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I finally figured out why my mortar was cracking on that big wall in July | Bricklayers - Chatter Central

I finally figured out why my mortar was cracking on that big wall in July

Last month I was building a big garden wall for a job in Cedar Rapids, and after three days of work, I started seeing hairline cracks in the joints. I was using my usual mix, but the heat was crazy, over 90 degrees every day. The mortar was drying way too fast before it could set right. I talked to an old timer at the supply yard, and he told me to dampen the bricks before laying them and cover the wall with wet burlap at the end of the day. I tried it, and it worked. The next section set perfectly. Has anyone else had to change their whole summer routine because of the weather like that?

3 comments

3 Comments

mason.brian7mo ago

Yeah, that summer heat is brutal on mortar. Keeping everything damp is the only way to slow down the cure. The old timer's advice is solid gold.

hayden_nelson857mo ago

Remember the old guys used to soak burlap sacks and drape them right over fresh brickwork. Saw a crew once using a fine mist sprayer on a timer, set to go off every twenty minutes during peak afternoon heat. That extra moisture not only slows the cure but actually makes the final bond stronger by preventing tiny cracks from forming too fast. It's one of those simple things that separates a job that lasts from one that needs repairs in a few years.

daniel_wood7mo ago

That bit about the mist sprayer making the bond stronger... I'm not so sure about that. @hayden_nelson85 is right about keeping things damp, but adding water on top after the mortar is placed can actually wash out the cement from the mix. You're just left with weak sand. The real trick is pre-wetting the bricks and blocks themselves, like the old timer said. That way the dry material doesn't suck the moisture out of the mortar too fast. The burlap works because it shades the work and holds in the moisture that's already there.