Travertine tiles on plastered wall - weight issues.

[Tim Watts]

Hi,

Just started the shower room tiling (floor first).

I'm using 200x100x10mm travertine for everything. One thing has occurred to me though - these are quite heavy. My scales are busted, but comparing to a glass of water and tile in each hand, I'd estimate each tile to be around 0.3kg or slightly more - rather heavier than a similar sized ceramic tile.

That comes around 20kg/m2 and I've just read that skimmed plaster is only rated to 20kg/m2.

This is not something I'd considered...

I am wondering, once the floor is grouted and sealed, whether to line the walls with screwed tile backer board (the heavy stuff) or whether I'm worrying too much?

Most of the walls are new celcon block with virgin plaster.

One wall is not - and has been skimmed 3 times in its life over the plaster/sand undercoat on brick.

Cheers,

Tim

PS - the tiling is contracted out - too much for me to do and I don;t really do natural stone. But I've been involved in the prep.

Tiler is not overly concerned, but OTOH it would be a messy and expensive failure and we're not too late to switch some backer board in (he can't do the walls for a month)

[Tim Lamb]

In message , Tim Watts writes

Bit sideways... how are you intending to seal them?

I have been searching for ceramic *travertine effect* tiles in foot square dimensions for weeks. Plenty in America/Canada but rare here in the Orange pattern I am after.

Fall back is real stone but I am nervous about sealing in the wet room and utility areas.

[newshound]

That's in tension, presumably? So you would be on the limit if you were tiling the ceiling.

But on the walls, at least once they are grouted they are rather like a very thin wall. Gravity is holding them in place.

I'm pretty sure there won't be any issue, especially if you are having them done by a professional, who should be well used to recognising dodgy plaster.

[Capitol]

I've never had tiles fall off a plastered wall except when the glue failed. IME plaster only fails when the bond to the backing layer is poor and never as a result of loading. OK I can remember one episode where a PE injected insulating foam blew the plaster off the wall during installation but that was once in 50 years.

[Tim Watts]

Yeah - that's the bit that concerns me...

Last night I found 2 loose areas of plaster and had to chop them off.

And 2 weeks prior I had to fix a patch were some joker had plastered over a patch of old wall paper.

I've just had a look at Hardibacker 12mm. There's plenty of space so loosing an inch overall is not really a problem.

About £250 worth of board (we would not bother with fiddly bits like window rebates, these are small areas) and something like 9 screws per

1200x900 board.

And a 100kg/m2 load. It is looking like a smart idea...

[Capitol]

Please tell med if you find the ceramic version. I've been looking sand coloured tiles for nearly a year, but the UK is obsessed with 57 varieties of beige or grey!

[Capitol]

There's a 6mm version available.

[Tim Watts]

No, in shear. That surprised me. I had never heard of that before. But I've seen it repeated several times.

I was actually looking at SBR priming skim plaster as I'd had that fail over a 1m2 area - just peeled off. Seemed to be a funny area where the plaster was so highly polished the diluted SBR did not penetrate. I wire brushed it and re did.

That's when I found 3sq-ft of failed plaster - some failed at the final skim, most failed 3 skims ago (original, you can see the layers).

It all rather points to some rather dodgy plaster and I think I should consider this a timely warning!

Not here - it will be UFH, so there'll be a silicone seal between walls and floor, so the walls are not supported off the floor.

OTOH, in the last 10 minutes, I've just worked out that I;d need about £250 of 12mm Hardibacker with 9 screws per board. It claims to be score and snap and I'd not bother with small fiddly bits like window rebates - so it does seem like a wise move.

[Tim Watts]

Tile sealer...

I'm less bothered as it's all masonry - in the worse case, my screed gets damp and the worst that can really do is rot the ali foil on the celotex it sits on. Any slight damp in the walls can breathout the back.

I got the tiler to add tanking membrane corner strip just on the wall-floor joint as this will be siliconed and the most prone to future leaks. I'm reasonably confident about grouted tiles on the ground floor holding out and the UFH should keep them dry.

[Tim Watts]

I wondered that, but the website says that's for floors.

12mm is OK - no one would notice the loss. No sanitryware is fitted yet

- so no real constraints :)

It's typical in this place - often get a curve ball from some historic bit of dodginess.

[Huge]

[18 lines snipped]

Good news; I have them on the floor in our en-suite. Bad news; I have no idea who made them. I can look at the back of the spare ones, if you'd like?

We have real travertine behind the sink and a highlight strip through the shower. We sealed them with Lithofin - one coat before grouting and two afterwards. The bloke in the shop said it should be good for a decade or so.

[Tjoepstil]

the weight of the tiles is taken by the grout.

All the wall has to do is stop a very thin tile wall from buckling...

Euler's slender column theory will give you chapter and verse

[Tim Watts]

I kinda see that - but what if the wall to floor joint is sealed with silicone rather than grout?

[Tjoepstil]

well seal it first with silicone, then tile over, then grout over the silicone. looks better :)

seriously, its all shear force anyway. plaster takes a LOT in shear

[Tim Watts]

I was worried about the expansion of the screed with UFH - but did a calc based on the coefficient of expansion of concrete (14e-6/K) and 10C to 40C over 3m length is about 0.15mm

I could silicone between tiles and wall before wall tiles go up - if the lowest grout joint hairline cracks it will not matter.

OK - but I'm seeing this 20kg/m2 figure a lot:

and I'm pretty sure I will be exceed that but maybe 20-30%

[Tjoepstil]

If its any help Ive done extensive tiling with marble slate and other stones on plain pb no problems

[Tim Watts]

This isn't PB (which the same docs say is good to 32kg/m2.

This is a masonry wall with 1 undercoat dating to the 1950s and 3 skims.

See why I'm worried :)

[John Rumm]

I think you are worrying too much...

when you think about it, once grouted, a fully tiled wall is mostly self supporting - the top tile rests on the one below etc. All the adhesion to the wall is doing is stopping the stack of them falling over. What load there is on the wall is all in shear.

Note also that the load is fully distributed, and also introduces its own additional strength to the wall.

[Tim Watts]

Just nipped down the Post Office and weighed a tile: 480g for 10x20cm.

So that's about 29kg/m2 including 4-5kg for adhesive.

Next question:

Marmox or Hardibacker?

I've used the former a lot on floors - I like it.

I did not realise, but:

says the boards can also carry 100kg/m2 and they are lighter to work with and would add some insulation value (at least render the wall warmer to the touch.

Marmox seems to be a good option here...

[Tim Lamb]

Size is the first problem for me. My wife wants the floor tiles in the utility area laid diamond pattern. This only really works for square tiles. The other issue is that manufacturing and fashion seem to have engaged in a race to impress with the largest possible tile.

The result... a dearth of 305x305.

I have a few beige ones left over from the last shower room here and have managed to match those.

PM for a *findings list*.