# Forum Home Renovation Sub Flooring  Quote to excavate strip footings and bored piers

## djmvc

Hi, 
I require strip footings and bored piers, as indicated by my engineer for an extension.  
Soil report showed a classification of M.  
I need 18 bored piers (450 dia X 1700 deep) completed.
And
Approx 34m length of strip footings (SF2) which are 450mm wide and 700mm deep.
And
9.5m length of strip footings (SF1) which are 300mm and 700mm deep. 
Soil would need to be removed and disposed of by the excavator.  
Please note, I have an existing home on this site so access is reasonable by not as good as a clear site obviously. 
The most narrow spot is a setback of approx 2000mm.  
What do you believe I should allow for from a budget perspective for this excavation work ?
Please note, the concrete work I'm keeping separate.  
I'm located in Melbourne.  
I've received one quote of 5k but not sure if this is too cheap or excessive.  
Any thoughts??   
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## Gaza

Sounds like 2 days for say 4 tonne machine plus truck to remove and dump  
5 k not to far off the mark maybe low 4 s but at 5k I would just go with it unless you get another price a lot lower   
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## andy the pm

my thought is to find another engineer, are you building a nuclear power station?

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## djmvc

What is the alternative to the piers and strip footings?  A slab?
Certainly not a nuclear power station Lol - just a basic extension on a house.  I'm not a qualified engineer so what should I be questioning regarding the proposed structure  
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## andy the pm

Whats the construction of the extension? Brick veneer would only need a strip footing of 500mm(deep) x 300mm(wide) for class M. 1700mm deep piers you could probably launch the space shuttle off....Ask you engineer if he has heard of AS2870

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## djmvc

Brick veneer. 
Are you suggesting that bored piers wouldn't be required? And that there would be sufficient support with the strip footings he has specified even though they're slightly wider and deeper than you've mentioned?
The soil report mentioned that there is silty sand until 1600mm, so I've read it that he, the engineer, is going slightly deeper to reach the clayey sand. 
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## andy the pm

No I,m not suggesting that piers wouldn't be required, just that size seems excessive. Your site is classified as M but your engineer appears to be treating it as class P.

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## djmvc

From a depth point of view (of the piers), his engineering (depth) is in line with the soil report. 1700mm is where the clayey sand commences prior to that it's silty sand.
As for the diameter,  450mm is very sizeable is my mind also, but I don't know the calculations etc.  I also don't know about the sheer number of piers requested,  18 seems like a lot, but again,  I'm really not sure. I'll have a chat with him in any instance, but wouldn't mind your view.
Is it the diameter which you feel is overboard?  Or the depth even though the soil type (silty vs clayey)?  Or the sheer number (18) over a distance of approx 44m?  
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## djmvc

18 over 44.  
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## Pulse

The point is AS2870 allows for simplified footings without the use of an engineer based on site classification. M sites don't require such massive footings according to the standard. The problem is that the engineer is spending your money to make sure there are no problems. If it was his/her house the footings might be cheaper. 
cheers
pulse

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## djmvc

Don't disagree pulse, but unfortunately this is where I'm at. The existing home is 107 years old and on 300mm footings with no bored piers. There are no cracks in the house either.
Reality is, it's 2014, people get sued,  engineer will over specify to protect his own interests even if it's at the expense of my $$$  
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## Mike8136

My engineer suggested piers on our build even though they weren't strictly required. The reason was to avoid any movement in the future (in plaster and cornice etc) due to different foundation materials. Ours was weathered siltstone and silty clay areas. If we build to AS2870 the house would settle slightly unevenly and possibly cause annoying hairline cracks. Cheap insurance to add some piers.  
Yours is an extension so I'm sure your engineer is doing the same for you, making sure it won't move relative to the existing house. 
I would say go with it . You can't add piers after and will kick yourself if you have to repair joins down the track. Its not a structural issue, it's aesthetics. 
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