Speed bump [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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04-23-2004, 01:06 PM
Hey Guys,

I have compelted building a shower seat as John instructs. It came out good (Here is a pic) I was very patient to keep everything flat and plumb knowing that my poreclin tiles are not pliable.

With that in mind, I have what I consider to be a problem and would like your opinions before I proceed. When hanging the CBU (Hardibacker), I have two sheets (one joint) which is not flush. I have already taped and jointed all the seams. What is the maximum this can be off? Is there any tolerance which can be taken out by how much thinset is used to lay in the tile. I am currently 3/16" off at this one seam. Do I have to grind it back and than feather it over with some thinset before tiling?

Thanks for all your help.


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Mud Hog
04-23-2004, 01:36 PM
Hey Bud,
Looks Great! As far as the tolarance, what material are you using on the walls? The reason I ask, when you work with stone you usually have enough mud on the back of the tile to play with the wall.


04-23-2004, 01:47 PM

I am using 12 x 12" porcelin tiles. It will be a diaganol pattern.


04-23-2004, 01:59 PM

Just a clarifying question. When you say 3/16" off on this one seam, I'm assuming that along this seam one piece of Hardibacker is higher (or extends outward) beyond the other creating lippage of 3/16"? Conversely, this is not a case where there is just a 3/16" gap in the joint between the two sheets?

If the two seams are blocked with studs or other wood material from behind, any idea what is causing this lippage in the first place?

04-23-2004, 02:33 PM

No gap, just the "lippage".

I am not sure. I suspect either one of the studs is bowed, or maybe one of the pieces of HardiBacker is bowed.

Either way, still have the 3/16" lippage.


Steven Hauser
04-23-2004, 02:50 PM
Hi there,

Yeah, it stinks when you work so hard to get the substrate flat to encounter this, that said, I agree that you can feather this difference out when you apply the tile.

Or you can smooth some thinset along the plane leading up to the lippage to float it out before tiling.

Either way you can work with it.

My .02

04-23-2004, 02:52 PM
Gotcha. Like you I would think 3/16" is quite a bit, even using a 1/4" X 3/8" trowel. Personally I don't like a 1/4" X 3/8" trowel on 12" porcelain which tends to on the thin side. I get too much thinset squeeze out in the grout joint with 3/8". And with that speed bump I know you would have problems with a 1/4" X 1/4" trowel.

Hang tight. Someone will come along with a good fix.

P.S. After re-reading the Thread, I think Steven has you covered. He must have snuck in there while I was trying to figure out how to spell 'Gotcha" :D

04-23-2004, 04:01 PM
Thanks for the advice. I will do a little grinding and feathering before I tile. I am almost at the end and I would hate to not have it as perfect as possible, because you know everytime you take a shower you would be looking at the "speed bump".


04-23-2004, 04:50 PM
Have you been back-buttering all the tiles? If so that might have raised the rest of the field up enought to give you a little more cushion/wiggleroom on the one right over the hump.