Installing marble tile floor in bathroom

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  #1  
Old 09-26-12, 03:33 PM
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Installing marble tile floor in bathroom

I just removed everything from the half-bathroom in our house to install a new marble floor. I removed the old ceramic tile and noticed that it was installed on the subfloor or what seems to be plywood base installed over the subfloor, not entirely sure.

Now, I really don't know much about flooring but I always assumed that tiles were installed either on a cement floor/backer board or a mortar bed over wood subfloors. So im trying to decided whether to just scrape off the old cement and install right over the existing plywood/subfloor or add a cement backer board before installing the new tiles. My only worry is that this will raise the floor and come in the way of the water line and the drain for toilet, as well as not lining up with the wood floor in the house.

Any advice? Is there something else you guys suggest that wont add too much height?

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Old 09-26-12, 04:55 PM
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Your options sort of depend on what you have for sub-flooring, underlayment and how much work you want to do. Options also depends how much time and effort, tools available and skill set.

First question is: did you have any bonding issues or cracks with the tile you removed?

Second question is: It sound like you have a sub-floor layer and a underlayment layer of plywood. Can you confirm you have two layers of plywood or determine what thickness these layers are? Can you see the joists below? How well supported is the floor? Size of joists, span, how close to a bearing wall below?

Essentially your assumptions about using either backer board or a mortar bed to set tile are correct.

You could add 1/4" backer board set with thinset and screwed down for a much better base to set the tile on, this would basically raise your floor by 3/8" assuming the same tile thickness. The threshold could be raised the same amount, many houses have transitions like that at doorways. The base trim can also be raised fairly easily to accommodate this change. The supply line and the toilet drain can also be modified by any competent plumber.

I am not recommending this, but if you want to do the absolute minimum, I would suggest scraping more, maybe a little work with a belt sander to get the plywood as clean as possible. Then I would use a liquid bonding membrane over the plywood you have, then thinset the tile. This will help with bonding and may provide a small amount of isolation to resist cracks.

There are many ways to approach this project, the ones listed above are just the most simplistic and are based on limited information and a few assumptions.

My suggestion is to always take the time to do it right the first time. At this point I don't have enough information to tell you how to do it right.

Good Luck!
 
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Old 09-26-12, 07:06 PM
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Thanks for the reply. I took a closer look at the floor and it looks to be a 3/4" plywood underlayment. I thought about removing the plywood and then installing a backer board as you and the home depot guy suggested, but decided not to. I never had any cracking in the tile. They were just getting old and dirty and we had a toilet leak few years back that stained some of the tiles. I spoke to the home depot rep and he told me about an alternate underlayment called easymat. It's a thin adhesive that goes over plywood/subfloor. It should only raise the floor about a 1/4" and shouldn't interfere with the water lines or toilet drain.

As far the as the cement goes, I haven't removed any. What you see in the picture is what it looked like right after removing the tile, which literally came out in 10 minutes without breaking any. I only had 2 hours to work on it today. I plan on scraping off all the old cement and going over it once with an orbital sander i have, then laying down a thin set mortar then the easymat.

So, hopefully this works out well. I'll update with pictures.
 
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Old 09-27-12, 06:36 PM
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I would strongly urge you to use a 1/4" concrete backer underlayment thinsetted to the plywood and screwed in at the prescribed pattern. I would also suggest you choose something besides marble for flooring. It will show every bit of dirt that is tracked across it and will be a bear to keep clean, as well as being slick as.........well you know. I know it is a personal preference, I just have to throw in a couple of cent's worth of been there stuff.
I am not sure easymat is compatible with flooring. I have used it for backsplashes and it's OK, but marginal.
 
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Old 09-27-12, 08:35 PM
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The requirements for natural stone tiles are much more stringent than with ceramic tiles. The floor joists and subfloor/underlayment system has to be thicker. We still don't know how the floor is built. You said you think the floor is 3/4" underlayment. How about the subfloor? How about the joists? Chances are the joists do not meet minimums for marble.

Tell us the; type and size of the joists, species and grade will definitely help too, on center spacing, (usually 16"), and the unsupported span down to the inch. Also the type and thickness of the subfloor and what's over it?

Let's start there, but there's more to it than that.

Jaz
 
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Old 09-27-12, 10:08 PM
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I decided to go ahead with the backer board because it was much cheaper option than using easymat and also because you guys suggested. Now instead of laying the backer board on the plywood underlayment, which was slightly water damaged, I decided to pry it up and lay it directly onto the subfloor.

Well, I removed the underlayment and noticed some pretty bad water damage of the subfloor around the toilet and it was slightly warped causing it to bulge a little at the seam. This was caused by a leaking toilet wax ring we had few years ago. Our basement wasn't finished then, so no one ever went down there and the leak went on for about a week before we noticed. So now I'm not sure whether i should replace the subfloor damaged area or leave it and apply some sealer and moisture barrier before installing the backer board.

The underlayment was actually 1/2" not 3/4" as i said before. I checked the floor joists and they are 16" on center and it is a 1" subfloor. I posted some pictures of the bathroom before removing the plywood and after and a third pic of the damaged area from the basement water heater closet. You can see that some of the floor joist is also slightly damaged.

As far as choosing marble goes, i mainly did it because I got an amazing deal on some beige tiles at $2/tile a while back at home depot. I dont expect the tiles to get too slick or dirty because its only a 25 sqft bathroom. So there is very little moving space and usually the bathroom mats we lay down help to keep the floor dry.

Anyways, I would definitely like some advice on what to do with the subfloor and whether the floor meets the requirements for natural stone.

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Last edited by nishom21; 09-27-12 at 10:23 PM.
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Old 09-28-12, 11:12 AM
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Ok, looks like you have osb as your subfloor. Are you sure about the 1" thickness, I've not seen osb in that thickness, most I've seen is 3/4".

You need a second layer, preferably plywood for a total thickness of 1 1/4" for any natural stone installation. Over that, you need a tile friendly underlayment such as 1/4" cement board or a sheet membrane.

Your floor needs to be twice as stiff for a natural stone installation than ceramic tile. What size are your floor joists, what is their unsupported span. You have already told us that they are 16" oc.

You should replace any rotted water damaged osb subflooring. As to the floor joist damage, it just looks like some water staining in the picture, but hard to tell from here. If thats all it is, then nothing to worry about.
 
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Old 09-28-12, 01:55 PM
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You should absolutely replace any water damaged subfloor and make sure your patches land on joists (as in on center). I also think you will find that the OSB is 3/4". Mold and dry rot can be issues even if you think it is dried out now.

I would not recommend laying the 1/4" backer board directly over the subfloor, replace the underlayment, then add the backer board. You could use a thinner underlayment to accommodate adding the backer board and maintain you original thickness, seen it done many times - just a question of whether you want to do it right.

IMHO it is worth modifying the plumbing, threshold and base trim to accommodate the added thickness of the backer board to have it done right. This assumes you have proper joist spans below that are properly supported.

An ounce of prevention is worth a pound of cure.
 
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Old 09-28-12, 05:36 PM
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You could use a thinner underlayment to accommodate adding the backer board and maintain you original thickness, seen it done many times
Thats not the case. For natural stone you need 1 1/4" or more of plywood/osb. If the subfloor is 3/4" then the second layer of plywood needs to be 1/2". You cannot use anything thinner.
 
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Old 09-28-12, 07:01 PM
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Okay, so i took a closer look at the floor and I'm trying to figure out where to cut it. The subfloor is 3/4" OSB (not 1" as i had said before, sorry I cant measure ). The problem Is the the toilet drain is so close to the joist that they ( the home builders) actually had to round cut half the joist to put it in place. They also have two adjoining subfloor boards running directly through the middle of the drain. So initially i figured i would just cut down the joist where the drain is and replace the subfloor.But I really dont want to put the drain hole on the new subfloor at the edge , like the builder did. Now to go along with that, the area directly behind the toilet drain and where the water supply line is, is very badly damaged to the point where the subfloor is soft. I figured i could cut it back half way to the next joist, which is behind the wall, and then place some 2x4 underneath to reinforce where the seam will be. I also plan to do this on all 4 sides. I figured that very little pressure will ever be applied directly behind the toilet once the tiles are laid out. Also, this way i can put one single peace of subfloor with a cut out for the toilet drain instead of it being right at the edge. I attached a picture to give you a better idea of what I'm talking about. The other cut towards the bottom left will be on the joist, you just cant see it in the picture. Please let me know if i'm planning this right.

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Now as far as the backer board goes. I spoke to a home depot rep and he said that for natural stone the minimum requirement is 1 1/4" including the backer board. So i figured i'd just install the 1/2" backer board over the 3/4" subfloor and it would meet the requirement. Now if you guys think that a plywood underlayment is necessary, I will go for it.

As always, thanks for the input, I really appreciate it.
 

Last edited by nishom21; 09-28-12 at 07:18 PM.
  #11  
Old 09-29-12, 04:32 AM
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Unfortunately, people wearing orange aprons are not typically a good source for tile info. Cement board is not structural, it only serves as a good bonding surface for thinset. No manufacturers of cement board make any claim as to adding strength or stiffening a floor. 1/4" cement board is typically for floors, and 1/2" typically for walls. You can use the 1/2" on a floor if you need to make up some height but it will not make the floor any stronger. For your installation of marble, you need another layer of 1/2" exterior glue plywood cc plugged or better over your osb. The will give your floor the added stiffening between the floor joists that is required. There are rules, and I am not the one who makes them, however I do know them.

Remove all the damaged osb. Install blocking wherever necessary to install your new subflooring wherever necessary.

You still have not addressed the floor joist questions, and they are important if you are looking for a successful installation of your marble tile.
 
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Old 09-29-12, 08:16 AM
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I have attached a floor layout of the bathroom. The joists are 2x10 and 16" on center, I'm not sure of the species or the grade but i attached a picture, so hopefully that helps. Please let me know whether the cut I'm making in the previous picture is correct and anything else I may need to do for proper installation of marble tiles.

As far as underlayment goes, I will go with 1/2" plywood. Can you suggest which type of plywood would be best? And I'm assuming i would just nail this over the subfloor? Also, is it recommended to install a vapor barrier using 4 mil plastic sheet, or this mainly done for walls only?

Thanks again.
 
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Last edited by nishom21; 09-29-12 at 08:47 AM.
  #13  
Old 09-30-12, 05:17 AM
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Im not exactly sure from your diagram what you are intending to do. You need to make your cuts on joist centers wherever possible and where you cannot, you'll need to add a joist, blocking or something else for proper support.

As to the plywood you need Exterior Glue plywood cc plugged or better. It doesnt get nailed to the joists. It has to be screwed to the subfloor and you should try to avoide the joists. Your screw pattern should be every 6" in the field and every 4" around the perimeter of the sheet. Make sure that the plywood edges do not line up over the subfloor joints, they should be staggered. Use deck screws that are just loing enough to come through the bottom of the subfloor by approx 1/4".

You still havent told us the unsupported span of the joists. This is the distance between supports for the joists from below. Basically the length of the joists between whatever they are sitting on, like an exterior block wall a beam, a load bearing wall etc. As has been previously said, your joist structure needs to be twice as strong for natural stone and you likely will need to do some work to make the joists stiff enough.
 
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