Threshold Notch Size for Thinset?

[Chuck B]

Hi guys, I’m replacing a broken granite threshold and have installed a half inch hardie backer cement board underneath after carefully chipping out the grout adjacent to the tile.

Can someone please tell me what size and shape of notched trowel to use with the acrylic modified thin set? And should I back butter the threshold as well?

Thank you!

 

[Jadnashua]

First, make sure that you've applied thinset UNDERNEATH the HardieBacker.

Depending on how flat the threshold bottom is, and how much play you may need if you want it at a specific height, you want about a nominal 3/16" layer of thinset after you've set it in place and flattened the notches down. Technically, it should work with less ad some thinsets aren't designed for more. A thinset designed for large tile would help as it's less likely to let the heavy granite sink before it starts to set up during the curing process.

It's always a good idea to burn a layer of thinset onto the back of the tile, or in this case, the threshold prior to setting it. You'll get a much stronger bond when you do. Use the flat side of the trowel and push hard to embed the thinset into the pores of the granite.