Actually when you're quite far away, you see stripes because the 3D rendering engine has problem to choose whether it should display the ground or the grass of the rooms drawn on the ground. To avoid this problem, I programmed an algorithm that cuts out the rooms in the ground to display only the rooms at that place. Unfortunately, this part of the program is sometimes buggy under Mac OS X with Java 6 but not with Java 7/8.
As I'll probably deliver Sweet Home 3D with Java 8 under Mac OS X in a coming version, this might still happen only for the users under Mac OS X 10.6 and previous versions. Moving the rooms points might sometimes fix the issue though.