ABSTRACT
The strength of the mortar has less influence on the ultimate strength of a wall than might be supposed. An excessively strong mortar tends to concentrate the effects of differential movement and produce fewer and wider cracks. Weaker mortar will take up small movements and cracks will tend to show as hair cracks in the joints. Thus mortar should contain only sufficient cement to give adequate strength in the walling, unless there is good reason for a richer mix, e.g. in cold weather, when a richer mixes develops strength quickly enough to resist the effects of frost.
