I originally started this post as a reply to the comments regarding the post below, but it got a little long winded so it now gets it's on spot on the front page.
Castle interiors were whitewashed, and were often painted with decorations to boot! Thanks for the reminder though, the structure would definitely be partly stone and partly "finished" interior.
You know, I've been to the Castlemagic site several times drooling over the really nice work that they do, and as I've advanced my construction knowledge I haven't stopped back by to look at the work going on in the pictures. Thanks for making me look again!
From what I can see, Castlemagic does a masonry stone wall, on the inside and outside, only one layer thick. In between the two there is a fairly large gap on the order of 8-12" that has re-bar and foam insulation in it. Once the masonry walls are set up, concrete is poured around the insulation to fill the gap. The stones are probably brought in, they border on quarry cut ashlar variety. They are very consistent as far as thickness and quality. This means they are very expensive but guarantees a good, consistent finished product. Looks good, works great. One could buy a mason's stonebreaker, hand pumped [image here], powered by air [image here] and fully powered hydraulic [here]. The first two are under $2000, the last is over $30,000. If one was willing to take the time to split stones, a very nice finish could be achieved. For $30,000 one could probably buy all the pre-split stones one would need for a reasonably sized building.
My issues are that I don't have the knowledge yet to appropriately design a masonry/cement wall for the height of the structure I'd like to build. I may very well be way out of line on my estimates for the structure I've been looking at because of that lack of knowledge. Also, the amount of concrete fill Castlemagic uses looks to be very large, ergo expensive. I'd like to minimize additional costs.
Here's a thought; why not use the slipform method or the method mentioned in the aforementioned book and build in a re-bar and insulation core?
A quick search of the internet reveals a really nice flash presentation of a pretty house done with slipform: House of Stone There are several sites that build using foam cores and a reinforced stone fascia, Hollowtop is a green building site that features this method in many places.
Overall, these methods seem to require more cement, but the build times are shorter and there's less stone to haul. I'll really have to work at finding out what type, quantity, strength and design of materials will be required to build something. Guess it all boils down to how much money is in the bank or how willing one is to haul lots of stone when it's time to build!