Tile over old hardwood subfloor?

[4ddiction]

Hey few questions. What would be the best way to put down some tile over a hardwood subfloor. House was built 1917 northeast, I believe balloon style structure. The 7/8 hardwoods were run throughout the entire first floor then the walls were put ontop. I wanted to use Ditra and porcelain tile. However I want to keep the transition between kitchen (currently has floating vinyl flooring covering up damaged hardwood) and dining room (original hardwood floor) as small as possible. I know Ditra doesn’t recommend putting ontop of hardwood.

Should I put down a 1/2 plywood over the hardwood or should I cut out the old subfloor In the areas that will be tiled and lay new subfloor down to the joists.

Any advise would be great!

Pics from the basement

[cx]

Welcome, Connor.

Is the wood floor you're showing us from below the only layer of flooring in the area to be tiled?

If so, your only option, according to the ceramic tile industry, is to put a layer of minimum nominal 1/2-inch, exterior glue plywood with no face of grade lower than C. On top of all that you can install the tile substrate of your choice.

Have you evaluated your joist structure to determine if it qualifies for a ceramic tile installation?

My opinion; worth price charged.

[e3]

Sand it and Finish it, looks nice !

[4ddiction]

It is the floor from the basement view. Which is the subfloor. I would love to refinish them but the previous owner put down the tile and vinyl floor over areas because the top of the said floors could not be refinished. Too much damage.

The joists are original 2x8 actual size. I believe the spans will handle the deflection.

[PC7060]

Originally Posted by Connor

The joists are original 2x8 actual size. I believe the spans will handle the deflection.

Have you measured the joist span and run the deflection numbers using the Deflecto tool in the blue menu bar at top? Best to be sure.

[jadnashua]

To screw down a layer of plywood over oak will mean probably drilling pilot holes, and that means lots of them, then screwing it down will still be a pain! Oak, especially old oak, is pretty tough, and a pain to drill or screw into.

To keep the height down, you'd probably want to consider cutting out the oak, putting in some blocking where required, then installing a new plywood subfloor. Well, put in the blocking prior to cutting the oak out...

[4ddiction]

Hey so do I count the span of the joists from foundation to foundation? Or from foundation to my center beam that runs in the middle of the house. The joists are full length. 21’ from foundation to foundation and 10.5’ to the center main beam.

If I were to rip out the hardwood and sister joints to allow for the old pieces of the hardwood to rest on would require even more work moving electrical cables.

[jadnashua]

A support beam counts as a beginning/end of a span. The calculator is based on the distance (span) between supports.

If your support beam is in the middle of your tiled area, you may have two different spans to calculate.

[4ddiction]

The tiled area (kitchen) is between the center main beam and a foundation wall. So that span is 10.5’, with 2x8 joists on 16” center I believe I am in the clear then.

[PC7060]

Not to quibble but that floor looks like Southern yellow pine or similar. Splitting may still be an issue as jadnashua mentioned but not nearly as much as oak would present.

[jadnashua]

Yeah...that's pine underneath...so is there oak on top of it? Seem to remember that's what was said.

Pull off the oak, put a layer of ply down.

[4ddiction]

Not sure what wood the hardwoods are made up of. Since they run the whole span of the house. Would it bring the structural integrity down by cutting out sections of it? The hardwood floor under the wall would still be there. Of course I’d replace it with a 3/4 subfloor

[cx]

Originally Posted by CX, Post #2

Is the wood floor you're showing us from below the only layer of flooring in the area to be tiled?

I'm still not clear on this.

[4ddiction]

Originally Posted by CX

I'm still not clear on this.

Yeah that wood is the only wood ontop of the joists.

Here is a picture of below the kitchen, area in question

[jadnashua]

Deflection consists of two components:
- along the joists determined by the species, thickness, and height of the joist and the span
- in between the joists made up by the subflooring

Both components need to be suitable for the type of tile you select (ceramic or natural stone).

Dealing with subflooring doesn't result in changing the along the joist strength.

Those planks, along with a second layer of plywood is usually good enough for tile.

Along the joists, I haven't run your numbers, but maybe not.

Two layers of good plywood would be more stable than the planks and a layer of ply on top. Solid planks just move too much between seasons as the humidity levels change, so you need ply on top that isn't as affected by that.