The original philosophy of grouting walls developed as architecture moved away from bearing wall toward curtain wall design. It incorrectly assumed that a thin wall, lightly loaded, would act similarly to a heavily loaded thick one.
ILI believes that the structural capacity of grouted walls which are otherwise unreinforced is not well understood and that the only purpose served by grouting cavities is to stiffen the wall. Grouting causes the inner and outer wall to act in concert. Cavity wall construction assumes that the outer wall and the backup will move differently, at least between columns and floors, or within an area defined by relief angles and control joints.
Differential movement aside, grouted cavity walls cannot handle internal moisture nearly as well as standard cavity construction. Further, if the cavity is grouted full, and the stone is not dampproofed, the probability of the occurrence of alkali stain is greatly increased.
Unless there is a clearly understood engineering reason for grouting a cavity wall such as a seismic requirement or other structural considerations, the ILI does not recommend this practice. In cases where it is determined that grouting must occur, dampproofing must be applied.
ILI will, upon request, comment further on this subject.