[Cob] wall thickness on 2story load bearing

[Michael Pruett]

The Hollies answered my inquirey regarding the width of the load bearing walls in a two-story house. ...

The walls are 3 feet thick! All are loadbearing. There is some timberframing where the grenhouse glass goes in the front. And they used joists which set into the cob and rest on a 4 by 2 wall plate. 

What is a wall plate? Since the joists are in the cob, that means the upper story cob is also 3 feet?

reference link: http://homepage.eircom.net/~thehollies/pages/plans.html

jill