Dear Jure,
- I do not know if OSB is good or not: for this reason I should not use it in my house. (There are thousands of sbb without any OSB...)
- I think that a good plaster should have no cracks. If it has cracks it is not a good protection for your walls. Many factors influence cracks presence: wrong proportions in the mix, bad mixing, not precise plaster application, inaccurate bales compression, or structural problems. Generalizing is not very professional.
After reading a few books and done two courses I had the presumption to be able to do everything myself and I started building my house.
Now, after have been trained by Barbara Jones and Bee Rowan and having worked on over 25 sb buildings, I teach strawbale diy. But if you want a high quality building, I suggest to rely on a professional who has knowledge, both for design and the building process in order to avoid very expensive mistakes (and I can assure you from personal experience on my house, that are very expensive and energy demanding !!!).
If you want to save money, you can run courses and work with volunteers, but always under the guidance of an expert, but never try to save money on the design and the structural assembly.
If you want to understand better what do I mean on expensive mistakes, I invite you to come and see my house that I think is the building with the highest concentration of mistakes :-).
A good example of how not to do, very usefull in my teaching !
Best wishes
Stefano Soldati
tel. +39 335 5634287
www.laboa.org
facebook: La Boa Strawbale House