Ceramic tile prep

[Cher69newbie]

I have 1 inch tongue and groove subfloor. What goes on next? 1/2 plywood? Then 1/4 hardie. When do you use leveler if needed?

[Shaklee3]

Hi Cherie, I'm not a pro but can echo the answers I hear on these forums. You need to make sure your deflection rating is strong enough for the tile you're using. Go here and plug in your joist height, span, etc:

https://www.johnbridge.com/vbulletin/deflecto.pl

You need a rating of L/360 for ceramic tile.

Once you've verified that, look at the condition of the wood, and look for any gashes/holes/etc. If you have any really bad spots you may need to pull that piece up.

Next, check for flatness. Your subfloor only had to be level, not flat. The larger the tile, the more this matters. I think the rule of thumb is something like no more than 1/8" difference over 10', but someone will correct me if I'm wrong. You can use SLC for leveling, but not all of them work on wood, and done of them require it to be applied very thick to get strength.

If you don't want the thickness, you can remove the subfloor and do things like plane the joists to get where you need to be.

Once that you're as flat as needed, you can do hardibacker, ditra, or numerous other products depending on your comfort level and budget. Uncoupling membranes like ditra are the easiest since they cut with a razor and are light, but they're also not cheap.

[cx]

First thing we'd need to know is the purpose of this additional subflooring. You are planning perhaps to install ceramic or stone tile over what you're constructing?

Cliff has you pointed in the right direction except I think he got his part backward:

Originally Posted by Cliff

Next, check for flatness. Your subfloor only had to be level, not flat.

If you're doing a tile installation, you need a flat substrate. The tiles care not a whit about level, only about flat. The larger the tiles, the more they care.

But let's start with the purpose of your floor improvement, shall we? And what you're starting with. You say you have "1 inch tongue and groove subfloor." That's T&G what? Sawn boards? Plywood? OSB? Other? And is it actually a full inch thick?

Then, of course the joist structure as Cliff pointed out.

This part of the project from your Overpricing thread?

[Shaklee3]

Thanks cx. That's what I get for responding by phone right after I wake up

[Cher69newbie]

Sorry, thought I had a picture here of floor.[ATTACH][/ATTACH]
Not sure if I did it correctly. Taking out 3 layers to sub. Long process.

[Cher69newbie]

Then will tile with merola attica gris. Almost 17 x 17 tile. No movements, squeaks in floor. I am going down to take measurements today of joists. I did have a contractor over to look when they put in a toilet in our laundry room and he said it was good for the weight of shower and tile. But I am going to measure it out myself.

[cx]

Originally Posted by Cherie

...he said it was good for the weight of shower and tile.

Most any residential structures are suitable for accommodating a great deal of weight, Cherie, but you're looking for the design deflection of the joist system under a standard loading (10 psf dead load, 40 psf live). Our Deflectometer in the dark blue bar near the top of the page is a bit more conservative than that and will give a good go/no-go reading to begin your evaluation.

But it would still be helpful to have some idea what you're doing. Is this just an empty space where you now plan to build a shower and tile the floor? Is this the same laundry room where you've installed the toilet? Are we on the ground floor with a crawl space below? Are we converting an attic space? Is that tub/shower looking thing in your photo in place or is that to be moved into the area in question? The more you tell us about the project, the better we can help you complete it successfully.

My opinion; worth price charged.

[Cher69newbie]

Most any residential structures are suitable for accommodating a great deal of weight, Cherie, but you're looking for the design deflection of the joist system under a standard loading (10 psf dead load, 40 psf live). Our Deflectometer in the dark blue bar near the top of the page is a bit more conservative than that and will give a good go/no-go reading to begin your evaluation.

Well we have a wonderful discussion between 2 results for deflection. 1. L/640, 0.188
2. L/1289, .060
While they argue discuss, I am going with it's good for ceramic tile.
RE Subfloor while I was down there I think I was mistaken about subfloor. There is the picture I took from up in the bathroom and I am attaching 1 looking up from basement/ crawlspace.
This is a 1st floor(each house) bathroom Reno. Removed shower and moving location of vanity and toilet by a foot.
Picture before demo.

[Cher69newbie]

Even looking through a cutout that we repaired after the shower tearout the 2 layers were not really noticed by myself and at least 4 other various people doing different work in bath and down there. The steam shower/jacuzzi is in the spot it will stay. The room is 10 ft x 6ft 3 in. The shower is 67 in. By 35 in.

[Cher69newbie]

Sorry, I did see a picture of the present bathroom so far

[Cher69newbie]

Originally Posted by Cher69newbie

Sorry, I did see a picture of the present bathroom so far

Progress on getting up black tar layers, and Purple power seems to be the best so far.

[Cher69newbie]

At what point should I apply leveler? After 3/4 plywood and b4 Ditra? Should I get a particular kind to use with ditra?
Almost there 4 more squares of linoleum, vinyl vinyl tiles and tar to get up. Decided on Ditra since ceramic tiles are almost 17x17.

[cx]

Cherie, there is no technical reason to level that floor. Your ceramic tiles care only that the floor is flat, they care not at all about level. But if you want to level it with some sort of SLC you would do that prior to installing your Ditra.

Originally Posted by Cherie

Decided on Ditra since ceramic tiles are almost 17x17.

Not sure I follow the reasoning there at all.

My opinion; worth price charged.

[Cher69newbie]

There are quite a few high points and alot of the edges are low or high. I'd rather not since the floor is level just has valleys and hills. I can see or feel. If course I am so used to feeling wood for smoothness that the woodworker in me needs it sanded and smooth. If I am incorrect I will ignore it. I do have a feeling it might be that. I am presently sanding down a rocking chair and repairing it.it might have carried over. Had to work on something calming when the tar stuff would frustrate me.
My husband thinks the T&G 3/4 plywood would take care of it. I would hate to be cracking tile. I switched because I am hoping Ditra would be easier for me to get under the monster. When I get to that point I am moving it tiling then waiting as long as needed to move it onto the done portion.

[ss3964spd]

Even if you did install the 3/4" ply you would want to reassess how flat the floor is after the 3/4" ply is installed, then apply SLC where needed.

Given the existing T&G floor, I'd use a long straight edge to find all the high spots, then assess if they can be reasonably flattened out by sanding without removing much material. Then I'd install 1/2" ply (you need ply over those sawn boards) and then check again with a long straight edge. Use a SLC to fill in the low spots. Cover it with Ditra after it's leveled.