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Saw a wall I pointed up 10 years ago and changed my mind about lime mortar
I drove past a job I did in 2014 near downtown Portland last week, a brick retaining wall for a church. I had used a standard Portland cement mix back then because I thought it was stronger, and the brick faces are spalling off all along the top course. Now I finally get why the old timers push lime mortar for historic work, it lets the wall breathe and the bricks stay solid. Anyone else have an early job that made you rethink your whole approach?
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johnson.river3mo ago
Wait didn't you mean the mortar being harder than the brick is the real problem though?
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sammartinez3mo ago
Yeah that spalling is exactly what happens when you trap moisture in old soft brick with hard mortar. The brick ends up being the weak point instead of the mortar joint, pretty much the opposite of what you want.
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young.thomas3mo ago
So does that mean you'd basically have to repoint the whole wall with a softer mix if you ever want to stop the spalling, or is there a way to seal the brick to buy some time? Seems like most people just slap on a latex paint and hope for the best. Genuinely curious if there's a middle ground that doesn't involve tearing everything apart.
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morganmartinez3mo ago
@sammartinez nailed it. I had a 1920s house that was pointed with type S mortar before I bought it. The bricks were basically turning into powder every freeze-thaw cycle. I ended up spending a full summer grinding out all the old hard mortar and replacing it with a type N lime mix. Still have to repoint a small section every year, but the spalling stopped completely. That latex paint bandaid just traps more moisture behind the brick and makes everything worse.
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