My Foyer Project - Wont end in divorce..... [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-02-2007, 08:34 PM
Here is what i have:
a small foyer, probaly 4X8. (sub is 3/4 ply). Structure is 2x6, 16 OC running the 5 feet width of course every 16 inches. I want to put nice 1/4 thick Sheldon slate down and i'm have some concerns about the subfloor. I checked the Deflecto and seems that i'm ok for stone since i imagine its such a small area and the way its built. I was hoping i could just put down some cement board (1/4 inch) with thinshet and screws and then lay the slate. I'm sure it can't be this easy. I'm so confused after reading all the posts.

Ok, please tell me where i'm wrong.. Do i need more ply then the cement board? Or, can i get a nice job with just the 1/4 cement board? It is a wicked small area really. And, the wife is already giving me the hairy eyeball on this project.....

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03-02-2007, 09:35 PM
I would add a second layer of ply and then use Ditra to keep the height down


03-03-2007, 01:18 PM
Welcome to the Forum.... :D

Got a first name that we may have? Put it in the UserCP above under edit signature..

The joist span is 5'?

since i imagine its such a small area

The size of the area isn't key - it's the joist structure... :)

03-04-2007, 06:51 PM
I should have been a little clearer. Since its a front foyer in a split the joists only run under the stairs up and stop at the stair going down. I 'm no builder but the space is open under the stairs so i climed under and measured the area. Good or bad the measurments are right, I hope its good though.

03-04-2007, 07:22 PM
Dark or Soda,
Like Jason said, you can add another 1/2" ply over the 3/4" for stone, and put either Ditra or 1/4" CBU, if you can tolerate the additional thickness.
The 3/4" ply should be good for ceramic tile putting 1/4" CBU over it... and as always - the more ply the better - to a point of course... :D

Another test you can do to make you feel better about the structure, is jump up and down on the ply and feel how much it moves...

03-04-2007, 07:30 PM
Unfortunetly anything more than 1/4 more (with all the extras) would put me at to thick of a treshold. I jumped on the floor like a circus pony and added an extra 1/4 ply. Floor feels very strong. Since i have good access to the sub, i could add brace support if needed? What can i expect for a finshed floor height with thinset>ditra>thinset>and 1/4 thick tiles? Can i stay near 5/8's? I'm buying some one a beer if the answer is good.....

03-04-2007, 08:40 PM
Welcome, Michael. :)

Unfortunately, you haven't really done any good with the addition of whatever 1/4" plywood you installed. Might even have set yourself back a step if it's a Luan-type. But for sure there is not likely to be anything in the local big-box stores or lumber yards that is a structural grade of plywood less than 3/8ths-inch nominal thickness.

Your joists are fine if, in fact, they really are properly supported with only a five-foot span (rather unusual). The problem, especially with a natural stone installation, is generally gonna be in the subflooring span between the joists.

You can install over what you have and take your chances, of course, but in a high-traffic area like an entry, I think you may be doing just that.

My opinion; worth price charged.

03-05-2007, 04:26 PM
Well i certianly would rather keep the floor for awhile. So, id like to add to the floor strength. Seems my issue turns into how i can gain strength without adding to the floor hight.

I could pull off the 1/4 ply and add 1/2 ply but my problem turns into thickness to the entry (and my head). Probally puts me in the doors path.

Do i have any other options here tha could keep the hight down?

Perhaps a nice area rug would look great.......

03-05-2007, 06:00 PM
Michael, better carpenter than a tiler, so I may be able to give a little DIY advice. The most important info here is your joist structure. 4x8 space but are the joists 8 ft or 4 ft. Will assume good condition and 16" oc. This gives you a possible 950, I think that was with the 5 ft you stated earlier versus 320 if 8 ft. Give it another look and pay particular attention to the span between supported ends. This is critical to your needs.

Also, if you have access, can you add a small header midspan if they are 8 ft.
I've reinforced many old joist structure (actually poorly conceived) with midspan headers below. Works great for midrise decks also.


03-05-2007, 06:13 PM

We need a deflecto test to determine if the structure will support ceramic or stone... Yours passed for both...
Next we need to determine whether the floors surface is rigid enough for stone or ceramic. Yours is not enough for stone..
3/4" ply will support ceramic with 1/4" CBU, but 3/4" ply and 1/4" ply and 1/4" CBU won't support stone - long term... :)
Back at me cx if'n I'm tellin tales.... :D

OH, Howdy Randy, Welcome...