Foundations cost

[Laguna343]

Hello I am currently having a first floor extension built. 4m x 3m

They started digging for the foundations only to find that the ground immediately outside the house is a hole filled with rubble.

The building inspectors therefore told them that they will need to dig out the entire area. Fill with stone and compact it.

Concrete and steel slab on top.

Something along those lines

Does anyone here have a rough idea of how much this may cost.

I'm sure its going to be no small amount.

Its in Yorkshire and the Humber region.

Thanks

 

[tomfe]

So the ground where the slab is going is filled with rubble or the ground outside the foundations?

 

[Laguna343]

So the ground where the slab is going is filled with rubble or the ground outside the foundations?

The garden lawn is all clay underneath. However the area between the house and the garden lawn (which was paved) has turned out to just be a hole that they had filled with all manner of crap.

This rubbish filled area is where our extension was meant to be being built.

 

[wessex101]

What depth/type of foundation is the original house built on?

How deep is the rubble fill? It might be cheaper to dig through the fill and have slightly deeper foundations than a reinforced concrete raft foundation.

 

[^woody^]

You need to stop and assess the options, and not just listen to the building inspector.

Building inspectors are not foundation desingers, and I can't for one minute think that a foundation on compacted stone is at all acceptable.

 

[garyo]

Laguna : are you clear on the difference between the slab and the foundations? This has a huge bearing on the question you're asking.

When you say 'steel in the foundation' do you mean 'mesh/rebar in the slab'?

I suspect your foundations are probably fine and this is all about the hardcore under your slab.

 

[wessex101]

Laguna : are you clear on the difference between the slab and the foundations? This has a huge bearing on the question you're asking.

When you say 'steel in the foundation' do you mean 'mesh/rebar in the slab'?

I suspect your foundations are probably fine and this is all about the hardcore under your slab.

I was thinking the same thing and wondered if he meant a suspended reinforced concrete floor slab but gave him the benefit of the doubt. The floor slab would make more sense.