Site costs

annie88 · Apr 22, 2020 12:04 pm

Currently I don’t have the engineering report yet. The builder inclusion is quoted up to H1. My soil test is H2 but developer has provided level 1 compaction report. According to the builder while the engineering report/drawing is not back yet, preliminary report is I don’t need H2 slab and would only require edge beam in garage and piering in garage that’s now been quoted around $2400. It’s a double storey narrow house. I was told H2 slab is not needed but can I request it to upgrade to H2? What’s the estimate cost to upgrade from H1 to H2 slab?

StructuralBIMGuy · Apr 22, 2020 12:57 pm

If these guys (mango shushi) price it up you in for a laugh... enjoy the comedy
Slab Classification
Get proper engineering/geotech report/ Drawing/Details
Cheers
Chris

alexp79 · Apr 22, 2020 1:33 pm

Yes, Chris is right. This is engineer's call, not builder's call to decide.

annie88 · Apr 22, 2020 1:37 pm

Hi Chris. Thanks for replying. I am after a fixed price build and fixed site cost from them. I won’t sign unless it’s fixed price contract. If the engineering report does come back accdg to what the they’re telling me now that it doesn’t require H2 slab, my concern is the foundation strong, should I believe what the engineer is saying if indeed they re classify it below H2 based on the level 1 compaction report?

What else do I need to look out for?

Thank you..

annie88 · Apr 22, 2020 1:37 pm

Hi Chris. Thanks for replying. I am after a fixed price build and fixed site cost from them. I won’t sign unless it’s fixed price contract. If the engineering report does come back accdg to what the they’re telling me now that it doesn’t require H2 slab, my concern is the foundation strong, should I believe what the engineer is saying if indeed they re classify it below H2 based on the level 1 compaction report?

What else do I need to look out for?

Thank you..

annie88 · Apr 22, 2020 1:43 pm

My plans has been submitted to the engineer and as per what the builder told me engineer has told them what was needed for the build in terms of footings but the formal report is not back yet so I can’t really see what’s written. I was told that the contract will be fixed priced including footings required.

alexp79 · Apr 22, 2020 1:45 pm

alexp79 · Apr 22, 2020 1:45 pm

In that case ask for a preliminary report from Engineer.

annie88 · Apr 22, 2020 2:17 pm

I have asked them to send me the preliminary report. The builder is firmly stating it will be fixed price contract including site cost. Unless of course I add or change something with inclusions. I was verbally told that from H2, it has been classified down to H1 with the compaction report. I do want to sign the contract soon but want to make sure everything is ok with the foundation/footings.

StructuralBIMGuy · Apr 22, 2020 8:03 pm

Hi annie88 fixed price contract is the way to go.

Our friends/members on homeone would be curious as to how your Waffle Slab or Stiffened Raft Slab and site works for H1 with Piers on controlled fill equates to $2400?
Most battlers and punters over East pay $50K here
Site Costs-Please advise
Thanks for the reply
Cheers
Chris

annie88 · Apr 22, 2020 8:32 pm

Hi Chris. Their standard inclusion is quoted up to H1 class. The build cost that was quoted to me includes that. Other thing they flagged prior was that might require piers was for the garage at boundary wall. Which is what the $2400 is for now. Anything above H1 I will have to pay as an upgrade. It is a waffle slab. I have limited knowledge on this hence the post in the forum...

StructuralBIMGuy · Apr 22, 2020 9:59 pm

Hi Annie,
I suggest you get the engineering and check the contract documents properly if you have limited knowledge
Forearmed is forewarned
Cheers
Chris

insider · Apr 22, 2020 10:33 pm

Hi Annie
Not sure how you can have a H1 slab sitting in fill and then put piers in one section down to natural soil. You will end up with differential settlement. Can you supply more information ?

alexp79 · Apr 23, 2020 1:47 pm

If he has L1 compaction report, most probably the soil has been replaced/added, as otherwise what was the whole purpose of compaction?

But I agree with insider, you can't have piers just on one side.

Another important aspect is that on the reactive soil piers are to be connected to the rest of the slab with the steel reinforcement, I am struggling to understand why no one is actually doing this! When/if water gets under the slab, it will lift the slab up and the dirt will get in between piers and slab, so eventually you can still end up in a slab heave as the amount of dirt may not be proportional. I guess the whole idea of the piers was to make sure that due to their friction with the soil they will be limiting slab movements both up and down, not just down.

alexp79 · Apr 23, 2020 2:04 pm

so what is the logic behind here?

If I am not missing anything, one of Cornell Engineering guys in his blog was talking about necessity to connect piers to slab?

upd: ah, I see it now. a piece of flexible rubber to prevent dirt from entering inside? Still doesn't help with using piers to prevent the movement itself.

annie88 · Apr 23, 2020 2:26 pm

Hi. Thanks to everyone who replied. I will just wait for the final engineering report and update here. So far that's all I know about the piers and edge beam on garage side (built to boundary wall). I will ask re why not pier all over and why only one side.

My soil test states : Classified as Class H2 in accordance with AS2870- Residential slabs and footings

Predicted surface movement (Ys): 55-65mm
Field moisture content ( % ) : 24.1

Fill Depth: Approx. 2.3m BH1 & 2.2m BH2 (Level one certification sourced)
Soils: Refer to borelogs
Foundation material: As above (all footings to be founded on uniform materials)

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Please let me know what you think? What else I can ask once I get the engineer's report? What should I expect in terms of, for a waffle slab on a H2 or H1 what needs to be there. Total area is 242sqm for double storey.

Thanks in advance

alexp79 · Apr 23, 2020 2:34 pm

do you have data from the lab?

annie88 · Apr 23, 2020 2:45 pm

alexp79

do you have data from the lab?

Hi Alex. May I know what you mean by data from the lab? That's all that was given and copy level 1 certificate.

alexp79 · Apr 23, 2020 2:46 pm

there should be information from the lab on the soil sample analysis (as they have sent 2 samples to the lab according to the above). Based on what they classify it as H2?

But nevertheless, it is FILL clay sample which is classified as H2, so you really can't be H1.

annie88 · Apr 23, 2020 3:05 pm

alexp79

there should be information from the lab on the soil sample analysis (as they have sent 2 samples to the lab according to the above). Based on what they classify it as H2?

But nevertheless, it is FILL clay sample which is classified as H2, so you really can't be H1.

I didn't get copy of the lab result, I can't see it on the soil test result. It says on result on the basis of the site investigation including bore logs, dynamic cone penetrometers and NATA Accredited Laboratory analysis the above site may generally be classified as Class H2

I will wait what is written on the engineers report and go from there. I won't sign the contract until I am satisfied with the slab specification..

For a H2 on a waffle slab, do I need piers on all areas? I have been searching online, it says to ensure stronger, deeper, and stiffer footings but what does it usually involve?

Thank you