cement board panels as siding

[Apson]

I'm thinking about building the Little House plan with the flat roof and I want it to have a really modern look.  I've been researching exterior cement board installation PDFs from various manufacturers and can't seem to settle on an installation system for something like HardieBacker 500 as an exterior siding (i.e. flat panels with no lapping).  Nichiha USA has a high dollar system where a specially ribbed strip of EPDM is used as flashing behind the joints.  This got me thinking I might be able to actually glue the cement panels into place using pre-mounted strips of my own EPDM flashing before I fasten the boards...sort of like doing an EPDM roof but sticking the "roof" to the rubber (and then putting screws through it, aye).  I'm also wondering why I can't simply attach the cement boards right over properly installed Tyvek (or similar) with very nice uniform 3/16" spaced joints and carefully caulk them before painting.  Just looking for some additional ideas.  I'm PDFed out for now.

Thanks!
Aaron

Here's the appearance I'm after:

[Apson]

After some more research I think this might be a rainscreen system.  Some of the joints appear caulked, though.

[glenn kangiser]

The backer board is not very pretty... mostly kind of porous for sticking tile to it.

I think you may want the stucco look with expansion joints in it sand it would be a lot cheaper too.

Just think of it ... you could also gain some new stucco skills...      

http://toolbelt.buildiq.com/topics/exterior-finishes/stucco-3-coat.aspx