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PSA: mixing mortar too wet for a 4 foot garden wall in Tucson cost me a full weekend rebuild
I built a 4 foot garden wall behind my house two weekends ago and figured wetter mortar would be easier to work with in the heat, so I added extra water until it was like pancake batter. The first course went down fine and looked great, but by the next morning the joints had shrunk and cracked and the whole top course was leaning about half an inch off plumb. I ended up knocking down 3 courses, which was 60 blocks, and redoing it with a stiffer mix that just barely held its shape on the trowel. What I learned is that in 100 degree heat the mortar sets fast, so a wet mix feels easier but it never gets the strength or the bond you need. Waiting 10 minutes for the mortar to set up before I touch it made way more difference than adding water ever did. Has anyone else dealt with mortar drying out too fast in the heat, and do you add anything to slow it down?
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kelly_rivera3d ago
Isn't the real issue here just that you mixed way too wet in the first place, not the heat itself? I've laid plenty of block in Phoenix summers and a wet mix has always been the wrong move no matter the temp, because water is what kills the bond and makes the joints shrink. You said yourself the stiff mix worked fine once you stopped adding water, so it sounds like the heat was never the problem you were fighting. Waiting 10 minutes to let it set up is good advice, but that just means your mix was right, a wet batch would still slump and crack even if you waited. If you want more working time, mix smaller batches and keep the mud in the shade instead of drowning it. Adding stuff to slow it down is mostly a band aid for a mix that's too loose to begin with.
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