convert brep model to extrude model

hello,
is possible convert a brep model to a extrudable model with a main section and a depth?
for example a column or a beam have a section(the main face) , extrude direction ,and the extrude depth .

How i find the section that it must be extruded from all surface of brep?
I think that can be a face normal problem but i don't clear understand.
thanks.

help , books , document or a simple explaination.

thanks