Your space is probably an "exclusive right to sell". You need to check your deed and condo documents to determine whether your space is only for your unit, whether it can be sold to another unit owner in your building, or whether it has a separate deed and can be sold to the public.
MOST parking spaces in Back Bay cannot be separated from the condo. I will assume this is the set up you have.
An outside tandem parking space sold at 241 Beacon Street a couple of years ago for $80,000. Your location is further away. I would estimate the value of your space to be around $65,000 assuming you are just trying to add it to the value of what your condo is worth. I have sold several different parking spaces in the Back Bay and there are many variables. I hope this helps!
I hope this information is helpful to you.
(Choosing an answer as a best answer, or at least as a thumbs up, helps those who answer questions.)
Here are 3 spots currently on the market:
A good answer to your question depends on where your parking space is located,and whether it is a single space or a tandem space. Furthermore, the Back Bay is NOT all the same. Parking spaces vary in prices depending on the attractiveness of the location. There is a parking space right now for sale on Comm. Ave. for over 300K.
Therefore, The worth of your parking space depends on where your BB location.
I hope that helps.
Scott Beard|Bean Group