Single storey extension foundations

[JasonBee]

Hi
I have an existing conservatory(3mtrx3mtr) which I would like to change to a single storey extension.I have done a sample dig to measure the depth of the concrete slab which is 300mm thick,finishing at ground level.The surrounding ground is primarily clay.Is this slab deep enough or will I need to underpin.

Any input would be grateful

 

[dann09]

Research posts and google ref. foundation diagrams and requirements for single story extn.

 

[noseall]

I have seen buildings constructed on less!

However it is unlikely to satisfy building control unless you can get a suitably qualified person to say that it is ok. a typical raft would be say 450mm at the edges and say 200mm in the middle but would all be knitted together with reinforcement.

If it was me i would bite the bullet and hoof it out.