[bluefoxicy]

I'm installing a floor soon and someone mentioned Ditra.

Which is better, Ditra or 1/4" Hardibacker? Difference between Ditra and Ditra XL?

I've installed Hardibacker before, haven't installed Ditra. I know what I'm doing with Hardi, never done Ditra. Easy enough for first try to get right? Worth learning?

Ditra seems somewhat flexible, which I'm uncertain about. That seems like it would transmit less movement from shifting wood under the ditra up through to the tile. On the other hand, it's flexible, so if there's pressure on the tile wouldn't it flex the Ditra itself?

Ditra doesn't bond to thinset. It's held mechanically, that's why it looks like a giant waffle. What are the implications here? Thinset bonds directly to Hardibacker and mortars the tile down solidly.

Budget isn't a huge issue. It looks like Ditra would cost $250 versus Hardibacker costing around $100 plus $30 of screws for this job. With the Ditra XL, the handbook seems to indicate that I could skip the additional 3/4 underlayment and still have the same structural strength, saving labor and a bit of money ($380 for that, and the subfloor will be $250 to put in, plus then I have to run more throughout the house, plus $130 for Hardibacker in the kitchen)..

Worth it or not?

 

[DannyT]

i used ditra the first time when i did our kitchen and again on the half bath. to me it was easier then cutting (ditra cuts with scissors or a razor knife) and screwing down hardiboard. and since it is 1/8 thick my tile ended up within 1/16 of an inch level with my hardwood flooring in the adjoining rooms. i plan on using in the bathrooms upstairs also. the ditra XL is just thicker for height adjustment. just like hardieboard you can tile right over it. installing hardieboard for me was more labor intensive than the ditra. with ditra you need to flatten the floor before installation, the hardieboard is flattened after installation

 

[bluefoxicy]

my floor is already flat. I have a 2 way level (a little T made of two bubble viewers) that I tried all over the floor and it shows the bubble between the two lines in all directions. So that's not an issue.

I'll go with the Ditra then. It looks like it's faster since you can get right to work laying tile without waiting for the thinset to set. Plus my floor is 1 1/8" (I worked it out, found some gaps and measured, etc) so I don't have to add underlayment this way. I'll scrap the screws and the 3/4 inch T&G plywood from this project.

Hmm... guess I'll put sill tape around the perimeter for expansion, and run the waterproofing tape over the seams and at the walls. I guess the bead of sealant goes on top the sill tape like in the diagram, then I'd fold the kerdi-band waterproofing barrier over that and thinset it to the wall, then install the molding over that and tack it to the wall... but how do I tack in the quarter round molding at the base? I can't just nail through the water barrier... puncturing it would eliminate the purpose. Also not sure what to do behind the cabinets... just leave the kerdi-band exposed, but thinset it to the wall?

 

[JazMan]

my floor is already flat. I have a 2 way level (a little T made of two bubble viewers) that I tried all over the floor and it shows the bubble between the two lines in all directions. So that's not an issue.

Sounds good, (how long is your level?), but that is not how to check the flatness of the entire floor. The reference is how flat within a 10' span. You need an 8-10' straight edge and then determine how much out of plane the floor is.

What is the 'sill tape' you're talking about? Why do you need this floor to be waterproof like a shower floor? Sounds like a regular room, kitchen or bathroom. Floors are not required to be watertight, plus it's almost impossible to do cuz of the doorways.

Jaz

 

[bluefoxicy]

Heh good point.

It's a kitchen. Waterproofing in the kitchen is in case of things like icemaker line failure, sink failure, dishwasher failure... things I've seen happen a few times. These are usually inside the kitchen.

 

[jeffnc]

It's a kitchen. Waterproofing in the kitchen is in case of things like icemaker line failure, sink failure, dishwasher failure... things I've seen happen a few times. These are usually inside the kitchen.

I actually kind of like that idea, even though it seems like overkill. But remember, it really does little good to waterproof the floor if you don't waterproof the edges up the wall. And then.... what?

You have to ask yourself, if water leaks onto my kitchen floor, where is the water going to go? It's certainly going to soak through the grout, and if you've waterproofed the Ditra seams, it won't penetrate to the subfloor there. The water between the tile and Ditra will start to migrate somewhere. If it's a refrigerator or sink or dishwasher, then most likely you're already right up against a wall. So let's say you apply Kerdi on the Ditra and up the wall a few inches. Now where will the water go? It will go toward the doorways or entranceways to other rooms. How are you going to handle that?

In bathrooms or clothes washer rooms, this problem can be solved by putting a drain in the middle of the room, and gently sloping the floor toward the drain from all directions. This is impractical in your kitchen.

I realize I'm playing devil's advocate, but the fact is I don't really know the answer to the question. There might not be a good solution for waterproofing a kitchen floor.

 

[jeffnc]

Budget isn't a huge issue. It looks like Ditra would cost $250 versus Hardibacker costing around $100 plus $30 of screws for this job. With the Ditra XL, the handbook seems to indicate that I could skip the additional 3/4 underlayment and still have the same structural strength...

Good for you for keeping the cost of the screws in mind - most people don't. Also, look for better deals for Ditra online (it's expensive at Home Depot.) Or if you know a contractor that will install your tile or has done some other work for you - they might have an account at a tile distributor and can get it for you cheaper. I pay about $1/sf.

As to Ditra XL, it does not replace structural subfloor. If your subfloor needs to be stronger, Ditra XL won't do it. Normally you won't need XL. The only time is if you really need more height to match a transition to another floor surface. Even this could be accomplished by adding 1/4 plywood first, but obviously using Ditra XL would save this step. But again it would be strictly for height, not for structure/strength.

 

[Hiro]

Could it be helpful to waterproof just the edges where the wall meets the floor to prevent water on the floor from reaching drywall? Like this, except around the entire wet area: http://www.northlandconstruction.com/products/2632/orig/kerdi-kereck FA Outside Corner.jpg

http://www.northlandconstruction.com/products/2632/orig/kerdi-kereck FA Outside Corner.jpg

 

[jeffnc]

That's the right idea Hiro, but again, the problem is - where is the water going to go? You can't do that when you get to a doorway, and the water will go in that direction into the next room.

 

[Hiro]

So...where do we want the water to go? How much does it absorb into regular flooring materials?

 

[jeffnc]

If you could keep the water contained in the room within the Kerdi "shell", then you'd notice the grout getting damp. At that point you could find out where the leak is, fix it, with no harm done. The floor would eventually dry out, but it does not harm thinset to be wet in the mean time. Thinset is basically cement and it can get wet just fine.

If this were a bathroom, you could slope the floor slightly toward the center and put a drain there. This is basically what some people do when they create a little tiled area for their washing machine. Slope the floor slightly and drain it.

 

[bluefoxicy]

What is the 'sill tape' you're talking about? Why do you need this floor to be waterproof like a shower floor? Sounds like a regular room, kitchen or bathroom. Floors are not required to be watertight, plus it's almost impossible to do cuz of the doorways.

http://www.schluter.com/media/brochures/DitraHandbook-2008-ENG.pdf

Page 14 references waterproofing the kitchen. Having had icemaker and dishwasher leaks, I understand that water moves around in inconvenient ways.

See page 21 utilizing a Sill Seal band as an expansion joint. I assume the sealant on top is a bead of caulk; Schluter sells some kind of Kerdi-Seal in a tube that appears to be silicone caulk.

As to Ditra XL, it does not replace structural subfloor. If your subfloor needs to be stronger, Ditra XL won't do it.

The Ditra handbook gives requirements for subfloor thickness and joist geometry. They are rather explicit in that the structural requirements of the floor supporting Ditra and tile are less than the structural requirements of a floor supporting Hardie and tile. Straight Ditra 1/8 inch on 3/4 of OSB with 19.2" OC joists or I-joists will work for porcelain tile; whereas you need 16" OC joists with 1.25" thick subfloor minimum for cement board.

Ditra XL is specified as required for more structurally unsound configurations in which Ditra is counter-indicated.

I'm certain a subfloor that won't hold a car will fail if you slap Ditra on it and park a car there; I think the indication is more that a subfloor that will not support a car properly to prevent tile delamination and cracking with cement board but that will retain structural integrity can adequately support a car without delamination and cracking within a broader range of specifications if Ditra is used instead. In other words: Ditra-backed tile is less susceptible to non-catastrophic deflection.

 

[jeffnc]

In other words: Ditra-backed tile is less susceptible to non-catastrophic deflection.

Right - the Ditra doesn't make your floor more structurally sound, it just makes it less susceptible to minor structural-related problems.

 

[jeffnc]

http://www.schluter.com/media/brochures/DitraHandbook-2008-ENG.pdf

Page 14 references waterproofing the kitchen. Having had icemaker and dishwasher leaks, I understand that water moves around in inconvenient ways.

Sure, it would be a good idea for kitchens. But notice they don't tell you how to handle doorways

See page 21 utilizing a Sill Seal band as an expansion joint. I assume the sealant on top is a bead of caulk; Schluter sells some kind of Kerdi-Seal in a tube that appears to be silicone caulk.

Kerdi-Fix isn't silicone, but silyl modified polymer - a type of urethane I believe. There are substitutions that cost less. A Schluter rep once recommended NP1 as an alternative if I couldn't find Kerdi-Fix locally. NP1 isn't all that easy to find either.

 

[JazMan]

Bluefoxicy,

I like and use Ditra whenever practical and when the customer isn't pinching pennies. We've mentioned several times that waterproofing a kitchen is not required and is nearly impossible to do, but I understand your idea.

You can waterproof the floor by using Ditra and Kerdi on the seams. But in order to contain water within the room you'd have to flash Kerdi up the walls a little too. Good, no problem unless the cabinets are still there. Good to do when doing a complete remod. You still have to deal with holes in the floor for water/gas/electrical tubes, and vents. And of course the doorways. So essentially you can protect much of the area, but it's difficult to make the unit waterproof.

The Ditra handbook gives requirements for subfloor thickness and joist geometry. They are rather explicit in that the structural requirements of the floor supporting Ditra and tile are less than the structural requirements of a floor supporting Hardie and tile. Straight Ditra 1/8 inch on 3/4 of OSB with 19.2" OC joists or I-joists will work for porcelain tile; whereas you need 16" OC joists with 1.25" thick subfloor minimum for cement board.

You misunderstood the requirements. CBU's can be installed over 5/8" ply and 3/4" ply or OSB over a variety of several spacings. No one requires 1.25" ply or OSB at 16" oc.

The deflection requirements are the same for Ditra and CBU's. (L360) Ditra does not give the floor less deflection, nor do they claim any such thing. It only helps for minor lateral movement, not vertical movement.

Jaz

 

[bluefoxicy]

Odd. I thought that the recommendation was 1.25" total after reading in several places that (primarily the official Hardi FAQ for use of 1/4 inch Hardi board to back tile), but now everything I read says 5/8 inch is necessary. There is much documentation of me citing the 1.25" requirement scattered around in forums and e-mails I have records of, but all sources mentioned in any conversation seem to corroborate 5/8 inch requirement now.

My floor is apparently 1.25" so it is no problem. I am used to facts changing.

You cannot turn a room into a pool; you can prevent water from immediately soaking through and finding its way to things it can damage. Given time, the situation may resolve itself if the flow is cut off; or you may need to intervene and remove some of the water.

My utilities come through the walls, not the floor. Was going to bring drain, water, vacuum, and electricity through the floor for the dishwasher; but we are extending a wall here to back that, so utility will come through that.

I always remove cabinets to lay tile. Cabinets are placed on top of tile floor. Pantry will be integral to structure and built before flooring, secured to the subfloor.