Age starts it, but more speeds it up
Mortar is made to wear. Lime mortar is the soft part of the wall by design. It wears down bit by bit over the years. That keeps brick safe. Crumbling after 40 or 50 years is normal.
Some walls fail in 15 years. Then more is at work.
Four things that speed it up
Water that sits. Joints that stay wet turn weak. Bad gutters and poor grade keep walls damp.
Frost. Water grows as it freezes. In a wet joint it pries mortar apart, over and over each winter.
Salt. Salt forms crystals in the pores. The crystals push mortar apart. White crust on brick is the first sign.
Wrong mortar. Hard cement on joints made for lime does not flex. It cracks and lets water hide behind it. Harm shows up late.
How to stop the cycle
Fix water first. Clean gutters. Shape grade away from walls. Then repoint with mortar made for your brick. New joints last when the cause is fixed.
Questions about your brick? Call (301) 679-9193 or send the form. Estimates are free.