Questions & Answers

I'm installing 8" x 32" Porcelain Tile in my bathroom (9'x16'). I have 3/4" subfloor with 1/4" Exterior Plywood as the substrate. I'll be using Ditra Heat membrane.

Couple questions...

1. I used 1 1/4" screws to install the substrate placing them 6" apart (See attachment). Is this sufficient?

2. I checked the flatness of the floor to see if I have any variances. I used a 6' level and I have 1/8+" in one section. However, if I run a 3' level across the same section it's only 1/16". I'm assuming since my tile is only 32" in length this shouldn't be an issue but would like to verify.

Any best practices for the above?

Thanks in advance!!

Ken