INSTALLATION — Printable Version INSTALLATION Laying Masonry Walls All PRAIRIE stone units shall include W.R. Grace DRY-BLOCK® water-repellent mortar additive added to each batch in the appropriate dosage rates for mortar type N or O (Type S mortar is too strong and will create hairline shrinkage cracks) per the manufacturer’s instructions. W.R. Grace DRY-BLOCK increases bond strength and completes the water repellent wall system. Use 4” horizontal joint reinforcing wire installed every 16” O.C. When using 12” or 16” high PRAIRIE stone units, install every course. This will significantly reduce or eliminate the shrinkage or movement of hairline cracks. Control Joints: Control joints should be no more than 20’ apart. It does not have to continue through the block. Control joints should be located 4’ to 6’ from corners. Control joints must be included at all inside corners, especially at wall piers, as well as at the corner or side of any large opening or window. Northfield Block Company will review PRAIRIE stone project specifics for placement recommendations. Rake and Caulk: Rake and caulk all windowsill head joints and coping units.