Evaluate a commercial office building | Questions

[Steven Oneill]

Hi guys,

 I have a couple quick questions about  commercial office buildings

1.  What is the average % of usable space vs. rentable space 

     like restrooms,  breakrooms, hallways, staircase, elevators ect.  vs. actual space that        generates income.

2.  When you factor price per square foot,  how do you factor parking lots? 

     This space can't generate rent.  Does the price per sq. ft. change? 

     Thank You in advance.