^ use the insert edge loop tool to get more geometry, those 2 edges is the first step to a chimney, in this case.



^ for interior use the insert edge loop tool, delete one face, replace it with a door or something and use the camera to move around inside the house to add objects. Floors are usually pretty easy to create, usually a texture on the floor faces will create a nice floor.


hope that helped you a litle atleast. when i was a noobie i loved making those houses. and remember, always go from low-polygon to high-poly. more details on your house requires more polygons, the most useful tools would be extrude, scale and move, merge vertexes and insert edge-loop tool