You would need to make sure the surfaces create an fully enclosed "volume"....then using the "Stitch" command should make it a solid model.
Design Manager Streetscape Limited
Solid Edge ST9 [MP5] Classic [x2 seats]
It has been a while since I did this, but I think once all the surfaces have been stitched together to make a "water tight" volume, Solid Edge will ask if you want to make it a solid feature.
There are also methods of using Boolean and Thicken to create solids from surfaces.