backbuttering [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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10-16-2004, 10:23 PM
Bonjour Experts,

I'm new at tiling. After I applied the thinset on the floor with a 3/8" notched trowel, I was wondering if it is recommended to backbutter your tiles, resulting a double layer of thinsets with a total of 3/4" thick I'm laying porcelain tiles (12x12) on a plywood substrate.


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10-16-2004, 11:05 PM
Welcome, Tayo. :)

Please refrain from sayin' bonjour and such other words on accounta now John Bridge will be on here tryin' to show off his French speakin' abilities.

And it won't be pretty. :D

The short answer is no, you don't wanna be ending up with that much thinset under the tile, but backbuttering or "burning in" thinset on the back of the tiles is frequently recommended by big-time tile guys here. But all you want to do is make sure some thinset has been forced onto the back of the tile with the flat side of the trowel to ensure it wants to stick to the thinset on the floor.

But first let's discuss your setting these tiles directly onto a plywood subfloor. It can be done, mind you, but your floor must meet some serious and very specific installation criteria. So......without any prompting, how about you describe your floor, beginning with the size, spacing, and unsupported span of the joists, and ending with the type, thickness, and method of installation of any and all layers of subflooring.

My opinion; worth price charged.

10-17-2004, 12:10 AM
Hi CX,

I didn't know that John Bridge speaks French. Where I come from it's 50/50 frenchies. :D

I've read that backbuttering tile was a technique for newbies who want at least a 95% coverage of the tiles, to ensure the tile is properly set with the adhesive. Some professional say it allows for the grout to go deeper and gives a better floor contraction (whatever that means). Others say it's recommended for tiles of class 4-5 which are ceramic and porcelain..

Anywho, to answer your question I'm laying tiles in my 700-foot squared bachelor basement (I know I know... it's gonna be freakin' damn cold during our Canadian winter). From what I know, the house came with finished floor (2" wide) on top of a subfloor (1/2"). Since the floor is still in good condition, we decided to lay a cheap plywood of 3/8" thick as a substrate, screwed (1 3/8" long) at every 6". (yep.. that's a lot of screws).

At this point the floor looks very even, squeakless and ready to be tiled. Then, I decided to lay some tiles in my bedroom (100 feet sq)for a tryout, with backbuttering. It looks very handsome after I did the grout. It took me a heck of a time and a lot of mortar and grout to do this... prescisely 2 1/2 bags of thinset (22kilos each) and 2 buckets of grout (4kg each), that is because I used those 1/4" spacers.

Now I don't know if I should continue the rest of my basement with the backbuttering method. :twitch: it's tiring and moreover it uses up a lot of mortar and grout. Somehow, I'm wondering if I'm not overdoing this job..

It's now October... I better finish this before Winter... :loaded:



10-17-2004, 06:21 AM
Cx isn't gonna like your project so far, i don't think. He doesn't recommend screwing into the floor joists,your screws are too long,and he wants to know the type and spacing of your floor joists, since that's where all the support really is,other than that it sounds pretty stable,you are using modified thinset?Don't get too excited about John's French, i haven't heard it but from CX's description,my guess is it's mostly a lot of Wee,Wee and Frommage! :p :D

10-17-2004, 07:06 AM
It's getting better Dave. Why just the other day I heard him say cabernet sauvignon.

Hi Tayo, welcome to the Forum.

CX should be back later on with a continuance of his tirade :complain: about laying tile directly over cheap plywood...and it won't be pretty. I'll be standing by off-stage just in case you need a translator. Like mosta' them Texan's, he talk funny and you gonna need a real Yankee to hep you out wift the lingo.

10-17-2004, 08:36 AM
Hey! Ain't nothin' wrong with my Inglish. :mad:

Na, Tayo, ol' JB actually learnt to speak the Frog language when he was a wee lad inna Army over yonder to their land. Says he hablas it pretty good, but I can't tell on accounta I don't habla that a-tall. :D

Now, about this floor. You say it's a basement. Was not this basement constructed initally with a poured concrete slab floor? If so, tell us how the original wood floor "(2" wide) on top of a subfloor (1/2")" was installed. Was the 1/2" subfloor glued to the concrete? Did they lay down 2x "sleepers" on top of the concrete and nail the subfloor to that? Was the wood flooring nailed into the subflooring? The sleepers? Glued down?

Give more hints. Cut a hole in the floor if you must to determine what you have.

You might get away with tiling directly to the plywood as your substrate, but I'm certainly not gonna recommend it with what you have, or may have beneath it. Your attachment of the 3/8ths ply might be OK (not sure what Davestone calculated, but looks to me like you're just fastened into the old flooring and just a tad into the old subflooring), but I think you need a membrane (such as Ditra) or CBU on top of it for the tiling substrate.

We have a member who tiles successfully over plywood alla time, but he's real particular about the subfloor construction and type of thinset. Let's see what he thinks of your chances.

But first, tell us more about the floor structure.

My opinion; worth price charged.

10-17-2004, 09:11 AM
Lol, you guys are funny,

It looks like there's something else going on beside my problem in this forum between CX, Mike, and that old JB.

To answer your question CX, i'm gonna inspect my basement floor tonight.


10-17-2004, 09:22 AM
13/8" screws aha,i gotta start wearing my glasses again. :)

10-17-2004, 09:40 AM
Well, Dave, when you get a few more years on you, you'll learn to keep them glasses hangin' around your neck onna nerd-strap, doncha know. :)

10-17-2004, 11:06 AM
I keep reading glasses on the kitchen table, on the computer desk and in my truck. I would be admitting I need them if I hung them around my neck. :D

CX about wore you out about sticking to plywood, not much else to add there. :)

CX said something worth repeating though, use the flat side of the trowel to put only a skim coat of mud on the tiles, no need to build them up with extra mud.

Now, if we can get thru this thread without JB's french. :laugh2: