Misuse of stilt car parking

Hi, We bought a flat in an apartment with 6 flats. Five flats were sold and 1 is still not sold. The 5 flats were handed over to the owners 2 months back and we shifted in immediately. But till now we are the only residents and other 5 flats are still vacant. And all the stilt parking slots are designated with one slot designated for each flat. NOw the problem is that...the builder has started building a new building a few streets away and is using the car park of the unsold flat for storing cement bags, tiles etc that are meant for the new building (which he has just started and will take another year to complete). When asked he says that since the flat is not sold he can keep his things in the parking space of that flat. It is spoiling the look and feel of the new apartments. Besides every now and then the builder sends some workers to sleep in the stilt area of the apartment at nights which compromises the security of the residents. Now the question is....since the flat is not sold can he do whatever he wants with the related parking space considering that as per supreme court ruling the stilt car park comes under common areas (as far as I remember...not too sure). And besides can a car park be used for purposes other than for parking vehicles. Can the builder use his position and do whatever he feels in the unsold premises especially in the stilt parking slot. Experts...Please let me know....it is becoming a big nuisance as the people keep coming to either take some items or store some items in the parking slot and is spoiling the look and feel of the entire premises.