How much below groundlevel to fill the concrete?

[slough200]

Hi All,

I wonder if you might be able to help. I am having outbuilding built in my rear garden & having the foundations done. We have filled the foundations with concrete but aren't entirely sure how far below ground level we need to stop the concreting. The building regulations plan I have from the architect onlys says "trech fill foundations 600mm wide"...any ideas?

Also what needs to be put on after the foundations are done?

Thanks in advance.

[stoneyboy]

slough200,
Impossible to answer it depends on sub-soil conditions and what you are going to build ontop of the foundations.
end