In this system, the 2x6's (or whatever they end up being)
are not structural at all, also the extra wide plate does not necessarily ave to be a single timber. You could have your regular timber plate, with a 'fly' extended out attached to the top of the 2x's. The purpose of these 2x's is to support walls sheathing on the outside and drywall on the inside. The idea is inspired by a traditional infill system and is going for that appearance on the inside of the structure.

The actual load bearing structure is a timber frame, it is therefore stronger and more durable than a 2x stud frame, and you don't have to have 8" or 9" of timber on the inside for it to have the beauty of timber. Remember that infilled houses had plaster right up to the edges of the timbers, and often the timbers themselves were plastered or whitewashed over as well.

Now that said, an idea in its earliest forms is very rarely a solid idea, and it's for that reason that I have put it up here.

I have considered the idea of just having a small 2x2 framework on the inside and on the outside with the large cavity in between filled with cellulose or spray foam, But I am not so certain that the cost to the customer would be reduced as a result of using less wood. The reason I say that is because that would require considerably more labor to install, whereas a 2x stud frame between the posts would supply a framework for attaching both the outside and the inside wall coverings.

There are many old barns in my area that use a system quite similar to this, and it is where I have taken some of my inspiration. These barns are true timber frames, often with bents spaced as far as 15 foot apart. However 2x studs are framed between the posts to support the siding. This system was a very common system on old barns and houses alike. The change here is that the studs are moved out a little in my system so that the posts are insulated from the exterior air temperatures.

I have thought a lot about the plates and sills in this system. To have the plates extend full size out 3 inches is excessive, and overly large. But since the stud framework is not structural, the plates could be extended by way of boards that extend past the edges of the timber posts.

And I researched it, 1/2" drywall is can be used with 24" maximum O.C. wall studs, 3/8" must be 16". So with 1/2" drywall, which around here at least is normal for walls anyway, there is no need to provide additional support to the inside.

This system isn't going to be the perfect insulator. It's insulating performance will not be as high as SIPs, I am trying to find and/or develop another system that can do just that. This system is designed to provide an affordable alternative. It is designed for use on a smaller timber framed home, not a timber mansion, the point of which is to allow normal middle class people to have a timber frame. As I have said before, my dream is to open up the world of timber framing to people who cannot currently afford a huge SIP mansion, and who lack the drive, skill or ability to build their own.

For a more thoroughly insulated structure, at a somewhat higher cost, I would definitely prefer the double wall system, with a single large cavity between all posts. This system would provide far superior insulating properties I know, But I think at this point that the extra labor would make it quite a bit more expensive. This other system is I think a reasonable alternative. That said, I am sure that it would be possible to develop a system where the labor costs involved would not be significantly higher.

I am sorry if you got the impression that the stud framing was in any way structural, I assure you that all of the load is born by the timber frame, which the studs are then attached to solely for the purpose of supporting the walls.