Another sub floor question

[pap79]

I want to install 12 x 12 ceramic tile in a two room bathroom. one room has tub and toilet, the other room a six foot vanity cabinet. room 1 the floor to cover is 5 x 3, the other room to cover is 4 x 6 1/2. There is a door between the rooms.

the underlayment is 1/2" particle board. Under the particle board, which I know I will have to remove, I think, there is 1/2 " plywood. the joists are 2 x 10 on 16" centers, they span about 13'.

My concern is that the extra subfloor layer will have to be thick enough to support a tile floor, and as a result the new floor will be considerably higher than it was. My bottom line question is. What thickness of plywood subfloor should I add to the existing 1/2 "? What ever is needed, I don't nail the new layer of subfloor to the joists, is that correct? Thanks, Rich

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[cx]

Welcome, Rich. :)

First thing I'd have you do is remove the maybes from the equation. Let's measure the actual unsupported span of the joists and the thickness of the subflooring. Then we'll talk.

There are some ways to lower the subflooring if necessary, but let's determine if it's necessary. And having the floor a little higher isn't usually a big problem. You'll lose a little toe-space under the cabinets, and might need to raise the toilet flange (or add spacers), and maybe make a reducer to the floor outside, but none of that is a big deal at all.

My opinion; worth price charged.

[pap79]

The unsupported span of the floor joists is 13'6". Sub floor is 1/2 " plywood.

Thanks,
Rich

[pap79]

I see mentioned in the forums, ditra, I went to their web site, but still don't quite get what it does. Does it replace hardi backer board for underlayment?
If it does, I could use 5/8" plywood subfloor over existing plywood subfloor instead of 1/2". I want to raise the floor as little as possible. Please explain this ditra to me, a totally ignorant do it yourselfer, nervous about my first tile job, but too cheap to pay for a pro to do it.

Thanks
Rich

[cx]

Please keep all your questions for this project on the same thread, Rich. Helps others who might want to help or learn keep up with what's going on. No one could give you advice on your current question without knowing what you already have for a floor, for example. :)

Ditra does, in fact, replace CBU as an underlayment in a floor installation. It also offers isolation properties superior to that of CBUs (in theory, at least). You could add more plywood and use Ditra to remain at the same heigth as less plywood and CBU and have a better floor. I would say that 5/8ths is about the minimum thickness plywood you should add in your situation anyway, Ditra or CBU. Ditra is more expensive, but easier to install; CBU is less expensive, but more work. Your call.

If you choose Ditra, you can got our online store and find Tile-Experts.com and order your material from our friend David Taylor. He'll sell you as much or as little as you need and give you good advice on its care and feeding.

But for an avowed cheapskate, you might prefer CBU. :D

It's not a difficult thing to transition between floors of different heights.

My opinion; worth price charged.

[pap79]

I've torn up my floor. I'm down to plywood subfloor. I need to put some screws into the joists to hold the floor down better, seems a bit loose to me.
What kind of screw do I use? Drywall screw, deck screw ?
I will then add a 5/8" bc (is that correct?) subfloor over that. What screws do I use to attach that? I'm all screwed up.

Thanks
Rich

[cx]

I like deck screws for that, Rich. At Homer's you'll find a convenient 1 5/8ths length. They're a lot stronger than sheetrock screws and longer lasting.

I also recommend pre-drilling the plywood to prevent "jacking." Pulls it down to the joist a lot tighter.

My opinion; worth price charged.

[pap79]

If I am going to put a layer of subfloor over my existing subfloor and screw it every 8", and then put a layer of 1/4" hardibacker, screwed every 8", how do I avoid screwing the hardibacker screws right on top of one of the subfloor screws. If this is a stupid question, I apologize. But I need to know.

Thanks,
Rich

[Davestone]

Rich, that is the stupi......er a reasonable question, to which i reply..you'll have to do the best you can,you will probably hit a few, just move your screw over a little,or lay them out opposite of the other ply...you know one has a screw in the corner, and on the other go 2" from the corner and run them.See what ya got him into CX! :)

[cx]

Oh, sure, blame CX. :rolleyes:

What did I do? Jist tole him to pewt plywood. Plywood is good. Lotsa screws is good. It's all good, Dave. Go take a nap. :D

Rich:

If you screwed your plywood at 8 inch centers (shoulda been 6 inches on the edges), and you're fixin' to use the same schedule for your CBU, you shouldn't have any interference problems on accounta you won't have your CBU joints anywhere near the same place as your plywood joints. Just start a CBU joint half way between a row of screws in the plywood and you'll never hit a screw below. Nope, won't happen.

And there ain't no stupid questions hereabouts. Answers? That's another story. :cool:

My opinion; worth price charged.

[GregS]

Just to stir the pot a little bit, I found this on the Hardibacker website FAQ:

----------

Q: Why can't I put Hardibacker directly onto concrete or other subfloors?
A: Hardibacker ceramic tile backerboard is not designed for use over concrete. The minimum subfloor specified is a 5/8" exterior grade plywood or 3/4" exterior grade OSB (Oriented Strand Board) subflooring with a deflection not greater than L/360 for live and dead loads over joists that do not exceed a span of 16" on center. Our installation conforms to TCA (Tile Council of America) guidelines as well as the tile industry as a whole. The TCA does not recognize compressed sheets or wood planks as suitable subfloors for a tile application.

----------

I thought it has been mentioned here that the TCA (IIRC) specifies 1 1/8" minimum subfloor.

[pap79]

The ditra matting really appeals to me. Seems to me that it is easier to install than cbu and takes up less height. I am willing to pay the heftier price for ditra if it will make my life easier and do the job. Any thoughts on ditra.

Thanks for this forum, I can study my project to death.

Rich

[cx]

Not sure which pot you meant to stir, Greg, but I see no contradictions in the Hardi comments there. No manufacturer or industry organization recognizes sawn board floors as a suitable subflooring for installation of their tiling substrate, if that was your point. But that's why we always tell people they must install a layer of plywood over such flooring. That does comply, and the board flooring does provide substantial rigidity, just not the dimensional stability necessary. With the addition of at least half-inch plywood, the subflooring is quite adequate over 16 inch spacing.

The TCA has methods of installation of CBU over single layers of plywood and OSB over such joist spans. Those are minimum requirements. We always recommend that people use more subflooring than that, though.

Rich:

If you do just a tiny search here under Ditra, you will find thoughts enough to keep you reading for much longer than it will take to install the product.

Basically, most folks agree that Ditra is a good and useful product. If that's what you elect to use, I'd recommend you visit their website and read about the product. Ditra (http://www.schluter.com/english/products/2002/sectionf/ditra/601-ditra.html#substrates)

My opinion; worth price charged.

[pap79]

I cut out the toilet flange in my bathroom. The key way for the toilet bolts was in the wrong orientation. If my put my new floor around the flange, I would not be able to get the toilet bolts in due to the higher floor. Here is my question. Should I replace the flange on top of the new subfloor, or install the toilet flange after the tile is set? It would certainly be easier to install it on the subfloor, I wouldn't have to drill thru tile. I want to do it properly but I want to make it as easy as possible.

Thanks,
Rich

[Mike2]

Rich, the "ideal" setup is to have the flange sitting right on top of the finished floor (tile). You can cut some notches/slots in the tiles that will fit under the flange such that drilling holes for the fasteners is not required later on.

[pap79]

OK, I'll do the toilet flange on top of the finished floor. The idea of notches rather than trying to drill screw holes thru the tile is neat.

That brings up another question I have. How do I drill a hole in the tile for a 1/2 " cpvc supply line that comes up thru the floor? I'm going to use ceramic 12 x 12 tile.

For the other few cuts I have to make in the tile, by the tub, the toilet flange hole, a heat vent in the floor. Do I rent a wet saw, or is there a blade I can buy for my side grinder? I thought I could buy one of those little cutters that dremmel makes, but the package says they are not for floor tile, just wall tile. Is floor tile too hard?

Thanks for all the help.

Rich

[Davestone]

Home Depot sells a ..holesaw...to fit on a drill,that'll work on ceramic.You can use a diamond blade on a grinder,it might chip a little. :)

[pap79]

I have cut 5/8 plywood for my subfloor. One room 3x5, the other 4x6 with a door in between. Is there a certain sequence I should use to screw it down? Should I start in the middle and work out, at a corner and work in, or does it matter. It doesn't sit flat on the floor at this point, the screws will pull the subfloor down flat, but I want to make sure I screw it down in the proper sequence.

Rich

[tileguytodd]

I generally start in the center of a sheet and radiate out.this helps the sheet to settle flat slowly.This is particularly useful with sheets that really seem to curl like 3/8"

[pap79]

I am in the process of screwing 5/8 plywood down to my origional 1/2 " plywood origional subfloor. Here is my question.

I'm using 1 1/4" deck screws and some of their heads are not exacly flush with the surface of the plywood, If I back them out and try to re drive them, they strip out. I am pre drilling a hole thru the 5/8 as was suggested earlier.
Is detra forgiving enough to allow a few screw heads that are not perfectly flush? or should I pull out the screws and counter sink them with a counter sinking thing a ma jig? Thanks

Rich

[bbcamp]

There is some forgiveness for the screw heads, but tile works best of truly flat floors, so the fewer bumps and ridges, the better. Besides, it's like the cat. It has 9 lives, but it doesn't want to waste any. You don't want to take a shortcut early in the process that will cause you to take another and another as you go on. Eventually, you find yourself with a problem you can't easily fix.

[pap79]

I fixed all of the screw heads that were slightly sticking up. My subfloor seems real solid to me.

I read in a thread somewhere, that the seam in the subfloor and the space around the perimeter should be caulked. Is this correct? I'm going to use ditra as the underlayment.

Is there a product that should be "painted on the plywood subfloor (bc plywood) to promote adhesion of the thinset or should the thinset be applied directly to the plywood and then the ditra?

Thanks for the input

rich

[tileguytodd]

Using a good modified thinset you will not need to worry about adhesion.With top quality Modifieds the plywood layers will give before the thinset will let go of it ;)

[pap79]

Thanks Todd,

How about caulking the seams and perimeter?

rich

[tileguytodd]

You can do that,you can also add expansion material to make sure you have enough room.frost king weatherstripping for example in 1/4" thickness.this will give you something to butt to insuring 1/4" expansion at perimeter and fills that dirt catching area.it eliminates the need to caulk before putting your baseboard in or at the least saves on the amount of caulking you will need :)
Some folks use it, some dont even fill the perimeter gap.Your call :)

[pap79]

I'm actually going to get this project done next week. But I have one more question. Maybe several.

I'm laying 12 x 12 ceramic tile that is 1/4" thick, detra as the underlayment.
I'll be buying thinset from home depot. The ditra literature says to use modified thinset between the plywood subfloor and the ditra. Is versabond fortified thinset what I need here? Between the ditra and the tile the literature says to use unmodified thinset. Is masterblend standard thinset what I need here?

Do I mix both of these with staight water or somethng else?

I'll use a 3/16 v notch trowel to set the ditra. Is a 1/4 x 3/8 square notched trowel the correct size for laying the tile?

One more. What is the difference between modified and unmodified thinset?
and why use two different kinds?

Thanks again,

Rich

[bbcamp]

Your choice of thinsets is correct. Mix both with water only.

Modified thinset is regular thinset (portland cement and fine sand) with latex or acrylic polymers added for strength, flexibility, and stickyness. Modified thinsets need to dry out as well as cure, so Schluter recommends that you don't use modified thinset between two impermeable materials, like
Ditra and procelain tile or concrete.

[pap79]

Thanks Bob for the explanation of thinset. How bout the trowel, is 1/4 by 3/8 the correct size to use for 12 x 12 tile.

rich

[pap79]

I got my ditra installed yesterday. That was fun. How do you professionals mix thinset. I almost killed myself trying to mix a half a bag of vesabond to lay the ditra.

I bought one of those paddle mixer things, put it in my skit xtra tool. it turned about two revolutions in a five gallon bucket and started smoking. I had to finish it by hand.

Is there a trick to mixing this stuff? Can I mix the thinset in a plastic concrete pan with a hoe. Seems like that may be easier. Thanks.

Rich

[cx]

The real trick is to buy a bigger drill, Rich. I suppose a fella could mix the stuff in a mortar box, but it sounds like a bit of a pain to me. The ol' drill and bucket method is the most common, but it does require a stout drill.

My opinion; worth price charged.

[jdm]

Rich --

Besides being easier, a drill and paddle mix the thinset to a smoother consistency than is attainable by hand. That makes setting tiles a bit easier, and you want every advantage you can get.

[pap79]

I found some grout at Home Depot, My wife likes one of the colors. It is Traffic Master Stain Proof Grout, it is pre-mixed. Is it any good? Thanks.

Rich

[jdm]

RIch --

That TrafficMaster stuff is not real grout. No cement- or epoxy-based product can be premixed. It is basically sanded caulk in a tub. The pros wouldn't even use the stuff in their mother-in-law's house. :) Do a search on TrafficMaster and read their comments.

That said, I believe that the TrafficMaster grouts copied their colors from Custom's Polyblend grouts, also carried at HD, so you should be able to find you color in a real grout.