My tile game plan....any thoughts?

[ohio guy]

Hello all. I’ve enjoyed reading many of the posts here on the forum and have found them all to be incredibly helpful. I hoping that if I offer my game plan for a kitchen and 1/2bath ceramic tile job, I can get some feedback from those far more experienced than me. First, here’s what I’m dealing with: I’ve got ½” plywood subfloor glued and nailed over 2”X10” 16”oc joists that run 14’ (this yields a deflection of L/380).

My plan is to add an additional layer of ½” plywood laid in a way that it overlaps the joints of the existing plywood (leaving 1/8” gap between edges) and then screw the two together but not into the joists (I’ll be sure to 2” deck screws here, not drywall screws). Then I plan to use a modified thinset with pea soup consistency to attach the Ditra and use unmodified thinset with peanut butter consistency to attach the ceramic tile on top of that.

Any thoughts on brands, strategy, things to avoid/do, etc..would all be greatly appreciated.

Thanks.
Mike

[Muddman]

Sounds good. Remember to use modified thinset when you put down your ditra, and unmodified for setting the tile on the ditra. Pre filling the ditra waffles the day before you tile can be helpfull for a DIY'er.

[John Bridge]

Welcome aboard, Mike.

Not "pea soup"; more like tooth paste or a little looser. Not soupy, though. You've got to have enough substance to allow the ridges to stand up and grab the back of the Ditra.

Half inch plywood is hard to screw into. It doesn't have enough substance to grab the screws thoroughly When you crank down on them.. Be careful not to strip them out. And at the same time, make sure you don't leave voids between the two layers.

[astrojeff]

My suggestion here would entail additional prep work, but it might help alleviate the problem that John mentions. If you predrill your upper plywood layer with a drill bit that's the same diameter as your screws, it will be much easier to pull the two layers flush together and to judge when you have hit the correct torque. Even if you use those screws that have the smooth shank on the upper 1/2", there can be a lot of friction with the upper plywood piece so that it is tough to judge when you have pulled the two pieces flush but you haven't stripped the lower piece.

If you predrill, you can lay out your grid ahead of time, and it makes setting and drilling much easier if you don't have a dedicated drill gun. Just make sure to sand or deburr the bottom side after drilling, since the little pieces of wood from the drilling job can actually create voids.

[ohio guy]

Good to know about the toothpaste consistency. As for the advice on adding the additional layer of 1/2" plywood, I don't think I ever would have thought about the problem you guys mention. The predrilling idea would definitely add some prep time, but sounds like it'd be time well spent.

Thanks for the expertise!