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My boss in Phoenix told me to use a 3/8 inch joint on a big garden wall and it looked wrong from day one.
He said it would save time and mortar, but after the first freeze-thaw cycle, the whole 40-foot section had hairline cracks in every single joint, proving my gut feeling about needing a half-inch bed was right all along.
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sarah_hart6d agoMost Upvoted
A three-eighths joint on a big wall in a freeze-thaw area is asking for trouble. That thin mortar bed just can't handle the expansion and contraction. I've seen it happen on a patio border, smaller than your wall, and it still spiderwebbed after one winter. The time saved on the front end gets eaten up fixing cracks later.
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sullivan.spencer6d ago
My uncle's been laying brick in Chicago for thirty years and he swears by a 3/8 joint for garden walls. He says a half-inch bed holds too much moisture and actually makes spalling worse when it freezes. That thinner joint cures harder and faster, which can handle the stress better if the mix is right. I've seen his work from ten years back and it's still solid with no cracks. Sometimes the problem isn't the joint size, it's the mortar mix or how wet the blocks were when they were laid.
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riley_miller256d ago
That exact thing happened to me on a long walkway in Denver. I got talked into thinner joints to cut costs, and the repair call the next spring was not a fun conversation. Now I insist on a full half-inch bed for any exterior work in a freeze zone, no exceptions. The extra mortar is cheap compared to redoing the work. It holds up so much better over time.
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