The Brew Cabin

Thanks for such an informative site! I live in Colorado and it's starting to freeze overnight. I want to get my flagstones mortared as soon as possible. Hopefully this weekend.

My question is whether it is too cold for me to do this, and if not, is there something different in terms of mortar mix I should be using?

MM

If I remember from my days of srwiting specifications, you can lay at 2 degrees on a rising thremometer or four degrees on a falling thermometer. However that is in the UK, and I guess it depends on how quickly the temperature falls and rises in your neck of the woods.

You can buy additives that allow you to mix at lower temperatures, but I don't know what they do to the strength of the mortar.

Your memory serves you well, Jon. 2 degrees and rising is the minimum temp in which we'd use any mortar or concrete, and although the 4 degrees and falling is 'tolerated', if the temp falls to below 1C, then there are serious implications for the long term strength of the mortar/concrete.

When building civil structures, such as bridges or roadways, we'd use frost-proofers and/or accelerants to ensure we achieve the required cured strength, but, for pointing flags this loss of strength isn't all that critical, and as a very rough-and-ready rule of thumb, I'd allow pointing to takle place as long as there was four hours of frost free surface and air temp following placement, and I always like to cover such pointiung with hessian or similar to keep off the worst of the frost.

For Mr Mayer in Colorado, I'd suggest having a word with whatever it is that passes for a building supply company in that part of the world. The frostproofers we use in the UK and Ireland might not be suitable for the very low temps you experience, so it's always best to seek local knowledge and see what they recommend.