Understanding The Tiling Shift

[DHTiling]

Understanding The Tiling Shift.. Uncoupling Membranes - Uncoupling Theory Part 1 - Schlüter-Systems

Today's installation systems allow the incorporation of ceramic and stone tile on virtually any surface. In addition to traditional projects such as bathrooms and kitchens, other tile applications which are becoming increasingly popular include worktops, exterior balconies, and even bedrooms. However, the development of these contemporary systems highlights a shift in common knowledge about the physical dynamics of the floor assembly regarding the relationship between the covering and the substrate.
Thousands of years ago, European builders developed a successful means of installing tiles which virtually eliminated the transfer of stresses within the various layers of the overall assembly, thereby eliminating failures.
These builders understood that a forgiving shear interface between the building structure and the tiled surface was necessary in order to allow the two elements to move independently.
The installation method used by these European builders was a "sandwich" comprising a structural base and a layer of sand.
Then a mortar bed - a mixture of sand, cement or other binder, and water - was laid, with the tile adhered on top. The critical component in this sandwich was the layer of sand, which uncoupled the tile covering from the structure, allowing the two to move independently. The layer of sand supported the tile covering under heavy loads, while, at the same time providing a shear interface that effectively prevented movement from the structural base being transmitted into the tiled surface.
The use of this "sand strata" method is virtually extinct today, largely due to the introduction of thin-set mortar in the 1960s, which allowed the tile to be bonded directly to the building structure - i.e. to concrete or plywood, etc.
It can be argued that the most monumental change the tiling industry has undergone in the last millennium was a shift away from uncoupling the surface covering from the building structure, to a technique where the tile was bonded directly to the substrate.
It's based on the theory that the principle element needed in a direct-bond system to achieve a problem-free tile installation, is an extremely strong bond between the tile and the substrate, and the mortar bed was eventually perceived as unnecessary. It quickly became popular because the ease of installation allowed anyone - not just trained installers - to fix tiles.
However, this created a problem in many cases, with tiles eventually cracking, splitting or becoming debonded from the substrate.
Bonding the tiles directly to the building structure creates what is known as a "force-transfer assembly," because the physical dynamics of each layer in a tile assembly are vastly different from each other. The substrate, whether it be timber, concrete, or gypsum, etc., expands and contracts due to changes in temperature and moisture levels. The tiled surface also expands and contracts, but at a different rate.
As the surface is directly -- and firmly -- bonded to the substrate, naturally-occurring stress cracks, and movement in the substrate, both manifest themselves in the tiles as cracks, splits, tenting, or debonding.
Correctly applied modern technology can achieve the same results for the thin-bed method, as the protection devised by those European builders thousands of years ago for their tiling methods.

 

[DHTiling]

Uncoupling Membranes - Uncoupling Theory Part 2 - Schlüter-Systems

Bringing History Up To Date - Understanding The Tiling Shift

Tiles debond from the substrate because bonding the tiles directly to the building structure means there is no "give" between the two separate parts of the assembly, and movement and stress cracks in the substrate are transferred to the surface, damaging the tiles. While the methods of installing ceramic tiles and stone have changed over the years, the physical dynamics of the assembly have not. The old traditional methods, used for centuries, addressed these dynamics by uncoupling the tile from the structural base through the use of a forgiving shear interface, in the form of a layer of sand.
Following the development of the thin-bed method of bonding the tile directly to the substrate with a very strong adhesive, problems occur because the rigid tiled surface moves at a different rate from the substrate.

An installed tile surface can be compared to a large sheet of glass. In addition to being a hard, brittle material, the tile also expands and contracts in reaction to environmental changes, but at a different rate from the substrate.
So, when the tile is strongly bonded directly to the substrate, it results in what is known as a "force transfer assembly," where this differential in the movement manifests itself as cracks in the tiled surface. One of the major causes of tiling installations failing is where stresses from the substrate are transferred in this way, into the finished covering of stone or ceramic tiles.
The solution is to install an uncoupling system - which utilises modern technology to bring the "sandwich" technique bang up to date. (This sandwich, used by ancient builders, comprised a structural base and a layer of sand, then a mortar bed - a mixture of sand, cement or other binder, and water - was laid, with the tile adhered on top).
Neutralising stresses by uncoupling the building structure from the tile is particularly important with the use of today's thinner, larger-format tiles and lightweight building materials.
The up-to-date method of uncoupling uses the Schlüter-DITRA polyethylene membrane, which safeguards installations over any even and load-bearing substrate.
Tiles will move independently from the screed because of different thermal expansion and contraction. Schlüter-DITRA neutralises this differential movement, preventing stresses being transferred to the tile covering. The system supports applied loads by transferring them directly to the load bearing substrate.
Schlüter-DITRA is a polyethylene matting with a fleece laminated to a grid-type structure of square cavities on the top. The fleece is adhered to the substrate with standard adhesive, and the adhesive used to stick the tiles actually anchors into the dovetailed configuration, mechanically locking the tiles onto the top. The cavities allow any stresses that occur between the substrate and the tiles to be neutralised evenly in all directions.
The matting itself has four main functions -- uncoupling, waterproofing, vapour diffusion over green screeds, and it bridges cracks such as timber board joints and cracks in screeds.
It protects the surface covering over a wide variety of substrates, including green concrete; green cement-based screeds, gypsum-based screeds, poured bituminous screeds, plywood and pressed wood, existing tile coverings, solid vinyl coverings or coatings, mixed substrates, gypsum plaster and plaster block, mixed masonry, and metal.
Today's tile installers have an array of materials and installation systems at their disposal to meet the UK's growing demand for this ideal surface covering. Setting materials are available in ever-increasing numbers to address the variety of substrates and tiles commonly used. Underlayments continue to be developed to protect tiles and guarantee a successful installation. Other developments include drainage, waterproofing and uncoupling membranes for use in both interior and exterior applications.
It's crucial that today's installers understand the physical dynamics of the entire tile assembly in order to achieve consistently successful results. Accepted wisdom regarding tile installation is now shifting away from the direct-bond philosophy, back to an understanding of the need for a forgiving shear interface to absorb stress.
This shift, with its resulting successful installations, represents a great deal of potential for the professional tiler.

 

[DHTiling]

Uncoupling Membranes - Early Tiling Teaser - Schlüter-Systems

Not dealing correctly with problematic substrates is one of the major causes behind the failure of many tiling installations, where stresses from the substrate find their way into the finished covering of stone or ceramic tiles.
For example, Schlüter had been called in to advise a tiler who had been asked to lay ceramic tiles in the kitchen of an old house which was being renovated and extended. The existing screed had several cracks in it, and the tiler was worried that in time, the tiles will debond and crack, which is exactly what would happen if the tiles are laid directly on to the screed. Because of different thermal expansion and contraction the screed will move at a different rate from the tile, and without the right solution will lead to disaster. Even if the tile adhesive has a flexible polymer in it, thermal movement in the screed -- particularly at the joint of the cracks -- will be too great for the adhesive to hold the tiles down. However, an uncoupling system -- also referred to as a separation system - will allow the tiles to move independently from the substrate.

Schlüter-DITRA has been developed specifically for uncoupling the building structure from the tiles. It's a pressure-stable polyethylene membrane with a grid structure of square cavities and an anchoring fleece laminated to its underside. The fleece backing becomes anchored in the tile adhesive on the substrate. On top of the membrane the adhesive is anchored into the square, cut-back cavities, and the tiles are installed on top. The membrane neutralises the cracks in the screed, and can absorb up to around 2-3 mm of horizontal movement. We were also able to advise the tiler on fixing onto the floor of a new conservatory at the house. BS recommendations are that you shouldn't tile on a new, green, screed, for at least 28 days, but the owners wanted him to do it before that. He was worried that if he did, the installation was likely to fail in the future.

The recommendation of 28 days is to allow for movement and shrinkage to take place in the green screed. But using Schlüter-DITRA actually means you can get on to the screed much earlier. Depending on the weather and time of year it could be as little as a couple of days. Basically, you're looking at being able to apply the membrane as soon as the screed can support weight. If you can walk on the screed and your shoe doesn't leave an impression in it, you can install the membrane and tile immediately afterwards. The membrane actually slows down the drying process of the screed, minimising shrinkage and eliminating most of the cracking which could occur. Also -- especially over floating type screeds where you've got insulation -- it'll minimise the curling effect of the screed, so all in all, using Schlüter-DITRA on a green screed not only protects the tiles, but gives you a better screed as well. And if you can get off site earlier, because you don't need to wait 28 days before tiling, you can get paid earlier too!

 

[DHTiling]

Tiling On Anhydrite Screeds - Schlüter-Systems

While anhydrite screeds are growing in popularity throughout the UK, they are not without their critics, especially as a number of flooring installations over anhydrite screeds have failed. There are also many installations, of course, which have been completely successful. Like with fixing any flooring surface onto any type of substrate, long-lasting integrity can only be ensured by proper and adequate preparation.
While the Contract Flooring Association has published a technical paper on the generic installation of floor coverings onto these calcium sulfate-based screeds, Schlüter-Systems Ltd., is increasingly being asked about the specific requirements for a successful ceramic or stone installation on an anhydrite screed.

As with all screeds, as long as appropriate steps are taken, there is no reason why tiled surfaces over anhydrite screeds cannot stay looking good for many years.
However, the choice of a ceramic or natural stone floor on anhydrite screeds needs careful consideration at the design stage - and contractors should consider bringing in tiling contractors who are familiar with fixing to calcium sulfate screeds, or, at the very least, seek advice from the tile manufacturers or suppliers - as, indeed, they should for all types of substrate.
One of the key considerations for a sound tiling installation on anhydrite screeds, is the preparation before tiling. The Tile Association recommends that where a calcium sulfate screed has been used - particularly where the finished floor may be exposed to moisture - a watertight membrane is installed.
According to the applicable standards, the residual moisture of such gypsum-based screeds should not exceed 0.5% prior to the tiles being installed. However, The Tile Association points out that with the use of a special separating - or uncoupling - system, tiling can commence on an anhydrite screed with a residual moisture content of 2% (by volume). It states: "One speciality separating system is a pressure stable polyethylene membrane, manufactured in a configuration that allows the tile adhesive to mechanically bond into the surface of the system. The separating function allows any stresses, such as drying shrinkage, that occur between the substrate and tiled surface, to be accommodated.
"Interconnected air channels on the underside of the separating system remain open allowing moisture from the substrate to evaporate, thus neutralising the vapour pressure in the calcium sulfate screed."
If required, the screed surface may need to be pretreated (sanding or priming) in accordance with industry standards and manufacturers' recommendations. A typical polyethylene membrane, as recommended by The Tile Association, is Schlüter-DITRA, which can be applied using a suitable adhesive that is suitable for the substrate.
It protects the screed against moisture penetration from the surface; especially important, as gypsum-based screeds are particularly sensitive to moisture and must be protected from additional moisture penetration.
Anhydrite screeds are a mixture of screeding sand and binder. If tilers are unsure of whether the screed they're to work on is, or isn't, anhydrite, they should always ask. Information about the screed should be kept in the building owner's Operation and Maintenance Manual.
MOVEMENT JOINTS
Provision should be made at the design stage for the thermal expansion of the screed and surface covering. Industry guidelines for ceramic and stone coverings require movement joints to be placed at all perimeters, and where tiling meets restraining surfaces such as steps, kerbs, columns and fixed plant etc.
Intermediate movement joints should be placed in accordance with the covering requirements, which, for ceramic tile and natural stone flooring is between 8-10 metres in each direction. Ideally the tile fields should be kept as square as possible.
Where underfloor heating is installed within the screed layer, movement joints should be used to divide the tile fields into areas of no more than 40 square metres, with the longest side no more than eight metres.
The movement joint should pass through the covering, adhesive bed and screed.
Movement joints should be placed in the screed in line with industry guidelines, however, because of the difficulty of forming such joints in the required precise location while the screed is being laid, it is advisable to form intermediate joints in non-heated screeds by using a dry cut floor saw to cut through the screed when the tiling is being installed.
The structural movement joints in the bed and tiling should be sited immediately over, and be continuous with, the joints in the base.
This is just a brief overview of what is needed for a successful ceramic or stone installation on an anhydrite screed. For contractors who are in any doubt whatsoever about any aspect of tiling onto these calcium sulfate-based screeds - Schlüter-Systems Ltd ([email protected]), who are members of both The Tile Association and the Contract Flooring Association - will be happy to advise on the suitability.

 

[DHTiling]

http://www.schluter.co.uk/2808.aspx

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.

 

[grumpygrouter]

Great posts there Dave. Should give a good insight to how ditra works for those that don't know.

 

[DHTiling]

It's not just a thread for Ditra russ.......we need tile fixers etc to understand why problems happen and how best to overcome them......A lot of failures are lack of knowledege......

 

[grumpygrouter]

Maybe I would have been better putting "membrane" instead of ditra but you get my drift...

 

[DHTiling]

Another add on to this...

Movement Joints

Ceramic and stone tiles can be subjected to a variety of strains and stresses caused by movement in the tiled surface. Movement joints compensate for the movement of tiles which extends down through the tiles, the bed and screed layer below. They create a tile field which moves independently from those around it, and should be included at set distances in floor and wall tiles, in accordance with recommendations from the British Standards Institution (BSI). Technology governs the amount of movement that can be absorbed - and therefore the degree of protection given by the joint - through the size of the profile and the compressible material used. Pre-formed surface joints will usually accommodate movement up to 20% of the movement zone width. A 10 mm joint will extend and compress by approximately 2 mm. One of Schlüter's stress-relieving movement joints, the Schlüter-DILEX-KS, has a movement zone of 11 mm, which will accommodate up to 2.5 mm of tile movement.
Because there are specific movement joints for specific types of application, most tiling failures are caused by using joints that aren't suitable for what is being demanded of them. The correct technology in terms of width and material - brass, aluminium, stainless steel or PVC - must be taken into account when specifying movement joints.
Transition Profiles: Edge Protection For Tiles Meeting Other Flooring Surfaces
All too often, where ceramic or stone floor tiles join neighbouring surfaces such as timber, carpet, vinyl or laminate, the edges of the tiles can crack and chip, and even debond from the substrate. An appropriate profile will prevent these problems occurring. The technology behind Schlüter-SCHIENE, such as its specific angle and wall thickness, means it transmits point loads into the substrate and surface covering, protecting the edge of the tile from damage.
For adjoining surfaces of different heights, Schlüter-RENO-U, Schlüter-RENO-TK and Schlüter-RENO-RAMP have a fixed sloping arm to provide stepless transitions - thanks to the shallow angle of Schlüter-RENO-RAMP and its long-sloped transition edge, it is easy to use with wheeled traffic and creates stepless transitions to comply with disability requirements. Schlüter-RENO-V has an adjustable sloping arm to accommodate different heights. The anchoring legs for these profiles is fixed underneath the tiles.
However, there is also a profile that can be retro-fitted to adjoin different types of floor coverings at the same height -- Schlüter-RENO-T overlaps both surfaces, preventing the edges from being damaged when subjected to mechanical stress.
Stair Nosing Profiles

The Schlüter-TREP range of slip resistant stair nosing profiles forms a clean, decorative stair edge that is highly visible, while protecting it from damage. Some have a replaceable plastic tread insert. For those fixed at the same time as the tiles, the anchoring legs are installed beneath the tread tiles, with the surface tread improving safety and protection. Specific products are available to comply with current DDA requirements.
Wall Corners And Edge Profiles

The outside edges of tiled corners - indeed any exposed edge of a tiled surface - can often look unattractive and become damaged. This is because many tiles on the market today don't have a glazed, finished edge.
Specially engineered profiles are ideal for providing the dual function of combining an attractive finish, with protecting the vulnerable outer edge of the corner. Profiles are available in a wide variety of materials (including stainless steel, aluminium and chrome plated brass), colours, surface finishes and designs to co-ordinate with the tiles and grout. The technology of the Schlüter-QUADEC, Schlüter-RONDEC, Schlüter-JOLLY and Schlüter-ECK-E ranges focuses on the anchoring leg fixed behind the tiles, and the protective, finishing, edge.
Some also come with matching inside and outside corner pieces for elegant connections.
Balcony and Terrace Constructions

A wealth of technology has gone into developing protection and drainage systems for balconies and terraces, incorporating waterproofing and uncoupling membranes, a passive capillary drainage system, and movement joints (as described above) as well as systems developed specifically for such exterior applications.
For example, Schlüter-TROBA is a separation and drainage layer for use above a horizontal waterproofing layer, and below a screed or gravel. It consists of a pressure stable polyethylene sheet with perforated studs for reliable drainage.
The technology behind the Schlüter-TROBA-STELZ range was developed specifically to aid in the installation of large format pavers. They are polyethylene rings placed where the slabs meet, then filled with fresh mortar. The corners of the pavers are placed over the rings and tapped to the correct height and alignment.
Waterproofing assemblies on balconies and terraces often lack sufficient height to connect smoothly to door connections and other fixed building elements. This led to the development of Schlüter-TROBA-LINE, which is a stainless steel channel that guarantees drainage, even with low connection heights.
To complete balcony installations, Schlüter created its Schlüter-BARA and Schlüter-BARIN ranges of finishing profiles and gutter systems. Each has its own appropriate technology, including providing a functional frontage with a drip lip, protecting the exposed edges of the screed bed and the exposed edges of the floor assemblies. The Schlüter-BARIN gutter system is connected to the balcony edging profiles, and elongated slots at the back make it possible to slope the gutter up to 30 mm.
The technology behind each individual product combines to provide a full protective, drainage and finishing system for balconies and terraces. The technology also allows for a number of variations to take preferences of style and functional requirements into consideration.