tiling over an uneven stone hearth [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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06-29-2008, 04:34 PM
We are tiling our bathroom and have an area that is a little tricky. Around an old boarded up fireplace there is a remaining stone hearth that is raised 4mm above the floor boards. We want to tile over this making it indistinguishable from the surrounding tile.

We have layed plywood substitute board around - but not on - this area so now it is a few millimetres lower than the surrounding ply board. Can we simply use extra tile adhesive to 'build up' the tiles in this area making them level with the surrounding tiles?

Any advice appreciated.

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06-29-2008, 07:57 PM
Your stone hearth is now a little lower (few mm?)than the rest of the floor? If thats the case then you can make that up with some thinset. Trowel it on so it level with the rest of your floor, let it dry. I'd then use a membrane over the whole floor. Ditra would be good in this case because you wont be able to put mechanical fasteners into the stone hearth with the thinset skim coat (this prevents you from using most common backer boards).

A couple other things:

1. What exactly did you put on the rest of the floor? You called it plywood substitute board and I just want to make sure it is something you want under you tiles.

2. What/How is the rest of floor made? How big are the joists? How are they spaced? How thick is the subfloor? What tile or stone are you planning on putting down?

06-30-2008, 02:59 AM
Thanks for the response. A bit more info then.

The hearth actually started a few mm higher than the surrounding wooden floor. Now i have placed backer board on the rest of the area it is an average of a couple of mm below. Though unfortunately the level is not consistent so at the wall it was at the same height as the floorboards and is now around 5mm lower than the surface of the backer board. This means that if i put backerboard (or other) it will again be higher. My current plan is to build up the difference with thin set till roughly level. Let that dry and then tile again on top of that thinset with more thinset.

1) It's called no more ply which I believe is a fairly standard backerboard.

2) The rest of the floor is the original floorboards. I think the joists are about a 50cm apart. It's on the 2nd floor so no sub floor, just floorboards. The tiles are mainly standard white ceramic along with 10cm*10cm granite squares. That creates a slightly complicated staggered pattern. Furthermore the granite is 2 mm thicker than the ceramic. So I have a number of further questions about how to get the two level, and how best to cut the granite. But i thought one question was enough to start with.

Thanks in advance

06-30-2008, 07:24 AM
No More Ply is a backerboard product sold in the UK.

I think you would find it easier to build up your hearth with a portland cement based mortar. Use thinset, if the amount you need to fill is less than 1/4" (6 mm), or medium set mortar up to 1/2" (12 mm). Mason's mortar for over 1/2". Clean and vacuum the hearth to remove soot, dirt, and any loose bits of mortar. Dampen slightly, then dump in a batch of the mortar, press it down against the stone with a trowel, the screed (drag a straight board across the top of the backerboard) the mortar flush with the No More Ply. Let it cure. Treat the joint between the mortar and the backerboard as per the Mo More Ply instructions.

I got to tell you, this No More Ply products goes against most of the recommendations given for cement based backerboards used in the States. I hope your installation goes well.

06-30-2008, 07:39 AM
Welcome josephaedrus. How about giving a name? I take it from your notations in metric that you aren't stateside. We have folks from all over so tell us where you are located as well.

06-30-2008, 08:49 AM
bbcamp, thanks for the advice,

Given that the amount I need to fill is certainly less than 1/4" (6 mm), I am hoping to use thin set (I think the tile adhesive i have is classified as thin set). I have plenty of this already and it sounds like you are saying for this thinner difference it will be acceptable. I'll follow your instructions to level it and let it set.

It's a bit late now for me. But i'd be interested to know more of you concerns around No More Ply.

Thanks again,
from Leeds in West Yorkshire :)

06-30-2008, 09:57 AM
Joe, the instructions say to use an adhesive that you squirt on the back with a caulking gun, then you fasten the board to the floor with 8 screws. I would think that would lead to voids in the adhesive, which would be springier than if the board was embedded in thinset and screwed every 8 inches or so. Also, most of our cement-based backerboards require fiberglass tape and thinset at the joints. I couldn't see what the board was made of.

Does your tile adhesive come pre-mixed in a tub? If so, that's not what you need to fill your hearth. You want a portland cement based product that you must mix with water.

07-01-2008, 04:25 AM
I hear what you saying about the adhesive and it makes sense. The boards are already down and they feel reasonably stable to me so hopefully that will be OK.

I was suprised i didn't need tape and could still add fibreglass tape to the joints if you advise.

Also, i will be tiling against the skirting boards (I know this is less than ideal but they were old and proving difficult to replace.) Should i eith tape or fill the small gap between the board and the skirting before laying the tiles?

I think the boards are cement based.

The adhesive is not pre-mixed but is mixed with water. This evening i will check the brand name and add it here.

Thanks a lot for your advice, much appreciated.

07-01-2008, 06:03 AM
Do not tile against the skirting boards ("baseboards" over here). Leave about 1/8" to 1/4" gap, and caulk that joint. Hopefully, you left a gap between the backerboard and the skirting boards, too. It's all about expansion rates: Tile, backerboard and wood all expand and contract at different rates, so you need to allow room for this.