Question about mortar mix ratios for old house repointing

I read on a preservation forum that houses built before 1920 need a different lime mix than modern Portland cement, but the local supplier said to just use Type N. Has anyone dealt with matching old soft brick mortar on a 1910s foundation in the northeast?

2 comments

2 Comments

ruby4944d ago

Type N will wreck old soft brick for sure.

anna_craig4d ago

Ruby494 has it right. You said "Type N will wreck old soft brick for sure" - have you actually seen it happen with your own eyes on a foundation job, or are you going by the general rule of thumb? I ask because I've run into jobs where the old brick is harder than expected, almost like a glazed face brick, and Type N actually seemed fine. But I've also had a 1920s brownstone where the mortar crumbled to powder in two years because the previous guy used a standard mix. What specific signs do you look for to tell if the brick is too soft for Portland?