Designing Kitchens and Bathrooms - Applying kitchen floor ceramic tiles

Hi,
I'm getting ready to tile my very uneven kitchen floor. Reading other threads has enlightened and confused me. About 20 some years ago we had our hillside house jacked up and a finished daylight basement put under it. Recently, while looking at the kitchen floor level we realized that the foundation for the basement was not installed level. The back wall is apparently about an inch lower than the front wall while a center bearing wall is even lower. This results in a floor that slopes to the middle with height differences of up to 2 inches. I need to level this floor for the tiles. I checked the deflectometer and the floor joists are quite adequate. The subfloor is 1-inch 1X10 planks (nonT&G) covered with 1/2 inch particle board. We currently have a vinyl sheet material as the flooring. What combination and sequence of materials should I use to level the floor? Is it ok to leave the vinyl in the worst areas since it would be covered by a wood product; vinyl-plywood-cement board (slc?)-slc(cement board?)-tile layer. I will be doing the work myself(no previous floor tiling experience but good general handyman with wall tiling experience). I'd much prefer to add to the current subfloor as opposed to tearing it all up and leveling the joists but want to do the job only once.

Thank you,

Steve

Hi all,
I am going to put down ceramic tiles on my kitchen floor. I will have leveled it by pulling up the old subfloor, rippers to the joists to level them (double full dimension 2X10, 24"O.C. 12' runs), then 3/4 inch T&G advantech, then 1/2 inch plywood, then what? I need an underlayment for the tiles. I gather either hardiboard or a product called Ditra is called for. I'd prefer Ditra because it's thinner but seem to remember others somewhere saying application is problematic These are my questions
1. Ditra or cement board?
2. How is either of these attached to the plywood?
2. Should the plywood be glued to the advantech.
3. Should the plywood to attached to the joists or just to the advantech?
I know its's a lot of questions but your help will be greatly appreciated.
Thanks,

Steve

Ditra is a excellent product, but way more expensive then hardiebacker. Hardiebacker is also a good product.

Hardiebacker gets laid in a bed of thinset AND is screwed to the subfloor.

Ditra is just thinsetted.

If your budget permits, I would go with Schluter Ditra. Ditra is 1/8" thick.

1) Ditra, much less labor intensive and out performs cement board.

2) See OK's post above

3) No, the plywood gets screwed to the advantec only. Do not use glue. Fasten every 6" around the perimeter, every 8" in the field, use deck screws, 1-1/2 to 1-5/8" long. Go in straight rows so you remove any bowing. You do not want to hit any joists. Per American Plywood Association guidelines, the second layer gets installed face grain crossing the joists and the short edge should get installed such that it ends 2" past the joist, not on a joist. Per Schluter guidelines, the plywood underlayment should be installed the same fastenning schedule as above, but the short edge of the plywood should end at the 1/4 point space between the joists or at 6" past the centerpoint of the closest joist. In all cases, you want a 1/8" gap between panels, 1/4" perimeter gap and long edge of the underlayment panels should be at least 1' away from the closest long edge of the subfloor panels. Confused yet?

By the way, the second layer of plywood needs to be underlayment rated plywood, graded as cc plugged and sanded, bc sanded or ac plywood. Do not use anything stamped as cd or sheathing rated. they have too many voids within the layers to be used for supporting a ceramic or stone install.


Hot brought up the fact that Ditra is 2x the price of cement board. At regular retail, yes, the material is much more expensive than cbu. But when you add in the almost $2 sheet for the screws and tape, and increase the labor intensity by a factor of 10 and time by a factor of 4 for installing cbu vs ditra...well you get the picture.

One roll of Ditra 30 (323 sf) weight about 40 lbs. One sheet of cbu is about 40 lbs. How much longer will it take you to carry 21 sheets of cbu from a truck vs 1 roll? After all that carrying, will you feel like doing any more work that day? How many wall dings will you have by the time you are done carrying it all in?

I realize that retired means you don't need to factor in time as much and I envy that. But I want you to remain retired and happy, and not to become retired and hurting.

Tilebri & HotinOKC,
Thanks to both of you. I feel so much more confident about tackling this job now. I understood your instructions and analysis. Now the work can begin:) Oops one final question. Is there any reason not to put cross-supports between the joists?

Steve

I would hope they are there now. You floor system is almost at the bare minimum for a ceramic install being 24" oc (I just caught that bit of info from your first post) If you really want a "drive a tank across it" floor, sister those joists with 8 footers glued and nailed to the side, lined up with the bottom edge. 2x6's 0r 2x8's would suffice.

the floor is sistered 2X10 (actual size) now. I was going to sister a third joist where the span seems to warrant it. There are no squeeks in the floor. I located the weakest part of the floor and if I jump on it there a bowl of water placed on the floor doesn't ripple on the surface. The floor is uneven now because when we had the house (on a hillside) lifted and a daylight basement put under it ( 20 yrs ago), the contractor did a lousy job of making the foundation level. We didn't realise it until now. There is sheet rock directly on the bottom of the joists and it hasn't cracked in 20 years. I hope the floor tiles don't cause cracking. Anyway thanks for the info on sistering and cross supports.

Steve

OK, here's what I have done so far. In the main section of the remodel, the kitchen proper, I totally removed the subfloor made rippers, leveled the joists by gluing and screwing down the rippers. I then glued and screwed down 3/4 in. advantec. The maximum height of rippers so far is 1.75 inches. The maximum distance between level and the remaining joist tops is probably about 2.5 inches. The remainder of the floor to be renovated consists of two smaller spaces adjoining the kitchen; a hallway/pantry (5X12 ft and a second hall/refrigerator+ freezer space 5X8 ft). Now I have a couple more questions:

1. I assume the screws I'm using for the Advantec should pass through the rippers and penetrate the joists by at least an inch, right?

2. My level height for the joists is now above the 1 in. planks on the remainder of the remodel area subfloor. i've removed the particle board and vinyl flooring. Can I leave the planks in place and sandwich them between the joists and necessary rippers? I'd add screws to the planks and glue and screw the rippers to the plank surface. My concern is that the planks will not be glued to the joists, but It seems to me that the planks can contribute to the rigidity of the floor if properly attached to the advantec.

3. Does the application of tiles using Ditra need to be completed in one continuous operation or can it be done over a period of several days?

Thanks for your assistance

1. Yes, but if you put another layer of ply over the 3/4", then it gets screwed to the substrate only, and not the joists.

2. I'm not sure how this will work out in regards to floor deflection.

3. You can lay Ditra using a unmodified thinset and start tiling immediatly, or later, but make sure the Ditra is perfectly flat. You don't want to lay the Ditra and finish another day to find out it wasn't flat.

Thanks for answers #1 & #3. Regarding #2. sounds like I probably should just rip up the planks like on the rest of the floor.

Thank you,

Steve

You can lay Ditra using a unmodified thinset and start tiling immediatly, or later, but make sure the Ditra is perfectly flat.

Uh uh. Modified over plywood or osb with ditra. Unmodified to set the tile though.

Can I leave the planks in place and sandwich them between the joists and necessary rippers?

With 24" oc spacing you need at least 1 1/4" of plywood or osb to minimize deflection between the joists. Remove the planks is the way to go.:)

Uh uh. Modified over plywood or osb with ditra. Unmodified to set the tile though.


Good catch! It's Schluter Kerdi that needs unmodified to keep warranty.

OK, All the planks are coming off. I will am following all the other suggestions you all have made. So far, the finished subfloor is level and feels nice and solid. Thank you very much.
I remain "retired and happy" not hurting. :D

Steve

Here's what I did. Removed subfloor down to bare joists, leveled joists with ripper shims on top of joists(nailed and glued), added cross braces wherever appropriate, nailed and screwed 3/4 inch Advantech, screwed 1/2 inch AC plywood to advantech (not to joists) and have a great new level floor. Now for the modified thin-set followed by Ditra, followed by unmodified thin-set followed by ceramic/porcelain tiles.

Question: Do I prime the plywood before applying the modified thin-set and if so, what should I use?

Thanks for your interest.

I merged your thread with this one in the Flooring forum, so some posts may look out of sequence.


No priming needed. If you'd like, do a scratch coat first. Take the flat side of the trowel and burn in the thinset into the subfloor, then trowel as usual and apply the Ditra.

No need to do anything at all to the plywood floor. Just use a modified thinset as required.

Schluter has an installation manual for ditra that will give you everything you need to know. Go to the Schluter website and check it out.:)

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

I have fixed my subfloor so it is ready to go. I am ready to start the tile-laying using Ditra. I have a couple of questions concerning expansion joints before starting .
First, the easy one. The final plywood layer has 1/8" gaps between sheets for expansion. When I apply the thinset, won't it fill in these gaps? It seems to me that the seams should be taped but nowhere have I seen reference to this. Should they be and what kind of tape?
For the tile layer, the entire perimeter will expansion joints but I am wondering about interior joints. My floor consists of a rectangle approx. 12' x 14' (the long edge runs east-west). Several arms branch off from that. On the North side (northeast corner) making a 2 foot wide connection to the main triangle is a 2'X12' branch running north along a living room wall. That leads through the living room to our front door. A second branch leads south off the south east corner to the back door. It is 4' x 10' and has a bathroom connecting to it on the side. The final branch leads east off the southeast corner and is 5' x 8'. I'm not sure you can follow my description but I hope so. Do I need joints at these branches or are they unnecessary? The Schluter site deals mostly with simple rectangles so I'm not sure how to apply their recommendations to my site.

Thank you,

Steve

Don't worry about the small gaps in the ply, the thinset will fill it up.

You only need an expansion joint if you have a 20-25' of continuous tile. Just leave your normal expansion joints along the perimeter, about 1/8-1/4".

As to the plywood gaps, this is a pretty common question, and it kinda makes sense. You could fill the plywood gaps with a cheap flexible caulk, I often do.

As to movement joints, if you need them, ditra doesnt get you off the hook. If the tiled areas dont get a lot of sun, you will probably be ok. You could as a precaution use a color matched caulk at the joints where these hallways etc meet the main room.:)

i use fiber board on top of the plywood..don't have to worry about the gaps

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