Timmy2 correct the double wall is for reinforcement there is a 6" concrete base twin walls with rebar and concrete and the the slab which is also 6" with rebar. My engineer over kills everything but hey who wants to be working down there and have it collapse around you with a 911 or beetle on top....
Thanks Uwon there will be 5 double sliders looking out onto that view which is the 15th fairway of a golf course with a view of a lovely hill behind.
