GST is payable on supply of Goods and services or both.
There should be a supply for a consideration. Security Deposit is just a deposit and does not involve any supply and neither a consideration since the money will be given back after you surrender your meter.
However deposit is made by your builder and here we have to refer whether he was acting as a pure agent or not.
In this case GST is not applicable, but if builder was not acting as your agent, he has to charge GST on all expenses or payments he made on your behalf.