Preparing bathroom floor for tile

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Old 03-16-11, 02:55 PM
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Preparing bathroom floor for tile

I'm remodelling a small hall bathroom (maybe 4'x8' floor space) in a home built in 2004. I intend to do 12" ceramic tile. The floor currenly has vinyl. I haven't pulled it up yet, but from the basement I can tell it's OSB.

Looking through other threads I see these questions asked a lot when people want help, and I need some help answering them:

What size are your floor joists - How do I tell the "size"? What dimension do I measure?

What is their on center spacing - I can find this.

What is their unsupported span (span between supports from below)? - I can find this.

What kind of subfloor do you have. - How can I tell the thickness if I can't see an edge. Based on other things I've seen I suspect it's the thinnest the builder could get away with.

What kind of tile will you be using - Ceramic, 12"
Ultimately I want to know what I need to do to make my floor suitable and not prone to cracking. My dad has tiled his bathroom twice and still has cracked tiles and it looks aweful.
 
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Old 03-16-11, 05:21 PM
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Weez, go up under the room with a tape measure and measure the joists, from top to bottom. You probably have 3/4". A way to tell is to drill a 7/8" or so hole in the floor and stick a ruler in the hole. Sort of like looking from the side, but cheating.
You get us those measurements and we can give you better advice. We're here.
 
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Old 03-17-11, 11:40 AM
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Ok, I have some info:

The joists are 18 inches tall. The average spacing appears to be 24" centers although I found one that was 27" in the area of my bathroom and the one beside it was 22".

The unsupported span in the area of the bathroom is 15 feet.

The OSB is stamped 23/32 inch, so just under 3/4.
 
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Old 03-17-11, 01:02 PM
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A related question: Should I pull out the vanity to do this job? If so, on what surface should the vanity ultimately rest?
 
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Old 03-17-11, 05:14 PM
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You don't have joists, you have trusses. Confirm that, please. You can take a picture and post it if you want. http://forum.doityourself.com/electr...your-post.html
I would pull the vanity. The new one will rest just fine on the new tile, and if, 5 years down the road, you decide to change vanities, you can change the footprint without problem.
 
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Old 03-17-11, 05:37 PM
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Old 03-17-11, 07:33 PM
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There ya go! Trusses. You have plenty of support, but between the trusses the general consensus is to have 1 1/4+ of subflooring for your tile. Once this is installed, you would apply a notched trowel layer of thinset and install concrete backer underlayment or Ditra, then more thinset on top and your tile. You will obviously have a transition point from the bathroom to the hallway or other room which will need to be addressed with a transition strip.
Others on the forums may give you better news or advice, so hang in there for more answers.
 
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Old 03-17-11, 08:19 PM
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Ok, I'll pull up the existing vinyl and see what's underneath. I will remove any laun as well.

How can I tell if there is laun or plywood underneath? I've never seen laun.

I'm trying to determine how much thickness I will add to the floor all said and done. So if I add up the additional plywood subfloor, backerboard, ceramic tile, and two layers of thinset, then subtract the existing vinyl and laun, how much thickness will I be adding?

The answer to this question will determine if I proceed with the project. I think it will look wierd (plus be a tripping hazard) if the bathroom floor is much taller than the hall carpet.
 
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Old 03-18-11, 04:21 AM
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If you add an additional 1/2" plywood and 1/4" cbu (concrete backer unerlayment), plus your tile possibly another 3/8 w/ thinset, you would be looking at possibly 1 1/4". But, remember your carpet is probably 3/4" thick with padding, so although you may be above that plane, a transition strip will not make it too obtrusive.
 
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Old 03-18-11, 10:59 AM
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I think the first step is to determine exactly what you have for a subfloor/underlayment. Drilling in an inconspicuous spot as Chandler suggested will answer any questions about what floor height you may end up with. Luan plywood is commonly used as a underlayment for vinyl but that doesn't mean it's what you have. A lot depends on the builder.

Remember that a custom fit threshold can compensate for some height difference and you can reduce the floor build up a bit by using a membrane instead of backer board.

I know it's subjective, but usually smaller tiles look better in small bathrooms.
 
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Old 03-18-11, 11:30 AM
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Would ditra be a better choice than cbu since it's a bit thinner?

I have to tear out the vinyl anyhow so I'll probably just do that to see what's underneath.

What size tiles would you suggest?

Exactly what brand/style of mortar should I get for both the subfloor-ditra and ditra-tile bonds?
 

Last edited by Weez; 03-18-11 at 01:07 PM.
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Old 03-18-11, 02:09 PM
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Weez

Drill a hole in the floor as has been suggested. That way, you can determine the different layers of subfloor and underlayment that you have. This is important, as any 1/4" underlayment for the vinyl has to go as well. It's likely you have some kind of underlayment for the vinyl, and that underlayment will not be acceptable for ceramic tile. You can remove the vinyl and underlayment in one shot, by cutting thru it with a circular saw set the depth of the vinyl and underlayment. Cut it into 2' sections and pry it up with a hammer and pry bar.

Add at lease 1/2" of bc or better exterior glue plywood over the osb subfloor. Since you have 24" oc spacing, more plywood is better, as this helps to eliminate deflection between the trusses.

Yes, by all means use ditra instead of the cement board. It's thinner and does a better job of uncoupling movement than cement board does. Use a good quality modified thinset under the ditra, and a good quality dryset mortar (unmodified) over the ditra. Don't use cheapo thinset.
 
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Old 03-18-11, 03:17 PM
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If the existing underlayment is plywood, why can't I leave that in place? Is it the wrong type/grade of plywood?

Won't I end up taking off a bunch of the OSB subfloor when removing the existing underlayment? Will I need to do anything to repair that?

What are the "good quality" mortars? Will it say modified and unmodified? I'm not familiar with this stuff at all.

Since this is a bathroom, do I need to do anything to the perimeter of the underlayment or tile in order to keep water spilled from the tub/toilet from getting under the tile?

Thanks!
 
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Old 03-18-11, 04:46 PM
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Weez

Underlayment for vinyl is usually 1/4" material. There is no 1/4" plywood or other vinyl underlayment that is acceptable as an underlayment for ceramic tile period. The vinyl underlayment is likely nailed or stapled to the subfloor. It may be a pia to pull up but very doable. The subfloor should be fine, remove any stray nails, staples etc.

Modified thinset has an additive mixed into the mortar. The bag will indicate some kind of wording like "fortified" "polymer modified" or something similar.

Dryset mortar is just that, a mortar that doesnt have an additive mixed in.

There are many good modified and unmodified thinsets. I'm not sure what you have access to. As a general rule, don't buy the cheapest stuff on the shelf. With thinset, you definintely get what you pay for.
 
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Old 03-18-11, 05:47 PM
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Ok, so the underlayment is not glued down then. That's what I was worried about.

I checked lowes because it's next door. They sell Mapei brand that says "with polymer". The most expensive is about $30 for a 50lb bag. They also have some w/o polymer. They only have 50lb bags.

I'll check home depot and a nearby hardware store and see what they have. We also have a Menards but it's on the west side.
 
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Old 04-23-11, 10:30 PM
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Ok, so I took a break from this project to get some other stuff done.

I just tore up the existing floor and have one issue. By the HVAC register I pulled up a strip of the subfloor maybe an inch wide and 3/8 thick. What's the proper way to repair this?

 
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Old 04-25-11, 01:28 PM
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A copule additional questions, before I start cutting the 5/8 plywood to put down on the existing subfloor:

How far into the doorway threshold should the tile go? Just in line with the bathroom wall? Or should it protrude out into a doorway a bit to meet up with the carpet?

The carpet comes in to about the halfway point. I don't want to get the tile so far away that I can't get a transition strip (or the transition strip would be so big it would look dumb).

Also, since my bathroom is small, is it OK to just use a singe sheet of plywood or do I need any kind of seams with gaps for thermal expansion?
 
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Old 04-25-11, 02:13 PM
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Best rule of thumb is the floor covering for the threshold should end where the door covers it from the room into which the door opens......confusing? If you have a bathroom door that opens into the bathroom, let the tile end even with the door stop molding. That way you will see carpet in the hallway/bedroom, and the tile won't be seen until the door is opened. Some like to split the door stop, so either way is good. You don't want tile showing in the bedroom/hallway with the bathroom door closed.
 
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Old 04-26-11, 07:58 AM
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Cool, thanks.

Any advice on my question in post #16?
 
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Old 04-26-11, 01:27 PM
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Find the piece and glue it back in place or use Minwax epoxy wood filler to fill the area and sand it down. You will be installing cbu over it anyway, right? This is for tile?
 
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Old 04-27-11, 08:08 AM
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Actually I'm putting 5/8" plywood down then Ditra.

I'll try the epoxy, I think I might have some actually.
 
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Old 04-27-11, 02:13 PM
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Good move adding another layer of plywood to the floor. It'll make the floor a lot stronger and add some additional insurance that your tile installation will last a long time.

Before you install the second layer of ply, check the floor, and add screws as needed to make sure the subfloor is solidly secured to the joists.

Make sure you use the right plywood. It should be exterior glue, cc plugged or better. Dont use glue, just lots of screws, and avoid hitting the joists with the screws. Stagger the seams so they do not line up with joints below.
 
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Old 05-02-11, 02:44 PM
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Looks like my subfloor is nailed down. So I'll add some screws just to be safe.

I'm still concerned about the threshold. Is there a certain transition strip I need to use for thick carpet to tile? I don't want it to end up looking odd due to the height difference.

Here is roughly how my threshold is currently set up. I'm thinking that I should butt my 5/8" plywood right up against that 1/4" strip that's already there?

 
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Old 05-02-11, 04:50 PM
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I like to use a marble saddle/threshold for the kind of transition from a bathroom to a carpeted hallway or other room. The saddle takes up the width of the door jambs. The tile gets cut and grouted to the saddle, and the carpet gets cut and tucked to the saddle. If there is a higher than desired height transition from carpet to tile, the carpet can be "ramped up" to compensate for the height difference.

The 1/4" strip of wood under the carpet is the tack strip, yes?
 
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Old 05-03-11, 07:57 AM
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Yes, now that you mention it it is the tack strip.

Do you have any links to pictures or where to get this saddle? I'm not familiar. I guess I need to familiarlize myself with this method so I know how far into the door jamb my additional plywood should go.
 
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Old 05-03-11, 11:02 AM
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You can buy them at any retail tile store. The big box stores have em as well, but sometimes slim pickens there. Heres a link for what I'm talking about. I'm sure you have seen plenty of them.

Marble Thresholds, Granite Floor Saddles - Distributor, Wholesale, Import
 
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Old 05-04-11, 07:51 AM
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OK, I get it now.

So that gets thinsetted into place. Does it overlap the tile, or is it right up against it? I'm trying to visualize how it all fits together with the carpet and tile.
 
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Old 05-04-11, 08:46 AM
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Second layer of plywood, then ditra, then the marble saddle set in thinset. Leave a space between the tile and the saddle for grout. The saddle height will be a little higher than the finished height of the tile.
 
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Old 05-05-11, 07:50 AM
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Ok, that makes sense.

How do I "ramp up" the carpet to match?
 
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Old 08-22-11, 11:34 PM
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I had to put this project on hold for a while, but I'm back at it. I have a couple of Ditra questions:

1. Before installing the Ditra, do I need to fill in any knots in the subfloor? I screwed up and installed the 1/2" plywood smooth side down, and there are a couple of repaired knots showing that are about 1/8" deep. Will the thinset fill this small gap, or do I need to do something else?

2. Do I need to do anything special to the seams between the sheets of subfloor before installing the Ditra? What about the seams in the ditra itself?
 
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