Slab cost

I know slab costs vary depending on the footings but the price we got seems quite high.

The area covered in total is 341.55 m2 with 19.2 of that being a seperate patio.

We're being charged over 40 g's for that and some footings for a retaining wall.
does this seem right?

What does a waffle slab cost in comparison to a raft slab? would that reduce costs as there is less concrete and it can be poured in one go?

What does your geo report say? If you are on a sloping block with worse than moderately reactive soils and some rocks or large retaining walls required this would explain your sites.

theres a slight slope at the back, theres also a long retaining wall 24 m long with footing 500*300 and a lip of 300*1m so the total cubic m for 1 l/m of footing is (0.3+ (0.3*(0.5-0.3)= 0.36 cubes*24l/m= 8.64 cubic metres

If the footing for thre retaining wall is 2m deep say and 500mm wide that would be approximately $10,000 just for the footing for the retaining wall. Then there will be the wall itself, plus other costs. I would definitely ask for a break down of the site costs and query every item. I have seen on this forum that it is the site costs that are a likely area that builders will try to increase their margin.

well the footing on the engineers report is 500 deep but apparently the project manager we have sais thats overkill and the guy who did the report did way too much, more than any other house he's ever built, so i'm not sure if they're doing it with a shallower depth, or whether the depth of the house footings were cut back.

the block isn't really sloping at all

We are owner builders and the surface area of our slab is 325 m2. The cheapest (by far) quote we received was $40,000. Our footings are 300mm wide and 700mm deep.

Our site classification is M-D & P

so that sounds about right then considering the retaining wall footings. thanks for the reply

the footings on the house are about 400 deep and 300 wide so not as deep, but the retaining wall footings would be extra

The slab price has gone up 22 grand as our 'project manager' got the carpenters friends to do it and didn't get a quote. He said he could get it done cheaper but didn't provide any costings or estimates.

excavation costs were higher as they hit rock, however they couldn't have been 20 thousand higher.

to top it off after asking the concreters to stop working on it they went in and put all the steel reo in after we asked them to submit a quote to us so there is all this steel in there ready to be poured and we don't want to go ahead with these concreters as they seem to have over charged for the amount and price of concrete and steel (there are pieces of reo all over the side of the block) and for the excavation as they seem to have charged for more fill removal than is there.

You need to see a cost breakdown or 'break even' cost.

If you know the name of the concrete premix plant,
I am sure you could ring and ask how many Cubic metres were used at your site
Then we/I could possibly work out the labour componant and cost of materials and consumables.
If that would help.

actually now the quote is up to 70 something grand including the blockwork for the retaining wall, but my mum doesn't want to get our project manager off side and wants to start the pour anyway and cop it on the chin.

what kind of project manager doesn't get quotes and contracts with their contractors. the guy doesn't even supervise on site as he's too busy operating another business as a personal trainer while he's getting paid 2thou + a week from us.

A project manager should get contracts and quotes and supervise right?

does anyone know what a project manager charges and what their responsibilities are.

i have a friend who is a builder but cant work as he's at uni and he said straight up you can't build a house without being contactable during business hours by tradies, and you cant leave the site unsupervised as you need to be there all the time to manage the project.

it seems like the definition of project manager is someone who runs the project but this bloke keeps telling my mum he's not supposed to be there all the time because thats not what builders do.

sorry and to the last reply, thanks, but I can't get any information out of this project manager and the concretor hasn't or won't supply an itemised cost list. very professional these guys are.

Just found out that they've put 20 MPA in the footings when 25 MPA was specified so have to contact the engineer to see whether this will be ok. keeps getting worse and worse. these people are idiots.