"Mortar should never be stronger than the bricks" is a well-known maxim in the bricklaying world. In this context, "stronger" does not mean its load-bearing capacity, but the mortar's hardness and permeability. Hard, dense mortar should not be used to surround porous, open-textured bricks.

Is mortar stronger than brick?

While it is commonly thought that a strong mortar works best, the opposite is actually true. When the mortar is stronger than the brick, the wall is susceptible to water damage and its durability over time is reduced. ... Walls in many historic homes were constructed with coal-fired clay bricks and lime mortar.

What happens if mortar is too strong?

What Happens if the Mix is Too Strong? Too strong a mix, i.e made with too much cement and your mortar may dry too quickly, shrink and crack. Cracking can be avoided by reducing the amount of cement in the mixture and ensuring the mortar is wet enough.