Fresh Bath remodel, need subfloor info

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Old 05-13-14, 10:41 AM
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Fresh Bath remodel, need subfloor info

Hello, I have recently (2 months ago) starter master bath remodel. Everything is gutted out all the way to joists and all water, waist lines removed. I plan on adding a bath and moving stuff around. Anyway everything was going great untill I pulled the subfloor. It was 3/4" planks they were not solid. I discovered a large cut in the exterior wall beam to accommodate a drain line. The whole side of the house was cut to install the pipe in. Also lots of walls were hacked when copper piping was added. On top of that with the help of a laser lever I found that in 13' my bath floor is 2" out of level! Great. So far I have planked them down on one side and sistered up the other side to level the floor. It is now level and perfectly flat. Took one month btw. I dragged a long level to
Mark high spots and fine tune the floor. Joists are in excellent condition. They are 2x12 16oc, span is 13". I added more 2x12's and finished with 2x4 all the way around do the subfloor is properly supported. House is very level and no cracks. Foundation is in great condition. From reading these forums I think I'm ok with tile, or natural stone but I can't decide/ or find out if one sheet of 1 1/8 t&g ply is better than 3/4 and 1/2? 1 1/8 seams so much sturdier. I plan on 1/4 hardy on top and tile. I am attaching a pic. Am I missing anything? Thank you
 
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Old 05-13-14, 10:50 AM
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Oh, I forgot the best part, this is a two story house and bath is on second floor above the kitchen. To accommodate a new 3" main drain the whole house was cut from the roof (for the 2" vent) to the foundation. I sistered up the cut with glued 2x12 and added a 4x4 going across with bolts on each end. Anyway I believe this to be sufficient as I'm adding really thick subfloor and will install 3/4 ply
On that wall to sturdy everything up.
 
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Old 05-13-14, 11:34 AM
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Hi,

I can't speak to the framing repairs of the floor and wall.

I agree a single 1 1/8" t&g plywood subfloor is stiffer than 3/4 + 1/2". So you're fine for ceramic once the tile backer is installed into fresh thin set mortar, fastened and taped. If you wanna go natural stone you'd need a double layer of ply plus the Hardie, plus we'd have to go over those joists to see if they meet specs.

Jaz
 
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Old 05-13-14, 12:25 PM
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Hello, thanks for the reply. I thought that 1 1/8 t&g ply is ok for stone?
 
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Old 05-13-14, 03:54 PM
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I thought that 1 1/8 t&g ply is ok for stone?
I knew you'd come back with that good observation.

1 1/8" or actually I think it's 1 1/4" (?) is stiff enough, but, it needs to be in two layers. You're thinking; "doesn't make sense". The idea is the two layer allows a slight amount of isolation from the subfloor and the joists, this is key.

So, the subfloor is fastened to the joists, and the underlayment is fastened only to the subfloor. Then the concrete backer or preferably the uncoupling mat (Ditra) goes in further isolating the tilework from the stresses created by the joists.

It's also not very common that someone use 1 1/8" ply. That stuff is very heavy and there should be a law............. We usually find 3/4" ply or OSB as you know.

As for the 2x12" joists @ 16" oc spanning 13', and natural stone. It depends on the species and grade, but I think most commonly used species will be stiff enough for natural stone. You're positive they're 2x12"?

Jaz
 
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Old 05-13-14, 04:16 PM
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They don't look like 12's but you have doubled everything so it looks like you have taken due diligence and stiffened things up. Kudos on the foresight and effort put forth to date, you have done more prep work than most who have visited this forum. I think you will be OK moving forward, Jaz always wants the specifics (which is a compliment). You will save money, IMO, by going the 3/4" + 1/2" + backer board and tile. The 1 1/8" stuff will break your back as well as your bank.

What are your plans with regards to shower or tub in relation to the tile on the wall? Shower base or custom pre-sloped shower base with pan (DIY or ready built)?
 
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Old 05-13-14, 07:07 PM
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They are 12"s for sure, just slightly over 11" tall. I understand plywood sub floor uncoupling etc, but I don't get how first layer of plywood glued to the joins and second screwed to first with a ton of screws will be uncoupled? They will be one solid piece at this point so why not go with a single piece? *Disclaimer* in no way do I mean to doubt the experts or discredit anyone. I'm trying to understand what am I trying to accomplish and the physics behind it. I read that some people glue the second layer to first and not to do this would be a mistake. I appreciate everyones response and the time they take to read my post.
In regards to the shower I will pour a mortar base with pvc lining and than another later of mortar. If you couldn't tell I chose to do everything the hard way. This is my first bath remodel and I never ever want to do this again. It is depressing to walk in the bathroom and see it all gutted even though I've been at it for 2 months. I did add stuff along the way such as a sky light, moving walls etc...oh well time for a beer
 
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Old 05-13-14, 08:01 PM
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but I don't get how first layer of plywood glued to the joins and second screwed to first with a ton of screws will be uncoupled?
Well, it does. The recommendation is that you do not fasten the underlayment to the joists, just the subfloor. This way the underlayment is in less stress when the joists are under load. How much uncoupling? I don't know, but probably measured in the thousandths of an inch. There's also differences in temps and humidity that influence the top vs. the bottom layer. The uncoupling part is the best reason to use a membrane such as Ditra.

They will be one solid piece at this point so why not go with a single piece?
No they will not. To make them one you'd have to laminate the two layers of ply using a thin wood glue spread 100% & fastened quickly.

I read that some people glue the second layer to first and not to do this would be a mistake.
Most people would not laminate. If you squirt beads of construction adhesive you're creating small voids, air pockets, fasten only. Plus, underlayments are meant to be removed some day. Gluing causes problems when that's necessary.

As for your shower. I recommend a shower with surface waterproofing over the old traditional method. It's best that the top layer of mortar on the floor never gets wet from normal use. Plus with the traditional method there's no waterproofing on the walls above the curb.

Jaz
 
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Old 05-13-14, 08:35 PM
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Jaz you are the man. Now that makes sense. I understand that the tile floor needs to be almost separated from the house and simply rest on it perfect flat so the wood expansion etc does not transfer to the tile.
For the shower I plan on using redgard after all is said and done applying it on the mortar pan and sides with tile. Tile will go on top. I guess this is commonly done. I will still use the pvc liner in case redgard breaks down over time. I really don't mind doing the work but I do want it done right. Thank you for your suggestions
 
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Old 05-13-14, 08:39 PM
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One more question. I keep seeing people mention ditra v cement board. What is the difference? Home Depot has hardy in 1/4 and I was going to use it on the floor and 1/2 in the shower. It looks easy to use and cut. What is the advantage of ditra? I did not see at the home depot
 
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Old 05-14-14, 09:58 AM
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Ditra is a fantastic product and I recommend it highly. It's an uncoupling membrane, it can be installed to make a floor waterproof, (by sealing the seams and flashing up the wall a bit), on a slab it helps to equalize moisture, is easier and faster to install and raises the floor only 1/8" total. The only drawback is that it costs about double or more than 1/4" or 1/2" backers. But I think it's worth it.

Many of the HD & Lowes store carry Ditra in small 54 sq. ft. rolls. Good for diy'ers. You can also get it from a real tile store and maybe be able to buy just what you need.

Hardie backer; I rarely used it when I used CBU's. Harder to cut & dangerous to be around all the dust when cutting with a side grinder. But so are the others. The main complaint I have is that it's very thirsty, so it sucks the moisture out of thin set fast. You should damp sponge or mist just prior to applying.

The other issue I had was the necessity of installing expansion joints in the field in any room that was 15 ft. in any direction and when the room made an "L". I don't see that spec anymore though. What has changed? I suspect nothing at all.

Also note that Hardie 500 (walls) is thinner than 1/2". People have issues with that, esp. in remodeling.

Jaz
 
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