Subfloor Questions

So I am starting to remove the old floor in my kitchen and after some work I finally got down to the subfloor. It turns out that the subfloor I have is 19/32 plywood which im not sure is enough to lay tile on. So what are my options. I want to have at least 3/4" subfloor for this project and with the space avaliable that would be ideal.

So what are my options? Can I lay 1/4" ply on top of the existing subfloor and then the 1/4" hardiboard then the 13x13 tiles?

Or should I remove the subfloor and start over? Im not sure what I should do so any help would be appreciated.

 

Does your floor creek or bounce? If not, save your money and put the tile on the 1/2" ply.

 

I've been putting in floors for 15 years. If you're current floor is flat, then there is nothing wrong with going over it with another layer of wood, then your backer board, then tile.

Just remember, that is a good bit of height and the floors that it connects to will likely be lower. You'll have to have to install a transition threshold in the doorways.


If you have a nice budget to do it, then yank that old stuff up and redo it all. It would look better in the end.

 

what are your floor joists spaced at? What size are the joists?

 

Do it right the first time. Put down cement backer board otherwise you risk cracking tiles over time. If you crack one tile its almost easier to replace the entire floor than to get that one up.

 

Lay another layer of 1/2" ply at 90* to the original layer , glued and screwed into the joists .

If this is not an option due to height restrictions look into Schluter Ditra

http://www.schluter.com/6_1_ditra.aspx

 

Hold on I had a tape measure malfunction or operator error. I have 19/32" subfloors

The joists are about 7 1/8 x 1 1/2" and 16" on center

The house is about 30 years old.

 

Make sure the existing subfloor material is still sound. (no water damage or soft spots, etc.) You can cut those out and replace if just a small area.
Locate any squeaks in the existing subfloor and add deck screws to eliminate.

If subfloor plywood is butted (square edged) then all edges should be supported.
This means blocking between the joists if your existing subfloor (8' side) is not tongue and groove. We usually apply flat 2x4 blocking between the joists to stiffen and unify the butt joints
Use construction adhesive with any added blocking. A partner above with a screw gun is helpful when adding this type of blocking.

Be sure to apply your cement board according to mfr's instructions.
I like Durock's requirement of using adhesive between the cement board and the wood subfloor. This will not only adhere but will bridge any gaps as well.

Good luck.

 

Schluter Ditra

 

Good info, I've got a tile job coming up and I think this stuff is perfect!

 

Ok so I did a little more measuring and I could add an additional 3/8" plywood to bring the 19/32" subfloor up to 1" which seams like the ideal number. Thoughts comments? Best way to attach if this is a satisfactory approach. The existing subfloor has butted joints.

If I went this route then I would thinset and 1/4 hardiboards as reccommended.

 

Butted on the long axis ? You sure it's not t+g ? If not block as per jflan's post above .

I already posted how to laminate another layer of plywood .

Or Schluter Ditra , seriously .

 

I have 3/4" plywood and then 1/2" hardyboard then tile.

 

I have 3/4" ply , 1 1/2" of concrete , 1/4" Schluter Ditra then tile .

Do I win ?

 

the ditra looks like some pretty cool stuff.

I will get back to you about the t&g after it has been completely removed I have just ripped up a few smaller sections. Do you think adding 3/8" glued and screwed would be sufficient? Also How far apart would you place the screws and what type of screws do you reccomend?

 

I used the Schluter Ditra mat in my Kitchen. Due to height issues I couldn't use the hardi board plus it's a waterproof seal. It's not cheap but effective.

 

The main thing is to get screws through both layers and into the joists , this will stiffen up the whole assembly , so in that case 2 1/2" screws are long enough , in between the joists , I would go with shorter screws because you would just be laminating the two sheets together , 1 1/4 - 1 1/2" would work .

Is the underside of the floor system accessible ?

 

Yes the underfloor is accessible.

A side question have you used the schluter ditra over 5/8" plywood. How did it hold up. The ditra looks like it would be pretty easy to install with minimal extra effort.

 

I always frame floors with 3/4" ply , but the Ditra is designed for 5/8" ply and up .

If the underside of the floor is accessible and not receiving a finish ( drywall ) a simple " T " brace or even a 2x4 strap on the flat will stiffen the floor and reduce independent joist movement .

If the underside of the floor is to be finished a series of blocking is pretty effective too .

 

OP, how large is this area that you want to tile ?