Question about mixing mortar for a chimney rebuild in the cold

I used to just add a little extra water when it was under 40 degrees, but after a repoint job failed last winter, I switched to using a non-chloride accelerator from a brand called Set-Rite. Anyone have a go-to cold weather additive they trust more?

4 comments

4 Comments

patricia2624mo ago

Set-Rite works but a heated water mix is a safer bet for a solid bond in those temps...

rowanhernandez4mo agoMost Upvoted

Heard about a guy who tried mixing Set-Rite with warm water to lay tile in a cold garage. He said he just wanted to take the chill off. The whole batch went off like a rocket in the bucket, turned into a crumbly mess before he could even get it on the floor. Had to chip it all out and start over with cold water the next day. I mean the bag warnings are there for a reason, maybe it's just me but I wouldn't risk it.

gray8754mo ago

Wait, you're mixing Set-Rite with HOT water? @patricia262 that's wild, the bag literally says not to go above like 50 degrees. You'll cook the chemicals and it'll set up way too fast. Cold water only for that stuff, man.

the_hayden1mo ago

Whoa, hold up, I gotta push back on the heated water idea. In my experience, messing with water temp is a gamble you don't wanna take on a chimney rebuild. I've seen guys try lukewarm water to speed things up and end up with flash sets that left weak joints. Set-Rite is fine if you follow the directions, but @patricia262, hot water can mess with the chemistry and make the bond brittle. Cold mortar that takes longer to cure is safer than a batch that goes off too fast and cracks come spring. Your mileage may vary, but I'd rather wait an extra day than patch a failed chimney next winter.