I've basically talked my husband into one of these. But it won't be until maybe spring of next year. I agree with the bigger the better! :)

I agree with ragamuffin, make it as big as you can afford. My old sewing room was 20x20 and whereas it was "packed", I no longer make clothes, and I don't have the other hobbies that you do, but I can just about guarantee you that 14x18 won't be big enough, although it MIGHT be, at first, then you'll just outgrow it quickly.

It all depends on what all you plan to have in your room. My room is about 20 x 40 and could be larger. There is a stairway and bathroom out of that as well. I have a hide-a-bed, recliner, entertainment center, bookcases, large table for scrapbooking, built in drawers along the stairway wall and under the west window where there is a kitchen sized sink. I also have an island for cutting with storage underneath. So, like others have said - make it as big as you can afford :)

You will need a very large yard for a great big room. Can you get permits and approval for it. Lots of practical things to think about. I would talk to planning and zoning before I got too deep into it. Do you have sewers or will you need a septic system or have it upgraded? I hate to be practical but, very important to look at these things.
I down size my stuff all the time. We are not doing anymore building and must live in our present space.

As big as you can afford without going into debt. And if at all possible, a powder room in case it's raining, snowing, freezing, hot as blue blazes and too far to walk to the potty all the time... :o

I live in the middle of 10 acres, and have a pad all ready to go, the proposed building is close to the current power pole and about 20 feet from our 2nd well and about 50 feet from the septic tank.. I have talked to the planning commission and when I get the plans finalized they will help me with the permits, we are doing this the right way, we don't want our neighbors complaining. By the way, our house is on a hill that know one can see from other houses or the road

I would make it at least 20' X 20'. Mine is to small.

I'd build as big as I could afford and the law will allow..... It will "grow small" real fast.. lol

It's fun to dream. I've outgrown mine. I'm trying to figure out how to make the area more workspace and less storage. Building another building is out of the question due to $.
We are enclosing an area of the garage for LAQ machine and I think I can put storage in there. I don't want to keep expanding, so maybe that'll be enough.