Wood Stair Treads Set in Mortar
What kind of staircase are you talking about?
What are you trying to do?
Are you replacing treads in an interior staircase?
Open or closed stringers?
Are you placing new treads over the old treads?
For the life of me, I can't figure how you would use a mortar bed in any scenario of a wood staircase.
And the only scenario with wood shims is with an open stringer staircase.
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
B. Franklin 1759