Traditional lime mortar vs modern cement - which one actually lasts longer?

I tried repointing an old stone wall with lime mortar on one side and Portland cement on the other three years ago, and the cement side has already cracked while the lime side is still fine, so what have you folks found holds up better over time?

2 comments

2 Comments

sarahh8111d ago

Yeah, what you found with the cement cracking after three years doesn't surprise me at all. I've seen the same thing happen on old stone buildings around here. The lime mortar just breathes and moves with the wall, but the Portland cement is too hard and brittle, so it cracks when the wall shifts or when moisture builds up behind it. I think a lot of people assume cement is stronger and will last forever, but that's not how it works with historic masonry. Lime mortar might need repointing every 50 to 100 years, but cement can fail much faster and then you're looking at bigger problems with the stone itself. Sounds like you've got proof right there on your wall which one holds up better.

river_adams2510d ago

My uncle's place in Connecticut had a foundation repointed in the late 90s with Portland cement and by 2010 the whole thing was spiderwebbed with cracks and a few stones had actually popped loose. The mason we called in said it was because the water couldn't escape, it trapped moisture behind that hard shell and then froze, expanding and pushing the stones right out of the wall. Meanwhile the lime mortar on the 1780s section of the same house was still holding firm just needing a spot repair every couple of decades. It's wild that the old guys figured this out with basically no science, just watching what worked over hundreds of years, and we still keep repeating the same mistakes because cement is cheaper up front.