posted 13 years ago
Coating burlap with portland slurry is pretty common as a way to use it as lath or formwork for ferrocrete. Extremely thin sculptural layers would be the advantage of such a system, but resilience would be the question as it relates to cob. Each cob formulation is different base on clay profile and binder type. Look up wattle and daub on u-tube and find lots of ways to coat a screen or lattice or panel with mud will pop up. My personal favorite is to use light straw claw, woven thatching style into the lattice, completed with clay or cob finish.
cob as roof works in low-rainfall, extreme desert climates. cob as an insulator under a more traditional or ferro-crete/gunnite roof would work as well. the better option is to use packed light straw clay. it is substantially lighter and easier to incorporate into a standard structure. on the current cottage i am building, i am going to embed large timbers at second floor level, purlin with medium timbers, lay used galvie tin over the boards, and make a second story cob/earthen floor. needless say the structure to do this safely is very very heavy, and the size is small. a simple, small cob roof could be made the same way, just float or embed framing into the cob, add tin, shakes, or rubber.