I'm in the process of renovating my kitchen. I bought enough tile to cover my kicthen floor and the staircase landing for basement stairs/side door. I'm concerned about the strength of the landing. It was contructed with 2x4 framing, 16 OC, with 3/4" oak flooring. There is no subfloor, just finshed tongue and grove flooring. There is about 3/4" gap from the floor to the bottom of the door. The landing is 36x36.

My plan is to rip out the existing hardwood floor and add sister joists from 2x4 studs, making them 3-4" OC. Then, I will glue and screw 1/2 plywood on top. I plan to use 1/4 hardi backer for tile base.

Do you think this will be strong enough? I know everyone on this forum says minimum subfloor must be 1-1/4 thick but I can't do it in the case as the bottom of the door will hit. I think 2x4 joists, 3-4" OC will add a lot more strength than another layer of plywood. Please let me know what you think. Thanks.

 

What type of tile are you wanting to install? Ceramic, porcelain, natural stone?

If it's ceramic, you will want a 5/8" ply subfloor, and if natural stone, at least 1 1/4" thick.

Anything less then the above specs you would be taking a chance. The tile installation could last a long time, or it could not.

Seeing that you are worried about height issues, you could look into Schluter Ditra underlayment, which is only 1/8" thick. This would replace the need for a cement board.

 

The tile is porcelain and is 3/8" thick. I have exactly 1-1/2" from the top of the floor joists to the bottom of the door. I could use Ditra but not too sure if it's going to give me much more space. I was plannning on screwing down the 1/4" cement board and not thinsetting it to the plywood.

I finished framing last night and have to say the 1/2" ply is not very sturdy (didn't screw and glue yet). I was thinking of using 3/4" ply and just thinset the tiles directly to the ply. I found a product called one-step that can bond tiles directly to plywood w/o cement board or ditra, or at least it's was the manufacturer claims. I know this is not the preferred method but I'm kinda stuck in a jam. I figure since the area is only 3 x 3, if the job fails, I can always rip everything up and start over.

 

jason

I cant see your step and landing framing, and having a hard time envisioning exactly what you have. What I will tell you is that it has to be rock solid, no movement. After you take up the hardwood, do whatever you have to to reinforce the landing so that you have no movement.

As to your subfloor/underlayment/tile situation, you say you have 1 1/2" to work with. That should be plenty. 3/4" plywood, 1/4" cement board and tile will be more than sufficient if the framing is up to par.

Some things you need to know.

Dont use 1/2" plywood, use 3/4".

Dont set tile directly to plywood, use cement board or an isolation membrane over the plywood first. I know there are thinsets that say they can be used over plywood, but that method should be avoided.

Dont install cement board without bedding it in a fresh bed of thinset. If you dont use thinset here, there will be voids between the plywood and the cement board that will cause movement and could cause tile failure.

This isnt a complicated job here and there is no reason you should approach it this way. Do it right and do it just once.

 

HeresJohnny, space is my main concern. I will not have enough space for 3/4" ply, thinset, cement board, thinset, and tile. If I do it this way, it will be close to 1-3/4" thick. Rememeber, I only have 1-1/2" from framing to bottom of door.

The framing is such: 2x4 constrcution, 4" O.C. and total space:36" x 36".

 

jason

It wont be 1 3/4". I think you may be assuming that if you use a 1/4" notch trowel for your thinset that it will take up that much space. Not the case. If you use 1/4" notch under your 1/4" cement board the total height will be just under 3/8". Typically (if there is such a thing), the height added by the trowel will be a little less than 1/2 the height of the trowel.

At a minimum, you should use 5/8" plywood, dont use 1/2". You can save a lot of height by using ditra. The total height of ditra installed will be just barely more than 1/8". Just trying to reinforce the fact that you have plenty of room to do it right and not have to worry about failure.

 

Johnny

You are right - I was under the assumption that each layer of thinset will add 1/4" of hieght. I have to find Ditra - everyone on this forum swears by it. I asked my local tile store and he doesn't carry it - said to use one step or cement board.

My question now is how thick will the following combinations be:

1) 3/4 ply + thinset + 1/4" cement board + thinset + 3/8 porcelain tile.

2) 3/4 ply + thinset + Ditra (regular, NOT XL) + thinset + 3/8 porcelain tile.

 

Depends on the size trowel you use for the tile? I know the thickness, but what size is the tile? This may be a little more than the 1 1/2" you have.

Again depends on trowel size for the tile. This might work.

Just so you know, you can get away with 5/8" plywood and ditra. This will definetly work.

HD sells ditra. You can also buy it at most tile supply houses and online.

 

The tile is porcelain and is 3/8 thick. What trowel size do you recommend? I was going to use 1/4".

I didn't know HD sells Ditra, have to llok again. I went on their sites and found several local tile store sell it.

Thanks for the advice - will let you know how I make out.

 

What size are the tiles 12" x 12"?

 

Yes, tiles are 12 x 12 sqaures.

 

You could start out with 1/4" square notch trowel and see if you get full coverage. If not, move up to a larger trowel 1/4x3/8x1/4 square notch.

Lets see, I still have 52 seconds left to say something. So what else do I want to say? Nothing so I hope 52 seconds has passed.

 

I'm going to use 5/8 ply subfloor and either Ditra or 1/4 Hardi depending on clearance with the bottom of the door.

I'm also tiling my kitchen and plan to use 1/4 hardi for that room. I'm researching the recommended mortars for each product. The surfaces will both be plywood subfloor and porcelain tiles.

Ditra recommended:
subfloor to Ditra - modified thinset - polymer based (HD Flexbond or Versabond)
Ditra to tile - unmodified thinset - cheap stuff (HD CustomBlend)

James Hardi recommended:
subfloor to Hardi - unmodified thinset - cheap stuff (HD CustomBlend)
Hardi to tile - modified thinset - polymer based (HD Flexbond or Versabond)

I'm confused why they are in reverse. I understand the issue with polymer based thinset and the increased drying time and the requirement for a moist environment for a solid bond. But, I don't understand why they are reversed. John, can you confirm I selected the right mortars?

 

You got it right.

Ditra gets bonded to the plywood with modified thinset.

Dryset (unmodified) doesnt bond well to plywood. The thinset is not used to bond the hardi to the plywood, its function is to fill all gaps and voids between the two materials. The Hardi gets mechanically fastened to the plywood with screws and nails.

Ditra requires unmodified for all tile. The biggest reason for this is that ditra is waterproof and modified thinsets need air to cure. Modified thinsets used over ditra will cure from the edges of the tile in and it will take a long time for the thinset under the middle of the tile to cure. When grouted, it will take even longer. Dryset doesnt need air to cure so it will cure quickly when used with ditra.

Hardi is not waterproof so it will remove some of the moisture from the thinset and also allow air flow for the modified thinset to cure.

Its a little more technical than that but hopefully you get the idea.

I would not use customblend as a setting material over ditra. Its cheap low end garbage. Use a better quality dryset mortar with ditra. Customblend however would be fine under your hardibacker.

 

Thanks for info - looks like I got it right . I will get to work now - and let you know the outcome. Thanks for the awesome advice.

 

I finished the landing. The 5/8 ply plus 1/4 hardi worked great. There was no movement in the subfloor at all. I also added additional floor joists to strenghten everything.

I walked on the tiles several times and it's solid. No cracks or movement. Thanks for the advice!

 

Jason

Glad to hear the landing worked out good.

Why you walking on the tile, you trying to break it? Now get back to work. You have a whole kitchen to finish.