Lintel specs for masonry wall

I am looking to knock through a single brick wall where at the present there is a single doorway in the centre of the wall. The eventual opening will be in the region of 2.6 metres. There is another floor above and the brick wall continues through this floor to a timber and steel roof. That is to say, my lintel will need to support a 10 foot high brick wall ( upstairs wall, single brick ) as well as perhaps 4 courses of brick in the room being opened and perhaps another 3 or 4 courses between the ceiling and floor of the upstairs room.
What I'm interested to know is the technical specs of the lintel required. The lintel will ideally be of concrete construction so that I can render after.
Thanks for any wisdom this forum can share.
twoblues