the subjects says it all.
I want to plaster a natural stone outside wall because it is not beautiful and as it is a very old house (200 years) the rain washes out the old lime/sand mix. I thought of mixing in vermiculite to make a insulating plaster .. But I can't find info on it so I'm very much in doubt if this is a good idea. Is or isn't it ?
Thanks in advance
Ciao
If you are talking about a thin layer (inch or so) plastered on the outside, then it won't make any difference to it's "insulating" properties. However, it will make it weaker.
My opinions are barely worth the paper they are written on here, but hopefully they can spark some new ideas, or at least a different train of thought
I agree with Peter. Vermiculite loosely filled has an r value of about 2. Mixed with lime/sand and applied in a pretty thick layer, you are not looking at a great increase in insulation. You are better off making a strong lime plaster that won't need to be reapplied anytime soon.
Offering my .02 cents if I may. If the rain is in fact washing out the old lime/sand mix, then applying ANY plaster is placing a bandage over a bullet wound...your wall will most certainly come crumbling down at some point. If your wall is also 200 yrs old then what you have in your favor is very likely a well built wall with Natural Hydraulic Lime that could certainly be made beautiful (and strong) again simply by repointing...you may just fall in love with it. Might I recommend a peek at www.limeworks.us , or better yet http://www.buildingconservation.com/articles/pointing/lime-pointing.htm
