[Bret86844]

Hello all! My wife and I are re-doing our kitchen. The house is from 1947 and we are pretty sure the kitchen is original. We will be pulling out the old vinyl flooring and putting down ceramic tile. The existing floor is 3/4" x 7.5" wood planks laid at a 45 degree, and 5/8" plywood on top of that.

We want to cut out the plywood. Our proposed new floor would be:
-3/4" x 7.5" planks
-1/2" backerboard
-this ceramic tile

Really what I'm asking is do you think the plank sub-floor is a good base for my tile? It seems plenty strong to me, but I'd like to get your thoughts.

For what it's worth the floor is supported by 1.5" x 9", set 18" on centers.

Here are photos of what I'm working with:

Sink area where the plywood subfloor was never installed:

Width of the sub-sub floor planks:

Thickness of plywood subfloor

Thickness of planks as measured from the basement below:

View of the kitchen floor construction from basement below:

Width of support joists:

Depth of support joists:

 

[joecaption]

Whats the span on those joist?
Not a great plan for a few reasons.
Tile board does not add any strength to the floor, 1/2" will do nothing but raise the floor, 1/4" is all you need.
That size tile requires a dead flat non flexing floor, not likely in an old house like that.
Why are you removing the plywood?
That's the only thing giving the floor any strength and giving you a flat surface to lay the tile board on.
That plywood needed to be nailed down down every 4" on the edges and from 6 to 8" in the field.
There needs to be thin set between the tile board and the plywood.

 

[JazMan]

No way! You must install min. ⅝" underlayment ply or OSB, then ¼" or ½" concrete backer or a membrane such as Ditra.

Jaz

 

[intelpcguy]

Don't cut the plywood

You need it, min 5/8" screwed to the joists, at least you have 2x10 floor joist. I have 2x8.

1x8 subflooring on a diagnol are not suitable support for any backerboard. My entire house is raised foundation, and as I go remodeling it room by room, I rip up old flooring ( the kitchen was 2 layers of sheet vinyl over 1/4" underlayment, the rest of the house is 3/8" t&G oak ) in each room, and I lay down 5/8" t & g plywood and screw the entire floor down with 3" deck screws over the joists, and 1 5/8" Hardinacker screw about 6" on center every where else.

This has totally eliminated any creaking of the floor before setting the flooring underlayment ( 1/4" Hardibacker in the kitchen ). I did my kitchen hardibacker wall to wall before setting cabinets. I have the flooring installed for 5 years with no cracking of tiles or grout joints.

 

[Bret86844]

Whats the span on those joist?
Not a great plan for a few reasons.
Tile board does not add any strength to the floor, 1/2" will do nothing but raise the floor, 1/4" is all you need.
That size tile requires a dead flat non flexing floor, not likely in an old house like that.
Why are you removing the plywood?
That's the only thing giving the floor any strength and giving you a flat surface to lay the tile board on.
That plywood needed to be nailed down down every 4" on the edges and from 6 to 8" in the field.
There needs to be thin set between the tile board and the plywood.

Span is 18". The reason for removing the plywood would be so the final installed height would match the adjacent rooms. A proper subfloor takes precedent though.

Based on your's and the other responses it looks like the plywood is going to stay. I will just fill in the gaps with new plywood.

Related to the subfloor, there is one spot that creaks. Would adding additional screws down through the planks below take care of this? A nail or two has worked its way loose over the years.

 

[Bret86844]

Whats the span on those joist?

Just realized you may have been talking about the long dimension, it's between 11 and 12'.

 

[JazMan]

Right. 18" is the spacing not the span. I wonder why 18", should be 16" o.c. or less.

Jaz

 

[Bret86844]

Right. 18" is the spacing not the span. I wonder why 18", should be 16" o.c. or less.

Jaz

I will double check but I'm almost positive it's 18". It's a 1947 house so maybe that has something to do with it?

 

[JazMan]

No, the norm has been 16" on center for ever. Maybe you measured from the beginning of one to the end of the next and not center to center. Also sometimes someone spreads a few further because of odd length left. Should be 16" oc which means 14.5" of empty space between the joists.

Jaz

 

[ktl5005]

Doing a remodel in my bathroom. 2x8, joists with 3/4" plank subfloor. I added 19/32 exposure 1 pine plywood, and am using membrane DITRA. Keeps height differences lower and also with the ply it is following the directions of the DITRA for install.

 

[Bret86844]

Doing a remodel in my bathroom. 2x8, joists with 3/4" plank subfloor. I added 19/32 exposure 1 pine plywood, and am using membrane DITRA. Keeps height differences lower and also with the ply it is following the directions of the DITRA for install.

We are considering using Ditra. Originally we were thinking about Hardie board because we thought it would increase the rigidity of the floor. But from what I'm learning, it provides zero structural support. Since Ditra is flatter, this is preferred. Have you put it down yet? I'm curious what you think of it.

 

[ktl5005]

We are considering using Ditra. Originally we were thinking about Hardie board because we thought it would increase the rigidity of the floor. But from what I'm learning, it provides zero structural support. Since Ditra is flatter, this is preferred. Have you put it down yet? I'm curious what you think of it.

I have not put it down yet as I am awaiting arrival of my bath tub and install that first. From what I read your floor just needs to be flat without "waves" in the subfloor. You can use a 2x4 to add pressure to the DITRA to get it to bond properly to the modified thin set. DITRA call for 15/32 (1/2" nom) over plank subfloor, but i went with 19/32 for a little added thickness. You can follow my remodel thread here, and as you can see have some picture of the demo up already....
http://www.diychatroom.com/f84/porcelain-tile-bathroom-remodel-joists-acceptable-372729/