Wall heights are only valid when the stone is laid up with Type S mortar.
We recommend that ALL walls have horizontal reinforcing such as a ladder type by Dur-O-Wal, Inc. The reinforcing should be at a minimum of every other course and out-to-out size should be 2″less than the wall thickness.
Expansion joints should be at a maximum of 40 feet on center. These joints should be filled with sealant. The expansion joint should also follow through the concrete foundation.
If a thinner wall is desirable, columns and/or pilasters are necessary. The columns would form approximately 2 foot squares and be filled with mortar. They would also require vertical steel reinforcing extending from the foundation.
Use of thinner stone may not result in appreciable cost savings. For example, a 6″ thick wall that is 6 feet tall would need columns at about 15 feet on center. Column spacing any larger than this requires excessive steel reinforcing in the wall.