Well, first of all one doesn't need to have a raised platform, a yurt can certainly sit directly on the ground, either on wood, or cement platform, or even some of the new designs have a tent like floor. But in tropical climate, as well as many other climates, it's best to build the platform up.
There are several reasons behind to build up, better and more air circulation (not only for heat control but also to help control moisture), less bugs (especially centipedes!), room for storage or a first floor underneath (in our case we want to frame in a small lockable storage shed underneath which will take up less build able sq footage on our small lot), better possible view (depending upon which lot we get), easier access to plumbing and other issues underneath, hmmm what positives am I forgetting.
A couple negatives that I can see is that it will be more expensive, heck if we're building up then we want a large deck to live outdoors on, have an outdoor BBQ area and to put our little Ohana on (a tent with cushy mattress for guests :-) Also, more maintenance of the platform and deck with regular treating and finishing. We would most likely only have stairs, does this matter to us at age 45, we keep the yurt to old age, will we have handicap friends come to visit, who knows at this point, but I can see keeping the height within reason for a possible ramp - ya neva know! I'm sure we will have to pay someone to do the platform and deck (which will be all in one) as we do have family and friends that have the skills, but the logistics of getting them out there during the time we need it done - not likely.
Just how high up off the ground, well that takes some consideration. One thing I'm thinking is that I would like it to be easy enough to access underneath without crawling. Thomas' knees are bad and it's hard for him to crawl to work on stuff underneath, so the idea of a "crawl space" is out. Also, I don't want it so low, small and cozy that it encourages rodents, pigs and other feral animals - especially cats! Just ends up being a gross mess! So, I'm thinking I'd like it at least 4 ft up, not sure however, I'm open to suggestions.
All good things to ponder......
A brief article written by Delia Montgomery regarding yurt platform design can be found at http://feelgoodstyle.com/2009/09/26/yurt-living-platform-design-options/
And... that's where I lifted the pic from as well (thanks Delia!)
And further, is it too much to ask that one could edit the spacing properly on this damn blog website!!