A 12' castle shouldn't be too hard. A little more info would help some.

Do you have a design in mind?

Can it be made of styrofoam or some such inexpensive material that can be easily worked and painted? This could be built up in layers pretty easily (like you suggested).

Does it have to be fire proofed??

What scale are you building?? Is it in the 'background' or do the folks on stage interact with it?

How wide is the set piece?

We did a castle piece for my daughters wedding. She was married in a theater on a stage. I built two 12' round towers of plywood along with two curved walls that sort of angled off towards the front and sides of the stage. They were about 8'long and sloped down towards the front too. We covered them with carved carpet underlay pieces which we painted to look like stone work. The roof tiles were also pieces of carpet underlay. I considered using foam, but he underlay proved to be easier to curl around the curved surfaces.

We gave the foam two coats of contact cement to seal it enough for our paint to look good. Unfortunately the room wasn't vented well enough where we did the painting and my father-in-law and I got kinda wasted on the fumes. It was funny at the time.

We then suspended a canvas between them on which a very fairy tale like castle was painted. A scrim they call this I believe.

Anyway with the theater lighting on it was pretty impressive.

The bridal party were all in costume (no suits and ties here) and it was FUN!

A little more info might help me give you some more pointers.

Let me know if you need more.

-dan

[ January 10, 2002: Message edited by: Dan Sawatzky ]