Crack on the soil beside my Single story new extension(no trees around)

[Mubbashshir]

Hi All, 

 

I am still working on the final bits with the builder. This small single-storey extension has developed a crack in the soil, although it's a bit away from my wall. However, there are no cracks in my wall or any problems like opening or closing the doors. Please note that this is built over a soil pipe. I am a bit suspicious that the builders might not have put a concrete slab in the way they laid it to bridge the cavity over the pipe.

 

Also foundation is good size i.e. 750 wide mm and 450 mm deep based on calculation done by structural engineer. This crack wasn't there before or may be gradually became more apparent. Also attached are the pictures of foundation which you can see clearly how deep the foundations were. 

 

Reasons for cracks: 

1. Is there anyother checks to be done on new extension or existing building to ensure this crack does not expand and cause any further problems.

 

 

What next steps should I inform my builder or insurance company asap

 

 

 

Edited Sunday at 11:38 by Mubbashshir

[Spinny]

Was the DPC inspected by building control because one of your photos raises questions in my mind, but others may know better.

[Redbeard]

It's a very non-scientific 'diagnosis' but if you look at the shape of the left-hand-side of the empty footing trench the crack seems roughly to follow that shape, suggesting that the crack is between the existing (pre-extension) ground and the (presumably softer, less compacted) fill. 

[Jenki]

I'd suggest the extreme dry spell has shrunk the less well compacted backfill.  Nothing to worry about. Unless brickwork etc starts to crack that is.

[saveasteading]

I think it is simply poor backfilling....pushed in and barely compacted. The fill has shrunk away from the untouched ground.

It seems to have come away from thd wall too.

The only concern is that rainwater  will run through these gaps very quickly. Nothing terrible will happen but I'd get them back to compact it better. It will be character building.

[Temp]

Looks like the soil is clay? This can shrink and crack quite a lot.