Look, I don't want to get side-tracked in dissecting one site. That's not the only source I'm looking at ... and that same site has actual house plans for stuff too large to put on wheels.
I thought I was pretty clear when I said the homes I was discussing were asserted to meet building codes - not HUD rules, trailer rules, camper rules, or any other sort of rules. To attempt to apply the NEC, or other building codes to something that was outside their scope would be a meaningless discussion.
The small homes bring up many other issues ... for example, the tiny, nearly counterless kitchens often also have the laundry equipment- which can open an entire discussion about SABC's. That's what this is, though - another discussion, perhaps for another thread.
Look at that site's plans for the larger homes, and you'll see that the use of lofts as sleeping areas is not limited to the trailers alone. Alternatively, some designs have raised platforms in cupboards as the place to stick a mattress (cupboard dimentions match standard mattress sizes, with no open space), or a similarly tight 'bump out'. The author is quite open in stating that his sleeping areas often do not qualify as 'habitable rooms' under the building code. In several instances, only the central portion of the sleeping area is 'habitable,' with the margins also in use. So, there, in effect, we have a 'habitable' area without either walls or a floor - quite a feat!
I will admit that I am in no position to evaluate the authors' assertions that their various schemes 'meet code.' I have neither the information nor the competence to make that call. I also note that none of these various designers make any claim to being architects, or having any professional expertise at all- so their assertions may be in error.
Architects are forever designing things in a manner that seems intended to confound codes. Perhaps that's the best reason for codes to stay out of the 'design' business.
