Concrete estimate was too low for slab

Hi all,

I'm coming towards the end of my build - whiles for the most part it hasn't been too bad I have an issue where the builder has passed on some variation costs...

Some are reasonable some are not.

My architect has told me to pay the extra concrete in protest.

From what he told me they should quote with a 10% margin of error (they quoted 76m3 in the contract) though charged for 108m3 + Margin.

When I first read the contract I mentioned this as an issue as it was off on my estimate, but they said it was about right. I spoke to 2-3 previous builds and they were all under quoted for concrete.

Is this something I should contest as it's about $5k in it. (Rock removal was charged at 15m3 (there was no more then 5-7m3) at most.

They have also asked for a 5week extension to build time which is at a cost of $750p/w which they won't want to pay

One other issue I have is the plumber only put in one LPD (in the plans it specifies two) the builder assured me this was fine and would be approved by CWW (though it wasn't part of my engineering).

Anyhow is the 10% tolerance on concrete acceptable or do they have the right to charge the whole amount?

I would insist on the 2 ,and only give in when they become reasonable with their gouging tactics which is a complete con,no way would u miss concrete estimation by 50 percent, doesn't matter that builder say's one is ok,contract says 2,so use this to get them.down.

Not sure of the engineer requirements in Vic, but I use m2 of slab x 0.16 for an M Class and 0.2 for a H Class, eg: 200m2 slab x 0.16 would require 32 m3 of concrete for a M Class slab design

Aside from brining it up with the builder, what are the legal grounds or VBA that would justify it?


I can’t seem to find the 10% which my architect mentioned?

As you are using an architect then your contract administration should be by the architect.If the payment to the builder has been certified then payment is due.
But it seems its more complicated than that
Experienced building consultant in contract administration should help you.

No contract admin, just me.

It’s him reminding me that I should’ve paid for his services...

Which in hindsight would’ve saved some headaches...

That's is why Battlers and Punters Don't use Architects nor trust builders estimates...
LOL in a nut shell they cant afford mistakes.
Seriously, how can the concrete estimate be 50% under?


The builder would have picked up the mistake..and an unscrupulous person would have taken advantage with a lower bid..
I would make the Architect pay as he is the professional not you?

REASON
OT, They use 3D BIM Model renderings to sell you the project, virtually build it ?
... could'nt they have also checked the key element material quantities
ie, Concrete, bricks, Roof, gyprock?

Here i use the same 3D Software that architects/Builders use
the difference is no body gives a sh!t on site
about the renderings as we are more concerned about the engineering and what gets built on site,eg
Slab and formwork Costs

please excuse the rant, 3D bim tools exist to avoid costly on site mistakes,
next time find an architect that knows what they are doing and never sign a cost plus contract without Engineering 3D BIM
Cheers
Chris

Sorry I think there is a miss understanding.


The builder made the quote and the contract.
The architect simply notifies me I shouldn’t pay more then 10% of what they quoted.

There is no contract admin.

It’s a builders HIA contract.

Is it a Cost Plus or Lump sum contract
HIA Online products ?
As BE has mentioned building documents are a mine field to navigate without profession advice
and the HIA favour Builders...not consumers
Cheers
Chris

That’s correct. On both accounts.

The HIA contract is all in the builders favour...

It’s cost plus... $245m3 + 20%

The going over the contract length by 5weeks which they won’t pay is another issue in itself.
(Excuse is CWW changed the water connection points so they lost 3 weeks before they could do concrete drive ways). So that’s $3750 in itself.

The concrete is the big one as is the LPD...

It will save u money by getting a building inspector who understands building contracts ,I would get one yesterday,but u have to make sure the inspector u choose is highly qualified such as this forums building expert who's a Victorian.
Darbbeca maybe if not in Victoria.

If its cost plus, well then its costs plus??? Make sure he gives you delivery dockets showing the m3 used, match that with the invoice and move on. I'm very sure the builder didn't want to put more concrete in or dig up rock or excavate longer.
If there is an agreed rate that you are clearly contracted to then job done.

Normally quantity of concrete used is never an issue unless there is a provisional sum adjustment

I've had blow outs in excavation with rock that has really thrown the estimate of the final concrete. Conventionally you can get it spot on or within reason.

The matter is between owner and the builder. If builder has used more concrete than estimated that's builders risk unless it is a provisional sum and subject of adjustment.

“provisional sum and subject of adjustment.“

Which it is what it was estimated for, that amount...

They removed two large rocks (which they charged for 15m3 (really about 5m3 max).

So even that doesn’t translate into almost 30m3 difference.

It was funny that the concreter ordered the exact right amount with almost no waste to the 1/2 truck....


From what I’m learning there doesn’t appear to be a hard and fast rule that they should’ve quoted within 10%.

As they use the provisional cost to make up some cash. Rightly or wrongly.

Probably has merit to argue...

The LPD on the other hand is a big issue... That may or may not see the light of day.

There is a lot more to building contract adjustment (provisional sums) than you know and no one can give you the right answer until there is a proper review of your contract and the builder's claim.
It seems you have not engaged your architect for contract administration
The chances are you will save hundreds by DIY but drop thousands instead
I have seen it so many times

This is true, though they were charging $8k for contract admin (so a bit more then a few hundred). But would come out even if I opt to use a building inspector I'd say.

I'll look at giving you a call tomorrow in any regard.

Cheers

Excavation blow out is not measured, it's builders risk.