tiling new bathroom-questions

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Old 12-29-10, 10:58 PM
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tiling new bathroom-questions

I am going to be tiling new bathroom and laundry room (part of large addition) 16" OC wood I-joists with 3/4" Advantech subfloor. I got 1/4" hardibacker board all cut and in place, but it is not yet secured to subfloor-wanted to lay it all out first to make sure everything fit OK. I have a contractor that is going to be working with me to do this. I am trying to have it prepped for when he comes next week. I will do laundry room while he does bathroom-that way I can get help if needed and learn. couple of issues have come up that I am concerned about. He said that he never puts thinset between backerboard and subfloor. says he has never had tile crack. He does have very good reputation per the regulating body in my state. he also told me to use 1 1/4" drywall screws. The hardibacker brochure says use #8 corrison resistant screws. The drywall screws are #6 and I don't know if corrision resistant. the guy said the screws they tell you to use are way more expensive and he has never had problem with drywall screws. I guess if you do everything right, the screws shouldn't be exposed to moisture after thinset sets, correct? So, should I insist on thinset between subfloor and hardiboard? the floor is solid and I made sure no nails sticking up, scraped all drywall mud off of it, and could even plane the subfloor seams if necessary. and should I use the screws made for hardibacker? 5lb of drywall screws is $20. the others are sold by quantity so hard to compare but an approximately equal size box of them, holding 800 screws, is $25. have no idea how many drywall screws are in 5lb box. but this is only about 165ft2 job so I can't see cost being that much of issue?
 
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Old 12-30-10, 06:56 AM
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I,m not a tile pro but here's my experience. Use the manufacturer's screws instead of the drywall screws. I tried drywall screws once and had difficulty with getting the screws to countersink flush with the hardibcker. I also had some screws snap off. I've used roofing nails for cbu on walls but I'm hesitant to use them on the floor although I think it's an improved fastener.

I have put down hardibacker with and without thinset between the subfloor and the hardibacker. I could not tell the difference and I'm not sure what it is supposed to accomplish. Especially if you follow the recommended fastener spacing. It is recommended in the manufacturer's install instructions though.
 
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Old 12-30-10, 07:02 AM
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. Screwing the cement board into wet thinset insures there are no air pockets under the cement board. While drywall screws might be ok in a dry location, the proper screws won't rust and are designed for the application.
 
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Old 12-30-10, 08:20 AM
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All cement board manufacuterers require that their board be bedded in a fresh bed of thinset. This is a necessary step, as the thinset fully supports the board, and guarantees that their are no voids between the board and the subfloor. Typically, if you do not use thinset under the board, you'll develop hairline cracks in the grout sometime down the road. It could be several years, and the cracks can be so fine that they are hardly noticeable. You could be one of the lucky ones that might not have a problem, but why take the chance. Since you know the right way, insist that it be done right.

Good luck trying to use drywall screws on hardi and getting them set flush with the board. You'll have lots of screw heads popping off and great difficulty getting the screws set properly. You know the right screws to use. Again why use the wrong ones.

The few extra dollars you spend to get the job done right will be well worth it. Specially, if you don't do it right and have issues later.

Manufacturers put their products thru lots of testing, and know the best way to get guaranteed results. They are a lot smarter than me, you and certainly your installer. While you say your installer has a good reputation, I'd wonder why since he does not follow industry standards. My personal opionion, I'd be looking for an new installer. Go to hardi's website and read up on the proper way to install their board. Insist that the installer do everything according to their instructions or get a new installer.
 
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Old 12-30-10, 08:27 AM
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It is recommended in the manufacturer's install instructions though.
Wayne, its not recommended, it is required. Not trying to be picky about your response but just trying to clarify for the op.
 
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Old 12-30-10, 10:47 AM
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you guys are right, I know the right way(what the manufacturer recommends), so why not do it that way. so if I am going to try to put down hardibacker by myself, I have few questions. It says use modified thinset. what exactly does that mean? how is it "modified" and is it different that what you use for the tile? what should I be looking for at homedepot? and when I am laying it, do I put enough thin set for one sheet, lay the sheet and then screw it down? or do I lay them all and then screw them all down at once?

and once I put that down, do I have to let it set for a day before walking on it or laying tile?

one last thing, what is approximate total height above subfloor for everything (thinset, 1/4" hardibacker, thinset, tile)? I was not planning on tiling where vanity cabinet (84" long cabinet) is going to be and had placed 3/4" plywood in that area, cutting it a bit short so the tile will be slightly under cabinet. will that be sufficient? to be honest, I probably should have just put down tile there as well since I am doing it and the cost of extra tile will not really be much. just wasn't really thinking and didn't calculate cost cause when planned for kitchen and hardwoods, I did it this way cause the amount of area was quite large and the hardwoods were not cheap (3/4" engineered in maple-I think $7sqft!) so that was quite a bit of savings in doing it that way.
 
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Old 12-30-10, 12:38 PM
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Home Depot carries Custom Building Products line. The bag you are looking for will say Versabond on it. That'll be good for under the cement board. Use a 1/4" notch trowel for the thinset. Just do an area large enough for 1 sheet of hardi. Immediately set the sheet in the thinset and then screw it down to the subfloor according to the screw pattern on the board. The screws will draw the sheets down tight, and the actual thickness thinset included will be approx 5/16" give or take a little. total thickness of everything will depend upon the thickness of the tile, the size of the tile, what the backs of the tile look like, and what size trowel you will need to use.

Make sure you gap the hardi sheets and tape and mud them according to the manufacturers instructions.

You can walk on the cement board and start setting the tile immediately if you'd like.
 
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Old 12-30-10, 12:50 PM
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havseen the name versabond. used that brand of subfloor leveler where addition met the old house. so do they only have one "grade" of thinset and I use the same stuff to lay the tile?

I used the 4x8 sheets of hardi. they don't have the grid pattern on them like the 3x5 sheets. but it says screw them every 8", 3/8" from edge and 2" away from corners in the install guide. so that is what I will do. the gaps are as close to 1/8" as reasonable I guess. never gonna be exactly right cause rooms are never perfectly square. but since there will be baseboard moulding, a little extra gap shoudn't hurt.
 
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Old 12-30-10, 01:18 PM
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Lotsa different thinsets. What kind of tile are you planning on using?
 
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Old 12-30-10, 02:07 PM
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leaning toward Marazzi 16x16 tiles at HD. they are 3/8" thick by my measurement. HD site says 1/3" thick?? strange measurement. some others that we looked at are 12x12 and only 5/16" thick.
 
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Old 12-30-10, 08:17 PM
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It says use modified thinset. what exactly does that mean? how is it "modified" and is it different that what you use for the tile?
No, it's not any different.

A "modified thin set" means a "polymer modified thinset", and that simply means a thin set to which a powdered adhesive has been added. Mixing that thin set with water activates the powdered adhesive and so your thin set will then have greater adhesion. The thin set will stick to the substrate better and the tiles will stick to the thin set better. And, being a "polymer" (ie: a "plastic") the resulting thin set will have greater flexibility and elasticity as well. Normally, cementatious materials (like thin set) will have almost no flexibility or elasticity. But, the more plastic there is in the cured thin set, and the more it will bend and stretch before it breaks.

Some thin sets have so much powdered glue in them, that they can be used to set tile directly over plywood.

Here's much the same thing being sold to the general public:
DAP Weldwood Plastic Resin Glue
Mix the powder in the tub with water, and you have a general purpose woodworking glue.

Hardibacker and your tile manufacturer will both probably recommend you use a polymer modified thin set everywhere; under the Hardibacker, in the hardibacker board joints, and to set the tiles. You can use the same polymer modified thin set for all of these jobs.

Not all polymer modified thin sets have the same amount of glue in them. The more glue, the better they stick, but the harder that thin set is to remove in future (should that become necessary). Your contractor's point of not using any thin set under the tile backer boards is well taken because it allows you to remove that ceramic tile and install a different kind of flooring (like synthetic rubber floor tiles) without having the big job of removing the old thin set off the floor.
 

Last edited by Nestor; 12-30-10 at 08:46 PM.
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Old 12-31-10, 05:12 AM
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Better Options

A tile job should be done as though it's going to be there forever, be wet, and have lot of weight moving around on it.

For that reason, I would not skimp on a layer of thinset or the proper screws. Contractors like your friend are masters and making a job look okay in the end for the customer while keeping costs down. This is why I try to do all my work.

A tile guy I know swears by Superflex tinset. Cost a bit more and no one wants to pay it, even though they may be throwing down tile at $10 a square. Superflex allows some movement, to it reduce fractures. With 16-inch tiles, unless your floor is very level, I'd do whatever I could to reduce the chance of fracturing.

My next tile job will use SCHLUTER DITRA Tile Underlayment. It's cool as hell. It's a decoupling membrane that costs about $1.33 to $1.50 square foot. But that's not that much more once you figure the cost of the Hardi AND the screws. Plus, it's a light, rolled good -- so you roll it out over thinset (no screwing). Getting this down takes a fraction of the time of cement boards -- It's waterproof and fracture resistant.

Again. People will fret over the tile selection and pay through the nose per square, then not want to pay $10 more for a bag of Superflex. Like McMansions -- Look nice from the curb, shoddy underneath. This is what is wrong with our country.
 
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Old 12-31-10, 10:46 AM
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I think I saw that underlayment you talk about. orange with one side has like fabric and other has raised squares. Thought about it, but thought it was "new" and some of the new things aren't as good as the old tried and tested. cost wasn't issue. I used 5 boards of hardibacker and about $20/sheet so $100 for my approx 155 sqft bath and laundry and $50 in correct screws. Of course I was way more efficient at my cuts than most would be and had very little left over-5 sheets is 160 sqft so only 5 sqft leftover. the membrane would have cost about $200 but been much faster to install I'm sure. Like I said, it was just that I wasn't sure how well it worked and how long it has been tested in installation. will it last forever or will it have some kind of issue after 5 years in use? -new isn't always better. Like CFL's that are all the rage. sure they use less watts, but you flip switch and the room is still dark for 2minutes. and if you drop one and break it good luck. read the stories about those that have high mercury levels and had to quarantine off room cause they couldn't afford to pay $2000 to have company come in to remove mercury! So I know backerboard has been around a long time and there aren't any major surprises going to happen. I know my floor is level and very clean without dips. this is new construction BUT has been settling for 2 years! My first GC went bankrupt- built foundation too high, framed 1st floor and was 2" too high, removed it, and then went bankrupt. 2nd came in and built shell, and i have been slowly doing most everything myself. so hopefully most settling will have occurred by now. I will look into the thinset options.

of note, I am paying for and acquiring all materials and I am paying this guy by hour for labor, with me helping. so that at least eliminates him charging me for the "job" and just trying to get it done quickly using poor materials. he will use whatever I get. if I get the "right" screws, that is what we'll use. I appreciate all the help from this site so I do get things done right.
 
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Old 12-31-10, 01:51 PM
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Your contractor's point of not using any thin set under the tile backer boards is well taken because it allows you to remove that ceramic tile and install a different kind of flooring (like synthetic rubber floor tiles) without having the big job of removing the old thin set off the floor.
And will also void the manufacturers warranty if and when you have a failure. We really should not be advising someone to do something other than what the manufacurer requires on this forum. Manufacturers and the entire tile industry spend lots of time and money on testing, and there are indeed reasons why they require what they require. Don't skip the thinset under the cbu.
 
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Old 01-01-11, 12:28 PM
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No, John, I now that the purpose of setting the Hardibacker in thin set is to prevent possible movement of the tiling underfoot.

I'm just saying that at some point in the future, when the OP or some future owner of that house decides to remove the ceramic tiling in favour of some other flooring, getting that polymer modified thin set off the old underlayment is gonna be a fight.

We should advise the OP that that he should count on replacing that underlayment if he ever takes that ceramic tiling out. Either that, or nail down a layer of 1/4 inch plywood underlayment over what he has now, and install the tiling over that new underlayment. That way the new underlayment could be pryed up to avoid having to remove that thin set from it.
 
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Old 01-02-11, 06:04 AM
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Either that, or nail down a layer of 1/4 inch plywood underlayment over what he has now, and install the tiling over that new underlayment.
Nestor, there is no 1/4" plywood acceptable to be used anywhere under ceramic tile. The minimum is 3/8" exterior glue cc plugged. That being said, adding more plywood is always a good idea if you can afford the height.

If the job is done right, there should be no need to replace the floor for many, many, many years. I'd never install a ceramic tile floor worrying about how I might demo it in 20 years or more.
 
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Old 01-02-11, 10:19 AM
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OK, looking at thinset last night. keeping in mind someone above mentioned superflex (which I guess is the lowes brand with additive to make it flexible), I see HD has flexbond. it allows some flexibility. it is 26.99/bag vs the 13.99/bag for plain versabond. so if I get the flexbond, should it just go under tile, and use versabond under hardibacker? or vice-versa? or flexbond both places? and funny thing when i visited website for custom building products (maker of versabond and flexbond) they mention suitable substrates wonderboard specifically but don't say any other cemet boards? do they also make wonderboard?? I assume these products are OK with hardiebacker? and white is $3/bag more. no reason for me to get white if I am using ceramic or porcelin tile? doing reading, seems like white is just needed for light colored stone? is that right?
 
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Old 01-02-11, 12:56 PM
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Versabond is CBP's low end modified thinset. Use it under the cement board. Use the Flexbond to set the tile.

Superflex is a Tec product and a fine thinset it is. You'll find it at tile stores but not big box stores. Lowes carries either Mapei or Laticrete setting materials, good stuff also.

And yes, CBP also makes wonderboard, so they push their board. You can use Versabond with Hardi.

Thinset will typically purge thru the grout joints as you set the tile. If you don't clean it all out of the joints as you go, you'll see the color of the thinset mixed in with the grout later on. For that reason, most say use grey thinset for darker grout colors and white thinset for lighter grout colors. The white and grey thinsets will do the same job.
 
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Old 01-02-11, 08:12 PM
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OK, after searching for superflex last night, I found that laticrete additive is called superflex adhesive (or something like that) and I assumed that is what was meant by superflex. I think the tec site was down last night when I looked.
 
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Old 01-03-11, 01:08 PM
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The Flexbond that you found at HD is a good thinset as well. You can use that to set the tile.
 
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