offhand quotation from the builder (when the realtors say it wouldn't be that bad at all) ... but I guess it's what we'll have to do....

Any thoughts anyone?

As nice as they are, I wouldn't trust the real estate agent. Ask them of they are prepared to insure you against cost increases due to the rock. I suspect we both know the answer without asking!

Can you ask your neighbours?

Cheers,
Dim

Check with council or neighbours they will have an idea of what costs are associated. Another solution is build up. If you can replace with compacted fill and get suitable clearance depth for services you should have no issue. I wouldn't trust the agents. The geotec with the degree is the one you should be trusting.
In answer to your questions yes this is common but compacted fill is what you will need.
How many bore logs were completed and was rock found at all of them.