Builder delayed the construction What action can be taken

We r the owners of a old bungalw.Gave it to a builder to build a multistoried aparment 4 storied under regd agreement.it was to be built by June 2016 with certain drawing 1n about 3000sqft leaving other areas as per std.But the builder failed to complete it even after repeated reminders.As per agreement after june 2016 whole building stand transferredas and where condition to owner without any share of builder.He will atleast take 6 months more as per him but doubtful.Only 3 storied bldg done instead of 4 as agreed.Rooms are much smaller than promised.What sd be done by the owner of the land