Permit issues with roof conversion and upstairs patio

I've got an opportunity and a problem. I have unheated storage space and a bathroom in rooms within the rear of the garage, rooms that apparently have been there for many years without the county really knowing about it, at least for tax purposes. Recently, I decided that I had to change the entire garage roof, not just the shingles, but the whole rafter system with an improved design compatible with the house to which it's attached at one corner. In any case, I learned about putting a "box truss" design into the new truss system, allowing for an upstairs loft and future living space over the bathroom sometime in the future. Meanwhile, to save costs, I would just pull a permit for the roof and avoid the extra taxes for an addition, at least for right now.
However, after some consideration, I decided that I must do better than just simply installl skylights in the roof, but opted for a truss design that allows for dormers, adding more ceiling space and traditional windows that ventilate easily and view out rather than up. Then, when considering the view from the rooftop, it finally occurred to me that the view over the water behind our house is too good for just a window dormer, so now I've designed in a roof deck, filling on one side of the roof peak the "ladder" floor joist space between heavy duty trusses already required for the dormers. I don't need design help, I've figured out much of this with the truss company, but now I've got potential permit complexity and a need to rush in a deck before the rains begin this fall.
So, anybody know enough about the California county codes to know wherther I can claim the new upstairs space and dormers as simply unheated garage storage space with access to a patio? I don't mind paying for the permit, but if I add more house floor space, I'll also end up paying an additional $3,000- school tax fees. This would make the price of the addition jump a lot right now. If I can get squeak by planning with storage space though, I can retrofit the living space later. I like to budget and build slowly enough so that I can pay for them out of pocket. We don't need the living space, really, but the project would raise the value of our waterfront property value significantly in the long run.
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