Question about different mortar mixes for retaining walls

Put up a 40 foot retaining wall last month out by my place near Tacoma. Used type S mortar but it was a nightmare to keep from sagging on the bigger stones. Anyone got a go-to mix for taller walls that holds better without adding too much water?

2 comments

2 Comments

gray_perez5226d ago

Got a buddy who used straight lime putty on his wall out in Oregon and it stayed put like glue but took forever to cure. I'd try mixing a handful of sharp sand into your Type S, maybe like a 1:1 ratio with your mortar sand, to help it lock in place without getting too wet. Thicker mix means less slump on those big rocks, just gotta work fast before it sets up. My wall's only 3 feet tall and I still had to baby the joints for a bit, so I feel your pain on that 40 footer.

stella90426d ago

Actually Gray, I don't think sharp sand is the way to go for a 40 foot wall. Sharp sand can actually make the mortar too stiff and brittle once it cures, especially on something that tall that's going to take a lot of stress. What you really want is a softer, more flexible mix that can handle a little movement without cracking. I've seen too many tall walls fail because the mortar was too rigid and the whole thing just popped apart in the freeze thaw cycles. Better to add a bit more lime to the Type S and keep the sand on the finer side so it bonds better with the rock. @gray_perez52 I get the idea of using sharp sand to add grip during placement, but on a wall that size, long term strength matters more than how it handles in the bucket.