How Long Does Thinset Take To Dry On Backerboard . Click to see full answer. Try to apply thinset when the temperature outside is between 50 and 100 degrees. How to install brick flooring ReFabbed from www.re-fabbed.com However, it will almost always need between 24 and 48 hours to dry before you can grout your tile. Grinding sounds like a lot of work, a lot of dust, and less than ideal (flat) results. Also asked, how long does thinset take to dry on backerboard?