Most building codes have a formula as JVO said. The footprint, or total square footage of the buildings can only use so much of a percentage of the property.
You really need to go and get a copy of the regulations so you can see for your self what their game is. Then when you think you know what you are talking about ask a lawyers advice. Find a lawyer that has been successful getting some one else's denied building application approved.
I think he was also right-on about the "permanent" structure part also. When you pour a permanent foundation for a building 2 things happen. 1) They can tell you whether or not you can do it and 2) they tax you on it. As soon as you pour footings you are screwed, tax and regulation wise. I just jumped through many hoops to get my garage started. (see thread)
http://www.garagejunkies.net/showthread.php?t=1725
They did not want to give me a variance, but I had an intelligent response for all of their concerns and issues, some of which should never have been applied to my situation. Offsets from road, etc.
When I built a 12X16 shed on my property, I found out as long as I didn't use concrete footings, it was a moveable structure, i.e. "temporary" and I could put the damn thing any where I wanted to. It's been there for 18 years!
When you apply for a variance there is usually a public notice, and your neighbors have a chance to support or complain about it. Did any of that take place?
I don't see why you couldn't build dog house type dormers off the main building and store items in there, as long as you use bluestone or patio blocks as the floor, which would be (re)movable. If you are thinking about being able to enter those storage areas from the building side, you better make sure you header it off before you do it. (if it's a load bearing wall) I would incorporate any ingress/egress points into the building where those dormers may be in the future, when I submitted my plans. Just tell them you may want several additional ways in and out of the building, but you haven't decided where they will be yet. There is a loop hole in everything, That is how politicians have been operating for years, play their game. The wording is usually ambiguous in some way, shape or form, exploit it, and have fun while you're doing it!!