Am I the only one who thinks lime mortar gets too much praise these days?

I went to a historic house tour last month in Charleston and watched a restoration crew using a pure lime mix on a 150 year old chimney. Everyone there was acting like it was the only way to go. But I've been laying brick for 35 years and I've seen lime mortar fail in wet climates time and again. It crumbles too fast when you get freeze-thaw cycles. I'm not saying modern Portland cement is perfect, but I think we've swung too far the other direction. Anyone else seeing this in their area?

2 comments

2 Comments

emma_ramirez21h ago

Laying brick for 35 years and I've seen lime mortar fail in wet climates" - this hits home. I bartend in a dive bar in Portland and we've had a brick wall in the back that was repointed with lime mix twice in the last 8 years. Both times it started crumbling after the second wet winter. The purists online swear by it but they don't live in places where it rains 9 months out of the year and freezes solid for a week. I've seen what a good modern blend with a little Portland can do on an old building here, holds up way better through the freeze-thaw cycle. Not saying go full Portland on a historic structure, but there's a middle ground that actually works in this climate.

the_ben20h ago

@emma_ramirez I gotta push back a little here lol. The issue with that Portland blend is you're basically trapping moisture in the wall long term. That crumbly lime you see after two winters? That's the system working exactly as designed. The lime is sacrificing itself so the brick stays dry and can breathe. When you lock it in with Portland, the moisture has nowhere to go except into the brick itself, and after enough freeze thaw cycles you get spalling bricks that cost way more to replace than patching some mortar. I've seen a hundred year old building in Seattle that was all lime and never touched versus a 20 year old repoint done with a modern mix that started failing in five years because the water couldn't escape. The freeze thaw stress you're seeing is real, but stiffening the mortar isn't the answer. it just moves the damage to something harder to fix.