The mixing ratio of stucco is to use at least 3 cubic feet of plaster per bag of cement for the scratch coat and a maximum of 5 cubic feet per bag of cement for the brown coat. Water is added to the mixture as needed.
The scratch coat is added first and is the thickest of the coats, normally around 1/2 inch. The brown coat is then added, building the thickness to 3/4 inch. The last coat of stucco applied is the finish coat, manufactured stucco, which is premixed and requires only water. The three layers require a minimum thickness of 7/8 inch over frame construction.