Building Envelope Grasshoper

Hi, I am new to Grasshopper so this might sound like a stupid question, How can i form one single surface on grasshopper from multiples curves?
I made the surfaces one by one with sweep2 / loft on grasshopper, but I cant seem to join them as one, or when I tried to extrude them to add thickness, its only going to one direction (x, y or z)
is there any way that I can do this in grasshopper? The idea is to create one surface the building envelopes that wrapping all of the slabs.
Hope it makes sense! Thank you :slight_smile: ![Syifa-8|690x386]