I sometime get this question asked by building board members and clients. My answer to this question is “It depends!”. However generally speaking I do think that adding more storage space is a no brainer because New Yorkers never have enough storage and the rental or sale of storage units generate income to the building.
A play room could add value if the subject building has many couples with small children in the two to ten age range. It is hard to gauge the amount of value a playroom would add to the value of an individual apartment. Also keep in mind that as the children get older they will outgrow their need for a play room.
There is a condo in the east 80’s where I have sold many apartments. It was built in the late 1980’s. This building is very popular with young families because the layouts are very generous, and they get very good light, and many have views. This may shock you, but they have no storage units in the basement at all! They do have a very nice gym and an outdoor playground for the children.
If your building is considering adding a playroom in the basement it may be a turnoff to parents because of there is no natural light.
Check to see if the basement is free of mold, leaks and pests such as water bugs that enter through plumbing lines, drains, and vents. So, make sure these are capped and screened. Also, mice can be a problem so make sure that there are no problems with them gaining access. In addition, be aware how store items and what you store in the unit. Also, before considering adding storage units it would be a good idea that there be the same number of storage units as the number of apartments if possible.
At the end of the day I believe that adding more storage units generally adds more value than a play room in your building. However, if there is adequate space to add a well fitted out gym then that could add more value to the building than adding more storage units because a gym would be used by a larger pool of residents than a play room.