Ceramics Over Plywood?

Q: Can ceramic tiles be installed directly on a plywood subfloor? I’ve put down ceramics many times over the years, but always the old fashioned way, over mortar. A friend has asked me to help him redo his entrance with 18-inch square ceramics over wood, but I don’t know if I should. Do you recommend this type of installation?

A: I’m not crazy about applying ceramic tiles directly to a wooden subfloor, though lots of installers take this approach these days. From what I’ve seen, it's not unusual for installations of this sort to show signs of loose grout joints and occasional tile cracking. And with tiles as large as the ones you’ll be working with, the danger of cracks is a distinct possibility A better way to install ceramics without the need to lay down a good, old-fashioned (and labour-intensive) mortar bed is to use cement board. This is a rigid, reinforced masonry sheet material (about 1/2-inch thick) that's anchored to a wooden subfloor with ring shank nails and thinset tile mortar. Installing tiles on top of cement board creates a stable and reliable base, while saving considerable labour. Cement board is a Canadian invention that’s now used all over the world for tile installations.