Victoria and Ilia,
I have been told that for this kind of project, in order to add a layer of plaster on a concrete wall you could go with a layer of a mixture concrete/hydraulic lime then a mixture hydraulic/ non hydraulic lime and then your regular frescoe layers.
What do you think?
I am not sure what kind of plaster you both are talking about and Victoria if you only have Home depot to do your shopping then where do you find your lime?
Myriam