Tile leveling clips - GIF

[Frank S]

Jon as you may remember I also used 2 layers of backer board and brick patterned tile as a thermal barrier behind our wood stove

[meyer77]

Cement board does not have any structural strength!

[Frank S]

Cement board does not have any structural strength!

Come over and jump up and down on the part of my kitchen floor that is slab then jump up and down on the section that has a wood sub floor blindfolded and tell me which is slab, and which has 2 layers of cement board under the tiles. Ordinarily I would agree with you. I also know that laying ceramic tile on a wood floor usually means a re-grout every 2 to 3 years its been about 6 years now and no re-grout has been required.

[meyer77]

A few questions:
1. What was the thickness of the wood sub floor,was it plywood or 1x6 t&g?
2. Was the cement board installed over thinset as per installation instructions and screws every 8"?
Just because you have not had any problems does not change the fact that cement board does not have a structural rating.
I have been a tile installer for over 50 years including 26 years of my own business in NJ.
99% of floor tile installations were over plywood. Several things needed to followed for a proper installation.
1, A minimum of 1 1/4" exterior grade plywood at least B rating for top layer, 2, spaced 1/8" between sheets, 3, cleaned of all contaminants ( drywall dust, construction adhesive drywall compound) screwed every 8".
4, Use of a plywood rated mortar adhesive (incorrectly called thinset, thinset is a method not an adhesive) not the 12-13 dollar home depot crap.
When I moved to WV I worked for a tile contractor, His method for tile floors was 1/4" durock over 3/4" sub floor glued with construction adhesive and screwed.
I didn't think that was the correct method but he was the boss not me.
I don't know what The current (2020) Tile Council of America hand book says the requirements are for setting tile over plywood, First I don't have a copy and do not intend to buy one ($50.00) as I have been retired for 4 years and don't need one.

[meyer77]

I have been a tile setter for over 50 years, second generation, son is third, have about 30 in family, cousins, uncles, brothers, nephews, in laws and son.
Cement board does not add any structural strength. Tile Council of America states a minimum of 1 1/4" subfloor 3/4+1/2".
About 95% of the jobs I did were over plywood (must use proper mortar adhesive latex modified) The good stuff is not cheap $48-50 a bag.
The floor was washed to remove spackle and dust then screwed every 8" all directions.
I have used the clips maybe once or twice setting tiles 24"x 24". That tile had a boarder of 8"x48" that were actually warped almost 3/16".
One job the woman of the house wanted 24"x24" on the ceiling! I said no way!
I did have a 9"x18"x5/8 come off the ceiling (10' high) and just graze my head, It still took 7 staples to close the wound.

[Frank S]

Back when I did the kitchen floor all I knew about the wood section of the floor was it had a layer of 3/4 ply over a plank subfloor.
When I removed the floor in the bathroom just behind the kitchen, I got a better idea of the construction the floor joists are rough cut true dimension 2x8 set on 12-inch centers over 4x10 beams on 8ft centers with 4x6 beams between them on 4 ft centers the main beams were supported every 10 feet initially I guess on tapered poured piers no idea how deep in the ground they go but they are about 12' in diameter at the top and close to 16" where they disappear into the ground apparently over time there had been some settling or warping of the 4x6 beams as several 16x16 x4" concrete pads had been placed with 8x8x16 solid concrete blocks on top of them then shimmed to the beams with cedar shingles. the subfloor planking is 1x6 true dimension T&G with the 3/4 ply over the top.
When I had installed the 2 layers of cement backer board under the tile in the kitchen, I used a premixed construction adhesive more like a thick glue than anything else I don't recall the brand but I remember going through several 2 1/2 gallon pails for the project. at somewhere around 40 to 50 bucks each the first layer of cement board is screwed down on the 200mmx200 mm or 8x8 grid the second layer is turned 90° to the first and the screw pattern is the same but offset so that every screw hit the center of the lower grid first layer is screwed down with 1 1/2" long screws and the second with mostly 2-inch-long screws. This is the only tiled floor I can remember that is never cold when you walk on it with bare feet in the winter either the portion over the slab or the portion over the wood floor. I don't know if this is because of having 2 layers of the cement board and 3 layers of adhesive that cancels the thermal conduction or what, but we are happy with it. The only thing I'd like to do would be to someday grind the grout down in the joints and insert brass strips but the color and texture of the tile we have wouldn't look right

[meyer77]

You never know what you will find when you start working on an old house.
My first was in NJ and built as a summer home for kids of the couple who lived next door. The living room must have been an add on after the bedroom bath because it did not have any footers only block laied in the ground! the kitchen (converted porch) floor was set on a 4x6 red wood beam.
When I decided to replace the slate patio (it was in bad shape) the main part was set on 4" on concrete but the outer perimeter had a 30"x30" concrete footer!
The contractor I hired to tear it out could not lift it with his backhoe! so he just dug a big hole and buried it.
They could have used that for the footers for the LR and kitchen.

[meyer77]

I did a job once where the field tiles 24"x24" and the border and base tiles were 8"x48". The 8x48 tiles were bowed 1/8" end to end, I had to screw a piece of wood to the wall then press down the other end and screw a second block of wood to hold down the end! The 8x48 would flex the 1/8".
I think the attached will be my last tile job (50+ years is enough)