Hi Jim,

I spend a good part of my life examining timber-framed buildings where the panels (internal and external) are filled with wattle & daub. Most of these (read all) have a single skin that is about the thickness of a single brick i.e. 4.5" and certainly not 12" as suggested by others. These are not warm buildings in winter. Density would be about 80% of brick.

Cobb walls are thick however these do not contain timber-frames and are laid using shuttering and raised in lifts as the preceeding layer sets and hardens. These buildings are significantly warmer in winter.

Wattle & daub is certainly useable on external walls provided this is lime washed (multi coat) to help prevent migration of rain / damp. Originally timber-framed / wattle & daub buildings were coated in limewash (frame & infill panels). This was used to help seal up shrinkage gaps that opened up after drying in situ.

Ken