Ben's Master Bath

[htimsneb]

First post so I hope I get this "right."

Background
I'm redoing my master bath (L-shaped 56 sqft, 3x3 shower) and to this point, I have ripped out everything down to the joists. I have attempted to level the floor via glued and screwed 2x6's as mentioned throughout the forum. I have blocked in 2x4s to supported otherwise unsupported edges and topped it all with 3/4" Advantech subfloor (heavy stuff by the way!)

My joists are 2x9 (true 2" width), 16" OC, 13' in length, unkown wood (house built in 1975) = L436 deflecto score.

I plan to put down Ditra and 12"x24" porcelain tile (that my wife likes it)

Question(s):

1. I feel like there may be some wave or slight unevenness in the floor and I know its not flat/level nor am I going to try and level it...just trying to achieve flat.

a. Will adding another layer of 1/2 plywood help even out the "wave" or if I'm screwing every 8 inches in the field will that only amplify any issues?

b. If there are any valleys, can I fill them with Ardex Wood or Henry FeatherFinish patch compound first?

2. The old sub floor was 1/2 plywood with a mortar bed on top. Due to wall and joist placement, I could not cut 2" of the exposed 1/2" subfloor out along one of the walls. Should I lay in another 1/4" x 1.5" strip to fill the void before putting underlayment on top over everything?

3. This is my first time putting down floor tile. Have I dug my own grave by attempting such a large format tile?


I'm sure I'll think of more questions but will tack those on later if I do.

Thank you in advance for not beating up the newbie.

[cx]

Welcome, Ben.

Beating up on newbies is seriously frowned upon hereabouts and once is the maximum limit for doing so. This entire website is designed to help just such newbies.

1. Flatness is a serious issue with large format tiles such as you have. The industry standards call for no deviation from intended plane of more than 1/8th" in ten feet nor 1/16th" in two feet. That's a very flat floor and you'll be glad to have at least that when you start to set those tiles.

Adding the second layer of plywood subflooring, which I'm always in favor of, will usually help to flatten out the floor. Not a lot, but some, and it won't ever, in my experience, make anything any worse.

2. You don't indicate what you intend to use as a tiling substrate over your wood framed subfloor. That makes a difference in further responses.

As I understand the void filling, yes, I would do that.

3. Possibly, but you needn't get into it just yet.

Photos of what you're working on are always helpful.

My opinion; worth price charged.

[htimsneb]

Thanks for the quick reply CX. I plan to use Ditra as an isolation barrier between my subfloor and tile.

Regarding the addition of the 1/2" plywood, does this need to extend into the shower space or is the 3/4" subfloor in there ok if a traditional mud and liner pan is to be installed later?

[Kman]

Then you definitely want to flatten the floor before your tile underlayment is down.