Liquid tanking and how it affects weight limits.. - Tile Advice

[Time's Ran Out]

Above is a job I went too a month ago. The contractor said we’ve tanked the walls for you! I told him I wouldn’t tile the slope as it was and with 900x300mm tiles. Why he asked!
I used my thumbnail to pick a bit off then proceeded to peel it like an orange - that’s why!
So my question.
If the substrate is primed correctly ( not like above) and liquid tanking applied, what is the weight limits for tiles.
I read Isomats reply to an earlier thread that informs it reduces the weight tolerances so what does it make an old plaster finish wall take - >23kg/m or what?
Thanks for any input.
John

 

[Old Mod]

Depends on the system used John.
From memory, Ardex WPC and Bal’s tank it one, or whatever it’s called, does not effect weight limits.
The other Bal tanking system reduces the limits

 

[Old Mod]

What about a membrane John?

 

[Flintstone]

I’ve always been under the impression that the brush on systems don’t effect the weight limits if applied correctly. I have been recently using Tilemasters new one coat tanking kit, which does not require any priming before applying it according to them. They are usually good at explaining the limits and dos and do nots on there products and they dont mention any weight reductions.

 

[Time's Ran Out]

That’s it Andy - no mention of weight limits.
Marc - behind this thread is I went this morning to an old stately home where one of the servants rooms (off the gym and boot room) was in the process of becoming a wet room - but not by me!!
I noticed the 600x300 Topps Tiles in the store and yes they were for the wet room. Weight of tiles is 23.7kg/mt on box + adhesive. When I saw the prepared room for tiling by others, the same happened - a thumb nail removed tanking and old paint. The customer will overboard with wedi and mechanical fix but it seems there’s no specification for weights.
They must have spent £100 on liquid tanking and he now believes it’s going to be belts and braces, instead of it being a waste of £100.

 

[Flintstone]

Tanking even tho he knew it was going to get over boarded ?

 

[WetSaw]

Is that just down to poor prep?

 

[Time's Ran Out]

Tanking even tho he knew it was going to get over boarded ?

No the tanking was going to be tiled direct.
He asked what I’d do and I suggested over boarding with Wedi + adhesive + mechanical fixings.
I wouldn’t tile onto painted walls and I don’t tile onto tanking with anything too big ( full bodied porcelain over 27kg/m )
Fortunately the customer didn’t think it was sour grapes on my behalf as I wasn’t doing this room ( and the wine cellar was along the hallway I’am providing a geometric floor for) and he took it as good information.

 

[John Benton]

Good question TJ, never had any problems (as far as I'm aware) using paint on liquid tanking. Funny you should mention it though I always try to scratch the edge of the tanking to see if it peels, but not really given it any thought as it never has.

I guess if say, for example a skimmed wall has a very polished surface then chances are it will not bond, same as emulsion paint. I've seen it before where the plasterer has got the finish like glass and the painters play hell with them, you can literally just rub with your finger and the paint peels.

 

[Old Mod]

Is that just down to poor prep?

All tanking will peel if it’s laid down too thick Paul.
It does stipulate in the instructions, the thickness of each coat. They must be built up with thin layers or its the same as an over thick coat of primer. All it does is form a skin which can be peeled straight off.
That not withstanding tho, tanking will quite often peel if it’s actually peeled, if you get my meaning. A bit like taking backing off a self adhesive strip.
However, just cos it peels from a corner, doesn’t necessarily mean it’ll separate from the wall.
The forces applied to the tanking when the wall is tiled is not the same as peeling, so it can be perfectly ok. The tile is trying to pull at an area, not peel from a corner.

 

[John Benton]

Bit like the size of a camels foot on the sand, it’s the distribution of the weight, rather than picking one specific area

 

[Old Mod]

Bit like the size of a camels foot on the sand, it’s the distribution of the weight, rather than picking one specific area

 

[Qwerty]

I asked this very question when I attended an @Mapei UK Marketing ceramic tiling course a number of years ago. Mapei aquadefense was around then, so it was only Mapegum they had for domestic tanking. They said consider it the same as weight limits on skimmed plaster.

 

[John Benton]

So what they are saying it has no effect on the limit if you're tanking skimmed plaster, but it would lessen the weight allowance on Hardie per se

 

[Qwerty]

Thats how it was basically explained John, yes