I haven't gotten there yet, but I plan on making a sort of masonry heater for my portable 20' yurt. First I need to finish my
and layering and get my platform moved and seal everything up though. I have a cheap adjustable 25k btu/hr propane heater in the mean time to test how much
power I actually need--yurts can work _very_ differently from traditional homes in terms of heating, throwing off estimates. My cost estimate so far is ~$2k for a masonry heater with design by professionals/construction by myself, for what it's worth.
There's a good number of ways to build masonry heaters (varies by country/region of origin, air movement principles)--the RMH are tempting for their DIY nature and typical lack of engineering. But if you keep a sharp ear on what people say during builds, they require a good bit of tuning to get working just right & efficiently. Partnering with someone knowledgeable about them & air flow dynamics, and hopefully local, would probably be a good idea.
Like Jafo says, make sure your foundation/platform can take it--with a basic heat lose estimate, you can fairly easily estimate the required thermal mass based on frequency and wood mass of burns. Standard wood decks should hold 40 psf live load--a 5' square could hold 1000 lbs by that standard. A ballpark weight is probably 1000-5000 lbs for a small/medium homemade heater.
A note on
: 2x4's have an r-value of ~4, windows from 1-4. Insulation gets cut out for electrical boxes, pipes, etc. Plus nails (metal is a good conductor) and imperfect installation. So you're actual total r-value of the whole wall assembly is not that of the insulation (although it can be close). A yurt doesn't have this problem--it uses a layer of insulation with no interruptions from studs or nails or framing. Mind you, the materials are also usually thinner (except when the mongolians use 5 layers of 1" thick felt during winter...). Yurts also have negligible thermal mass compared to most other construction techniques.
Hopefully Steve will have some experience/info to add.
What are you making your platform out of? Are you building or buying your yurt? How do you plan to insulate it?
Hope that helps a bit.