Pro tip: found out the mortar mix ratio I was using was way off and it came from a 1950s Army manual
I was on a job in Gary, Indiana last week repointing a 1920s house and the homeowner handed me an old Corps of Engineers manual from 1953 his grandpa kept. The lime to sand ratio in there was 1 to 2.5 for soft historic brick, and I had been running 1 to 4 for years because that is what my old boss showed me. The manual said hard mortar on old brick is the main reason those walls spall and crack within a decade. Anybody here work mostly on pre-war masonry and have a mix they swear by?
Been mixing mortar like I'm baking a cake from a recipe my grandma lost, just vibes and whatever ratio feels right. That 1 to 4 thing is wild though, your old boss basically taught you to crumble those old bricks on purpose. The lime ratio really does matter on the soft stuff because those old bricks need to move a little and the hard mix locks them up, then the freeze thaw does the rest. Sounds like that grandpa knew what he was doing keeping that manual around. Might have to dig through some old books myself before the next repoint job.