Crack isotlation membrane

[tfs]

Do any of you guys incorporate a crack isolation membrane when tiling over concrete slabs? If so do you always do this as standard?

I just ask out of curiosity as this is not something I ever hear anyone discuss.

How big a problem is telegraphiong with ply floors. I havent been tiling for years so havent realy come across any damged of failed jobs that I have done.

I havent tried to counteract against this in plyfloors but Im thinking that maybe I should as I always fill joints between ply if Im installing karndean floor.

Does applying adhesive over ply joints prevent telegraphing?
Any comments on the subject would be appreciated.

[garythetiler]

i would always recommend either a backer board or uncoupling membrane when tiling over a wooden substrate , telegraphing, not heard of that term before but assume you mean the joints of the ply boards breaking either the tile or joint in the tile istallation this will happen if there isnt the correct expansion joints in place or if there is any bounce in the floor hope this helps you,

[tfs]

apparelntly there is always the risk of telegraphing even when securing very well to the floor etc and I have read that this can happen with backerboards too. I would assume that this is why we tape joints of the backerboard. (as a preventitive approach)

Does anyone trowel any compound over ply prior to fixing tiles?

I reckon that the coupling membrane you mentioned would be best bet in these cases. I would not imagine that the majority of guys would use this on most domestic jobs though (extra, cost, work etc)

Would you agree its something most people just take a risk with? or perhaps not fully aware of the possibilty of problems that could arrise?

Fair enough we are advised that to tile over ply is fine if its secured well to the floor, but there is always going to be some expansion/ movement etc and this is true with concrete slabbs to, which could always crack with warmth, cold etc.

I have also heard that when tiling over wooden floors some guys preffer to lay a sheet of membrane and then staple some wire mesh to the floor and lay a thin bed of cement or adhesive over this and tile as normal once this has dried. (simlar idea to the new nicobond mesh I guess) ,again some extra work and cost if you have already taken the time to ply. I would be happy to do extra work if costs were met and profit still made.

I havent seen the cost of liquid forms of isolation membranes but I would think that this would be the easiest and quickest option.

Any knowledge any of you guys have on the matter please share./

[lucius]

I have heard an argument that it is not a good idea to mesh because it has different thermal properties and movement can cause problems this also applies to render how true this is i dont know but ime sure the expanded metal companies would dispute this .
Lucius.

[garythetiler]

tfs there is no guaranteed method for fixing on to a wooden substrate all you can do is follow whats refered to as best practice , i have seen failure arise with uncoupling membranes but i am yet to see a failure with backer board that doesnt mean one is better than the other ,it is only my opinion based on what i have encountered , if you follow british standard 5385 proceedures you will be reducing the risk of failure, the mesh method you refer to, was a method popular over 15 years ago ,the mesh was normally stapled directly to the wood and then the mesh was backed off with adhesive with additive, ardion 90 or bal bond . and then tiled, if you fit sand and cement screeds over a wooden substrate which is popular in the usa then a chlorinated polythene sheet is laid and wire mesh is laid through the screed
crack isolation membranes and uncoupling systems were developed to deal with a particular issue of freeze and thaw, they then developed into the uncoupling systems we have today, in certain circumstances they are essential and in others they are not needed Dave has posted an extremely informative article called Understanding the tiling shift read this and it will may help you with your question

[Dave]

Cheers gary..

I think this section from Ditra should Help tfs with this..

Overcoming Problems Of Tiling On Timber

Any timbered substrate for tiling is always problematic -- floors more so than walls. What makes it difficult to tile effectively is that timber is particularly susceptible to movement caused by moisture. Most failures, where Schlüter-Systems are called in as troubleshooters to solve the problem, are where tiles have been bonded directly to the timber substrate. While certain tile adhesives will allow you to tile directly to timber, they don't always provide a total protection against the effects of movement.
Many failures occur at the joints, where the timber boards are abutted together, because there is differential movement between the two. We've been on site on many occasions where we can tell from the tiled surface exactly where the board joints are, because the tiles have cracked above every joint.
To guarantee the integrity of such installations, the first thing is to verify that the timber substrate is capable of taking the weight. If it needs to be strengthened, add extra noggins or support, or overply the substrate. Then, the best way to prevent the transfer of stresses to the tiled surface, is to lay an uncoupling membrane.
It neutralises joints and differential movement in the timber substrate, ensuring stresses are not transferred to the tiled surface.
An example of how it solved a major problem on a timber substrate involved a large old house that was being renovated into flats. The existing timber floor was simply planked floorboards, about an inch thick and eight inches wide, just butted together.
But in various places there were gaps between the boards of up to eight millimetres wide -- and the floor was about an inch out of level. To plug the wider gaps between the boards, a proprietary filler was used, a fibre-reinforced self-levelling compound was then poured over the complete timber floor area; once that had hardened the next day Schlüter-DITRA was applied, and then the tiles were laid on top.
As long as the substrate is capable of taking the weight of the tiled surface, Schlüter-DITRA can be applied directly to any existing timber -- including plywood and chipboard.

And even in older properties with butted planks, small gaps of around two millimetres between the joints can be successfully bridged with membranes such as Schlüter-DITRA without the need for fillers.
The builders also wanted to install walk-in showers on the first floor -- and the membrane provided waterproofing protection, too.
To fix Schlüter-DITRA, use a bonding adhesive that's appropriate for the individual timber substrate, and apply using a 3mm x 3mm, or 4mm x 4mm notched trowel. The anchoring fleece on the underside must be fully engaged in the adhesive to provide a mechanical bond to the substrate.
Then set the tiles directly on top so the tile adhesive is mechanically anchored in the cut-back cavities of Schlüter-DITRA.
Schlüter-DITRA is usually specifier-led in large commercial applications, but is just as important in protecting tiles in the home, even though some installers don't include membranes in domestic jobs because they're worried it'll push the price up too much. However, because their use will extend the life of the installation, and guarantee it against bulging, cracking and debonding, many installers are now including Schlüter-DITRA in their price, and fully explain to their customers why it should be used.

[tfs]

cheers for the info guys