Issue with steel and foundation

Hi All,

I am at the beginning of a garage conversion. Had drawings by se for steel, got builders out for quotes etc etc.

The garage is part internal. Its a double garage, it supports the first floor via a wall which is in the middle part of the room. The builder that i choose was the only one to come and inspect the job before quoting, he removed plaster and inspected foundations on exterior wall. Foundations were only 250mm so he referred me back to se. The external wall is only single story. It would now be carring the front corner of house with the steel.

SE saying need to underpin, on clay 900 x 600 for the front elevation. Obviously i want to avoid underpinning due to cost and party wall (detached house but within 3mtr of neighbour property) and work would require access on their land.

So to my question, i know i am reliant on an se to do the calcs for the load but has anyone had experience of poor foundations for a steel, i was hoping there was an alternative like a pillar internally which i do not mind having but how would this be constructed, steel/brick? What foundations would be required?

I am just after some information to better understand my position, also should the se of checked the foundations or is that the builders responsibility.

Many thanks

 

Ok thank you, that option was not offered by se i feel i am having to prompt. Would BCO be able to offer opinion or would they just refer back to se. They have been helpful in changes to the garage floor so i didn't have to dig out the 150mm slab.