Yet another weird question from the architecture student...

I've lofted some curves together, with the loft tool set to triangular polygons. Now I'm trying to give those planes thickness. I assume that it would involve some kind of extrude command, but I can't figure it out for the life of me. The only info I could find was for extruding individual faces, and since the geometry i fairly complex, that would be annoying. It's also problematic since I plan on building this thing on an RP machine and I need nice smooth planes, no weird gaps between extruded faces.

I will be very, very grateful to whoever solves the plane thickening mystery, it's driving me crazy!