Thank you miamijaguey, cow-boy and fenix. I think cow-boy's answer is probably the correct one. So sin distribuir means without a fixed plan?
Yes, thank you so much for that explanation. This article is from Spain, perhaps sin distribuir is more commonly used there.Sin distribuir, is not a common way to describe in Spanish a floor plan in which partitions (or walls if you wish) between the different spaces (bedrooms, living rooms, etc) are yet to be laid out. It is so, because the final lay out is left to be determined by potential buyers or occupants.
In this particular case, to my understanding, sin distribuir refers to the fact that it is yet to be determined where internal partitions will go to divide spaces.
The word we use mostly in Argentina is 'planta libre'. It means the floor plan is 'free' to be divided with all the internal partitions the pontential buyer or occupant wishes to.
HOpe is more clear now.