I've created a couple of roofscape models using Progecad, which is very similar to Autocad.

The buildings are all 3D solids, and the roofs are made with 3d faces. The STL print looks good to me, and I've had one model successfully printed by 3D Hubs. But when I tried to get a further print, they said there were too many technical issues.

A second model employs 3d faces more extensively for the landscaping, and now I get a similar response from CraftCloud.
...

Hi Yoana, I can't speak for any dedicated 3D printing programs - in the short time I've been printing, Cura has been the software I've used for printing\slicing though, for modelling I have quite a bit of experience with AutoCAD, pricey as it is there are cheaper alternatives one being ProgeCAD which is a fraction of the cost of AutoCAD but works exactly the same if not better!!!

What problems are you having with CAD?

thanks, there are several I didn't know..

you also missed some :
Cubify Invent / Design / Sculpt > http://cubify.com/Products/Software
ZW3D > http://www.zwsoft.com/zw3d/
IronCAD
VariCAD
ViaCAD
PTC Creo
PTC Creo Elements/Direct Modeling Express
BricsCAD
HyCAD
Cobalt / Argon
ProgeCAD
CAD Schroer MEDUSA4 Personal

and forgetting several others...

ffred