The stresses in masonry constructed of natural stone due to axial loads shall not exceed those set out in Table XXIV for the kind of stone, type of walling an class of mortar set out in that Table:

Provided that, if class A mortar is used, such stresses may be increased to 10 per centum of the crushing strength of the stone proposed to be used, as measured on representative samples, to the satisfaction of the local authority.

TABLE XXIV
AXIAL STRESSES PERMITTED IN NATURAL STONE WALLS