As printing costs continue to fall it will become more economic to 3D print larger and larger models. I have several designs prepared that the technology is just not ready for yet. Here though are some smaller things that can save you a lot of modeling time and virtually just need painting before placing on your layout.
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Outdoor privy to place in rear yards of terraced houses. Roof and door are detached to allow easy access for painting. Cover walls with brick paper or paint walls to simulate a stucco finish. The toilet cistern is printed with a slight clearance from the back wall to allow you to slide a piece of brick paper in to cover the wall without triming around the cistern and pipework.