A 20-foot chimney stack in Detroit taught me to never trust old mortar without a test patch

We were repointing a century-old factory chimney last spring and the original lime mortar just crumbled away like sand when we started. I had to stop the whole crew, mix a small test batch with a 3:1 sand to lime ratio, and let it cure for two days on a spare brick before we went any higher. Has anyone else had to completely halt a job to figure out the right mix for historic brickwork?

2 comments

2 Comments

jade24010d ago

Had that happen on a brownstone last year. We ended up using a super soft 4:1 mix with hydrated lime and it bonded perfectly. Saved us from a total blowout.

ben13810d ago

Interesting approach @jade240, but in my experience that mix can fail on older brick if the substrate isn't just right.