Rich & Kim's Bathroom Remodel w/pics

[Racer X]

The tub is in drain and all plumbing is complete. Ready for Phase 2- Floor questions...

Below, I've supplied a quick condensed illustrated views (before, current and possible after options). Option 1 is using CBU & Option 2 is using Ditra -just in case you wanted to see what I'm up against. When I pulled the old floor up (fig1), I found that the tile was mortared to 1/2" plywood. The 1/2" ply was nailed directly to 3/4" subfloor. There was no mortar between the 2 sheets of wood. I guess 1/2" wood the builders idea of underlayment. The tiles came up to easy which means it was installed wrong. Questions...

1. If I do the CBU route instead of Ditra, do I absolutely need a layer of modified Thinset under the CBU? I'm leaning torwards this one because the 1/2" ply continues into the hallway and the height total will be about the same.
2. Is it a good idea to apply mortar directly to the 3/4" Subfloor? Sounds like a mess if it ever haas to be redone and I don't think I can put down 1/2" plywood first then CBU- I worry about height.
3. Will I need the 1/2" ply on top of the 3/4" ply for strength anyway? Keep in mind that I'm using 12" Porcelain tiles in a small 8x8 bathroom.
4. I want to confirm that modified is applied under and unmodified applied on top of underlayment?
5. Why wouldn't modified be used on everything (top & bottom)?

Thanks ~Rich

[Racer X]

Oh, I also want to ask for recommendations on thinset manufactures... What are the favorites? and where do I purchase them?

Thanks once again.

[cx]

1. Yes, absolutely, unless you can find a manufacturer that says otherwise.

2. No.

3. It's a good idea. Technically you could use 3/8ths ply. Half inch would be better.

4. What's the underlayment?

5. Manufacturer's requirements.


Option 2 is the clear winner.

Lots and lots of brands of thinset out there. All thinset manufacturers make at least a couple good lines. Find a brand that's convenient for you to purchase.

If you need more help selecting in the chosen brand, we'll help.

My opinion; worth price charged.

[gardner]

Personally, I hate adding floor height where I don't have to, and if I add floor height I'd rather do it with plywood that will enhance the strength and rigidity of the floor, than with CBU which is just a substrate. In my recent project I went with Ditra at the suggestion of many here and although amazingly expensive for what it is, it was easy to use and added only 1/8 inch to my floor thickness.

My totally uneducated opinion is to follow option 2 which adds strength to the floor with an extra 1/2 inch of plywood and then use Ditra.

[Racer X]

4. What's the underlayment?

I was thinking ALL underlayment manufactures require Modified under and unmod on top.

Lots and lots of brands of thinset out there. If you need more help selecting in the chosen brand, we'll help.

What is the choice brand from HD? Or do you have a pers preference?

if I add floor height I'd rather do it with plywood that will enhance the strength and rigidity of the floor

Makes total sense gardner.

So that's 2 votes for option #2. from question 2, I thought my spidey senses where telling me NOT not to put any kind of morter/thinset on top of the 3/4" subfloor- which means I'll be screwing down the 3/8" or 1/2" ply. every 6"?... which means that I'll be installing Ditra because of height. Yer right, I see that Ditra is only 1/8". How much do you think the thinset layers will add to my total height?

Thanks a ton

[cx]

There is only one brand of thinset available at Homer's, Custom Building Products. CBP no longer offers a good-quality dry-set (un-modified) mortar. You need dry-set, you gotta shop somewhere else.

Homer does sell VersaBond, a modified thinset mortar that is good for most common applications.

It is worthwhile to follow these guidelines to the extent feasible when in stalling your plywood.

Installed Ditra should consume about 3/16ths of an inch in height.

My opinion; worth price charged.

[Racer X]

I'm ready to install the floor. I will screw down 1/2" Bcx on top of the existing 3/4" subfloor. Then I will place Ditra on top of that then Porcelain tiles.

Question,
1. What kind of screws do I use? I have 1-1/4" outdoor deck screws or do I use regular drywall screws?
2. 1/8" gap between the plywood panels and 1/4" at the walls suitable?
3. How thin does the mortar have to be to penetrate the white cover on the Ditra?

[Racer X]

Ok, I re read the link above (very helpful). It answered my "gap" question but I still dont know what type of screws to use... maybe I'll just buy Ring-Shank nails as described in that link. I suppose I'll research Ditra to see if there is more info about the mortor consistency needed as well.

[Brian in San Diego]

Rich,

1. The 1 1/4" deck screws are perfect. No drywall screws ever.
2. Yes.
3. Mix the thinset a little on the loose side. The imbedding happens by forcing the Ditra down into the thinset. I've heard of lots of different ways...large jobs - a weighted roller like you'd use on a lawn, a rolling pin, a piece of 2x4, a wooden float...lots of different ways but force has to be applied to the Ditra to get it imbedded properly.

Brian