Howdy all,

Over the course of my childhood, I probably helped my father tile over a hundred floors. When doing a wood floor(which was admittedly rare in Florida), we ran over the wood after fastening it properly (fastener every square foot or less, depending on the thickness of the floor).

Those were the old days. I've done a few tile jobs over wood subfloor for my own use, and don't remember any self-destructing grout lines or cracked tiles, but after reading up for my next job(my kitchen), since it gets you buying a lot more, the books don't entertain the thought of tiling sans backerboard.

I'm on a financial budget and just as importantly a time restriction. This doesn't mean that I don't care how my floor comes out though. I'll do what I have to do to make the floor last, but I'm asking for your opinion:

A kitchen with two sheets of 19x32 ply setting on 2x10 floor joists spaced 16 OC. Plywood is fastened on joists with countersunk screws into joists(3") then a 1 foot grid of 1 5/8" screws.

In your opinion, am I OK to tile over this? Floor is solid with no bounces or squeaks.

Your thoughts are appreciated.

thanks,
json

"In your opinion, am I ok to tile over this? " Sure if you are using vinyl tile. However, I suspect you mean ceramic or porcelein tile rather than just tile. Two sheets of 1/2" ply just aren't enough for ceramic. Test your floor by getting on a step ladder in the basement and out your hands on the joists. Have about 5 friends walk and jump around in your kitchen and you will feel movement. Tile does not like movement plus we don't know the length of your joists or if the ply was glued too. I do a lots of this work and recommend 1/2" Hardibacker or cement board glued and screwed every 8" in all directions. I use a acrylic modified thinset mortar and special Hardi screws that self tap and self seat.

Hi there, and thanks very much for your reply!

During my two days of dwelling on this conundrum, I came to the decision to use the hardibacker, but I have a couple of questions for you, if I may, since No two sources(including your post) can agree with each other. I realize that it can be done more than one way, but would like your opinion.

1) Hardibacker's instructions on the site and in their product pamphlet suggest 1/4" for the floor, although you and some other sources suggest 1/2" Everyone seems to agree on thinset between the backer and subfloor then screwing it with the proper fasteners. I will tell you that there is a small chance that I won't be able to open my kitchen door if I use 1/2" board :)

2) seams: Hardibacker suggests 1/8" gap between boards with the same thinset used between the backer and floor to be used in the gaps, also using mesh tape. What do you think about this? I worry that the thinset & mesh tape is going to give me too much of a hump to deal with when tiling over.

3) For future consideration, it's a ten foot span and the subfloor is screwed only, no glue in between.

Thanks,
Json

#1 I use 1/4 for wall tiling and 1/2" for floors. I was sure thats what James Hardy recommended when he first made Hardibacker. Trim the door if you need to, there will be another 3/8 with the thinset and tile.
#2 Allow the 1/8 gap, the thinset ans mesh will sit almost flush when you strike the seam with a flat trowel. When you lay down your thinset for the tile the seam will totally disappear.
#3 No glue between the ply means using Hardibacker for sure in my book. Use Hardi screws found right next to the board in the store, 1 5/8" for 1/2 subfloor.

Have fun, this is not too difficult to do. Laying tile properly is a touch harder.

One more question :)

when you state 1/2 subfloor, do you mean per ply?

I've got 1 1/4 subfloor(19/32 X 2). Do I need longer screws?

thanks,
json

Right, I understood your post. You have two sheets of 1/2" plywood screwed but not glued to 2x10 joists, 16 on center 10" span. When you screw the Hardibacker down, with thinset as glue, your screw needs to penetrate the backer and a bit more than an inch into the subfloor and joist. The screw will penetrate about 1 1/4" into the sub floor when you drive home the 1 5/8" hardi screw. When I said "Use Hardi screws found right next to the board in the store, 1 5/8" for 1/2 subfloor." I was refering to the 1/2" Hardibacker subfloor.

"

Sorry, I misunderstood your post. Thanks very much for all your help!

Thanks,
Json