[Healeys] Garage Design

[Awgertoo at aol.com]

I am doing preliminary design of a garage and have a question for  the 
smart guys here:

The building will be of frame construction and will  be 25' wide. I would 
like to put a loft with a plywood deck over a portion of  the main floor--the 
dimensions of the loft being 25' square. The loft would be  used for light 
storage with weight being exclusively on the sides and no  appreciable 
weight in the center. I could tolerate some floor bounce if need be.  

Here's the question: What size floor joists or fabricated wood trusses  
would I need to adequately support the loft without any columns to the concrete 
 floor below--in other words using a free span--and on what centers would 
they  need to be? 

I have read from one site that 16" floor trusses on 24"  centers will span 
27-1/2'. Any input  appreciated.