Kristine Walker wrote:is it possible to add cob walls inside an existing standart home or to add on a porch type room to the back made from cob?
Yes, but you'll need a structural engineer to sign off on your plans making sure you are not adding to much weight to your walls or foundation. And it's best to find one that specializes in Natural Building like these guys Precision Structural Engineering, Inc.
http://www.structure1.com/html/services.htm It is easier to do an add-on that way you can build for the cob from the foundation up, and if you do a post and beam add-on you can build under the roof.
As for the basement question -
It sounds like your going for aesthetics more than the functionality of cob - right?
So then
the answer is yes with some considerations, such as is your basement dry? No moisture issues of any kind? Crack free? Most basements are not.
Questions become - Can you seal your basement walls and floor making it dry,
water tight? You may want to consult with whom ever repaired your basement about these things.
Next, assuming you have a dry room to work with you may want to consider adding a layer of slip
straw between the cement and cob finishing for insulation, or maybe use some type of other insulation. And because you don't need the cob to be structural you can have a skinnier wall like the typical internal cob wall. The most important thing is how to attach your insulation/cob wall to the cement walls. This usually isn't covered in cob
books, as they don't go into much on remolding standard buildings. But any carpenter will be able to help you with bolting some wire or other frame work to your cement walls. This frame work would then be completely covered by the cob, holding it all in place. This is especially important if your area has any kind of tremors or seismic activity. And a cob floor would add a nice soft feel to hard
concrete, but again you want to first consider your insulation options.
There are many resources covering the details of cob, for example building with COB: a step-by-step guide.
I hope this gives you some ideas ~