Cob: natural remodel

[Ted Schluenderfritz]

Hello,
I ended up buying a 90  year old house and I would like to fix up the 
finished attic space. It's got some sort of wall board that was painted 
with a lead based paint (full of holes and peeling wallpaper on top of the 
lead paint). Would it be possible to cob/plaster or light-straw-clay over 
the walls to provide some additional insulation and to protect my family 
from the lead. would this be too heavy for the floor?

what about the ceiling which has the same wallboard type material on it (I 
believe the previous occupant used drywall tape/compound on the seams--it 
looks like a very bad job of dry-walling)

Has anyone done this on an existing structure?

Thanks for any help you can give!

Ted