There really is no exact science to determine the value of an apartment with a terrace, balcony or an outdoor space. So how do you determine the value of one property to the other? Well...after some reacearch I have come up with a general concensus of what the majority of the agents and brokers use in NYC. Outdoor space tipically carries a value of 33% to 50% of what the interior price per square foot is. A new full service luxury building should be valued at the 50% mark and the older buildings with no doorman and lacking on the ammenities should be valued at the 33% mark.

Example:

Condo A @50%
1000 interior Sq Ft
500 Sq Ft Outdoor space
Price per square foot 1500

Interior Value $1,500,000
Outdoor Space Value $375,000
Total Value $1,875,000