Pro tip: Stop using premix mortar for load bearing walls

I compared premix against field mixed Type S on a retaining wall job last month in Phoenix. The premix cracked in 4 spots after a week while the field mix held solid through a 110 degree day. Premix is fine for little garden walls but anything over 4 feet high needs the real stuff. The sand to cement ratio in the bag just doesn't cut it for heavy load. Anyone else had premix fail on them like that?

3 comments

3 Comments

dakotab9324d ago

Also something people don't think about with premix - the weather when you're actually mixing it matters way more than they tell you. I've seen guys in Phoenix on a 110 degree day try to mix premix and it's basically set before they even get it in the wall. The water evaporates that fast. Meanwhile field mix you can adjust the water on the fly, keep it wet enough to work with. Temperature swings mess with premix too, not just heat. We had a cold snap last winter where premix just crumbled because it never cured right, but the stuff we mixed ourselves held up fine. It's not just the sand to cement ratio, it's the whole curing window you lose with premix.

mark43624d agoMost Upvoted

You ever notice how premix just picks the worst time to betray you, @dakotab93? It's like it knows when you're in a rush or the weather's already kicking your butt... I swear I've seen guys mixing that stuff on a scorcher and it's more like making concrete cookies than mortar. And the cold snap thing too, yeah, I've had premix just flake apart on me like bad drywall mud. Field mix you can at least baby it along, but premix just gives up and leaves you hanging.

taylorshah24d agoMost Upvoted

Dakota hit the nail on the head there. My buddy tried to pour a patio with premix last August and it was like trying to spread peanut butter in a microwave, set up before he even got half the forms filled. Field mix you can just throw a tarp over the pile and add a splash more water if the sun’s beating down hard, no panic.