Private area and common area in Apartment Complex.

I own an 3BHK apartment and a stilt car parking in a Residential complex. The schedule of property is described as " Property Unit SV48 in Block B on the 2nd Floor apartment 202 in the building measuring 137.36 sq:mt (approx) (1478 sq:ft:) of saleable area containing three bed rooms with car parking space P-6202 in the stilt contained in the complex known as "shivaranjani" to be construed on the "A" schedule property as per specification agreed. As per code of conduct of the Welfare Association, I requested them to allow me to build a temporary/or permanent wall on the outer periphery measuring one meter high and 2.5M long to prevent, splashing of dirty water pouring out of the drain tubes when washing the common area of 9 levels above, excess dirty water falling out from the potted plants kept close to the balcony rails, and pigeon droppings. The Association insists that the stilt car park area is a "common area" and no individual have the authority can not alter, modify, construct any thing in the common area. The wall I proposed does not obstruct passage of any individual as it is periphery of the car park area, half of that side is the back wall of the main staircase. ( I can send photograph of the car park). The dispute between me and the association is going on since last three years even Elder's helpline (under the Patronage of Bangalore City Police Commissioner) could not find a solution as the Association insists that the "stilt car park" is co owned and is a common area. I also pay property tax to Greater Bangalore Mahanagara Palike for the car park at a rate fixed by them since 2008.