[DiYerInNY]

Redoing tiling on bathroom but noticed that bathroom is half concrete slab and half wood. Concrete slab is from the original construction of the house and wood subfloor was added when we hired some handyman to expand the bathroom.

The previous handyman laid a thick coat of thin set and set the tile directly.

Planned on laying Ditra this time around when new porcelain tile but not sure if I should lay plywood on top of the wood and concrete slab to make it 1 material.

Or should I pour self leveling compound on wood then apply the Ditra ?

 

[carpdad]

Not a pro. This is a guess only. I would want to transition slab and wood with one kind. As such, plastic vapor barrier or redguard the slab first then screw down half inch ply over the transition. No glue and screw into the wood subfloor, not into joists. Use tapcon screws for slab part. Then redguard this new underlayment then schuluter system or 1/4" cement board. I redguard cement boards also before tile and thinset. I read 3-4" screw spans for the underlayment edges and around 6" in the field. I'd assume the same for slab part, maybe more depending on how well tapcon screws seem to grab. Predrill and countersink for all screws. For wood, there is drill/countersink bit. For slab part, predrill a hole little larger than the screw for the plywood part and drill into the concrete. Vacuum out the dust before screws.

 

[DiYerInNY]

Not a pro. This is a guess only. I would want to transition slab and wood with one kind. As such, plastic vapor barrier or redguard the slab first then screw down half inch ply over the transition. No glue and screw into the wood subfloor, not into joists. Use tapcon screws for slab part. Then redguard this new underlayment then schuluter system or 1/4" cement board. I redguard cement boards also before tile and thinset. I read 3-4" screw spans for the underlayment edges and around 6" in the field. I'd assume the same for slab part, maybe more depending on how well tapcon screws seem to grab. Predrill and countersink for all screws. For wood, there is drill/countersink bit. For slab part, predrill a hole little larger than the screw for the plywood part and drill into the concrete. Vacuum out the dust before screws.

Thanks for the reply.

I was actually leaning towards this, to put plywood over the concrete/wood subfloor. However in another forum, some one mentioned that this wasn't a good idea I was better off putting Ditra across the 2 substrates.

 

[Nealtw]

Was there a problem with what was there before? If not just do the same.

 

[DiYerInNY]

Was there a problem with what was there before? If not just do the same.

well the previous installation was ceramic tiling, and i plan to change it to porcelain tile ( 12 x 24 )

the ceramic tiles were set on top of a thick coat of thinset mortar ( about 3 inches worth ) on top of the concrete/plywood substrates.

tiles within the transition line where the concrete and plywood, would pop off and had to stick it back on about 2 times.

since i'm using a 12x24 staggered, i'm wondering if it would be ok to set the tile on top of the transition line with Ditra+plywood underlayment

 

[Nealtw]

well the previous installation was ceramic tiling, and i plan to change it to porcelain tile ( 12 x 24 )

the ceramic tiles were set on top of a thick coat of thinset mortar ( about 3 inches worth ) on top of the concrete/plywood substrates.

tiles within the transition line where the concrete and plywood, would pop off and had to stick it back on about 2 times.

since i'm using a 12x24 staggered, i'm wondering if it would be ok to set the tile on top of the transition line with Ditra+plywood underlayment

What do you think of a grout line right above that joint in case there is some movement?

 

[DiYerInNY]

well the previous installation was ceramic tiling, and i plan to change it to porcelain tile ( 12 x 24 )

the ceramic tiles were set on top of a thick coat of thinset mortar ( about 3 inches worth ) on top of the concrete/plywood substrates.

tiles within the transition line where the concrete and plywood, would pop off and had to stick it back on about 2 times.

since i'm using a 12x24 staggered, i'm wondering if it would be ok to set the tile on top of the transition line with Ditra+plywood underlayment

What do you think of a grout line right above that joint in case there is some movement?

Not sure if I understand your question.
Are you asking what is my plan ?
I read that I should use a control joint and use caulking instead of grout .. although I’m not sure how I would go about doing that since I plan to do a staggered formation. Unless I caulk the tiles that are within the joint line between the wood/concrete

 

[Nealtw]

Not sure if I understand your question.
Are you asking what is my plan ?
I read that I should use a control joint and use caulking instead of grout .. although I’m not sure how I would go about doing that since I plan to do a staggered formation. Unless I caulk the tiles that are within the joint line between the wood/concrete

It won't help with staggered grout lines.:wink2:

 

[DiYerInNY]

It won't help with staggered grout lines.:wink2:

what do you suggest i do then?

 

[Nealtw]

what do you suggest i do then?

I have never seen it done so a guess would be the best I could do and the grout line was the best I had.

 

[carpdad]

3" cement you removed probably was not thinset. It is called drymix bed and it is more like a mortar bed that was mixed to drier consistency. Before the separation sheets, all tile bedding was done like it. If you have that much room, there are more possible ways, and the main factor would be removing two separate movements from the finish tile as much as possible.


Again I'm guessing here. Never have tiled over such a structure.


How about 2 sheets of 3/4" exterior grade plywood? Don't fasten them to slab or wood floor. Search floating subfloor. Find flat plywood or you try to make them flat by sandwiching the curve against curve. First lay the plywood loose with 1/8" space. Then overlap the joints by at least 2' or so and screw them together. Maybe glue in between as well. Over this, redguard or vapor barrier and then use shuluter floor system or 1/4 or half inch cement board.


You may want to separate the floor from wall and use pvc trim along the base. PVC can be painted.



Or shuluter floor first over slab and wood, then build a thick drymix bed over. Use modified (meaning a bit more flexible) thinset for the tiles and mix the grout with acrylic mix liquid than using water. The admix will be more sticky and dry out faster. I had to grout in small areas and clean up quickly. The admix grout will be bit more flexible. After a couple days of drying, seal again. I wouldn't use epoxy grout here since it's good for stain resistance but probably not tolerating movement.


BTW, the forum also has separate section for tiling. There are other forums as well. Search for tile or floor forums. Just remembered, john bridges forum.

 

[udraft]

It's fine to use the wood as a spacer, you'll want the tile on a cementatious surface.
If practical create a joint (3/16" or so) at the transition, scrape or cut the joint (grout) out and caulk it with something that has a bit of movement.
As an alternative you might try a 3" mortar bed with metal mesh reinforcement. The old method, rarely used. Normally the mix would just be masonry cement and sand (4:1?), but I wonder if you couldn't use something lighter. A lost art really, basically you run a screed line on the perimeter, then work towards the center. Install/float the entire floor so you get the right slope, then work off boards to install the tile.

 

[DiYerInNY]

It's fine to use the wood as a spacer, you'll want the tile on a cementatious surface.
If practical create a joint (3/16" or so) at the transition, scrape or cut the joint (grout) out and caulk it with something that has a bit of movement.
As an alternative you might try a 3" mortar bed with metal mesh reinforcement. The old method, rarely used. Normally the mix would just be masonry cement and sand (4:1?), but I wonder if you couldn't use something lighter. A lost art really, basically you run a screed line on the perimeter, then work towards the center. Install/float the entire floor so you get the right slope, then work off boards to install the tile.

yea i was considering making a mortar bed but thats what the previously installer did. however if i'm being honest, im not sure if i have that much confidence making it perfectly level therefore would prefer to use plywood