How do you create a house with the outside and inside? Obviously we use a 3d program to design it like maya, 3ds etc but do we create it as 1 object with many texture selections or do you split it into parts? im going to add props like beds desks etc separate but the question is to do with the outside and inside of a house with window sills, gutters, drain pipes inner walls, outer walls etc? any info on the best approach will be greatly appreciated cheers.
There is no definitive answer. A lot this depends on what works best for you and your level design for your game.
A modular approach is typically preferred for game engines. You can build the entire house exterior/interior walls as a single model with multiple materials and that will work as well. You will not be able to cull any objects that are not visible on screen since the entirety of the mesh needs to be loaded in the single mesh instance. This can potentially be a performance hindrance if you’ve got a lot of materials or complex geometry.
I hope this helps! 
Tim
This tutorial on Eat3d helped me a lot when I wanted to learn about modular modeling for games
thanks guys much appreciated… ill check the link too great stuff