1920s chalet bungalow. Original foundations insufficient

[LaCurandera]

Hi, 

We've got a 1920s chalet bungalow (currently 1.5 storey). Three main areas of the property:

The side extension (1960s) has foundation that are approx. 250mm thick.

 

The rear extension (1980s) has foundations that are approx. 600mm thick into good ground.

 

 

The main bungalow (1920s) appears to have very unsubstantial flint footings, not more than 150mm thick

 

Ideally, we don't need to build over the extensions, but would like a proper second storey (either timber or brick, not) with pitched roof which would be on the original walls and then extended out the back so would be new there.

We're waiting on a call back from a SE early this week, but is there any comment here whether this kind of foundation is ever saveable or workaround for an extension option? Is demolition likely to be the only real option?

 

[George]

The likely recommendation would be to underpin. A ground investigation to minimise the extent of the underpinning could be money well spent.