12/21/2025
TLDR: No cement mortars should be used in repairing historic brick and stone walls
lime mortar is needed. Hot lime mortar or lime putty mortar is optimal. NHL mortars are okay. Cement mortar of any kind is detrimental.
This is not yet common knowledge among masons in the US. I hope that changes soon. Many of our historic buildings will not survive another generation of improper repairs.
One of the most damaging myths in masonry:
“Stronger is better.”
It isn’t.
Historic brick and stone were designed to be sacrificial systems.
The mortar was meant to fail first — not the masonry unit.
When we introduce overly strong modern materials, we don’t strengthen buildings.
We transfer stress into the brick and stone.
That’s how you get:
• Spalling
• Cracking
• Irreversible damage
Good masonry isn’t about power.
It’s about compatibility.
The best repairs disappear — not because they’re invisible, but because they work with the building.