Tiling with Resin-Agglomerated and Mesh Backed Tiles

What is a Resin Agglomerated Stone?

Resin agglomerated tiles have become an increasingly popular choice of floor finishes over the last 20 years, as they offer a cost effective alternative to natural stone. These tiles are manufactured in an array of colours and are ‘engineered’ to have some improved mechanical and physical properties such as scratch resistance and flexural strength. Resin agglomerated tiles are sometimes called reconstituted or re-composed stone and in the US are known as Engineered Stone.

A resin agglomerate stone tile is a composite material, based upon the use of recycled natural stone aggregates or stone pieces which are then bound together at the manufacturing stage using a synthetic resin. The resin bound stone is then formed by vibration and compression under a vacuum to form large blocks. These blocks are then allowed to cure before being sawn into slabs, calibrated to the correct size and thickness, polished, then accurately cut into the required tile sizes.

The agglomerated stone to resin binder ratio has a direct affect upon the physical, mechanical and performance properties of the tiles. For example, use of quartz or granite agglomerates produce in general a harder wearing tile with increased resistance to acidic chemicals when compared with those based on marble agglomerates. Two main types of polymer resin binder are used in the tile manufacture and these are either epoxide or polyester.  Typically the ratio of resin binder to agglomerates varies from 5% to 7% (with 95% to 93% Agglomerate). The higher the percentage of resin present; then the greater the abrasion resistance is reduced. This is especially evident with increases in the Coefficient of Thermal Expansion of the tile.

Thermal Movement

The use of underfloor heating or undertile heating is increasingly popular as a heating choice within the UK. It can often provide cost effective, comfortable and unobtrusive heating. When considering a rigid tile finish, either directly onto a heat source or in areas where thermal gradients exist i.e. areas subjected to direct sunlight. It is important to understand how the heat change affects the different materials employed within the tiling assembly.

Materials may undergo dimensional changes when subjected to heat fluctuation. This is known as the Coefficient of Thermal Expansion. When considering the tile, the tile adhesive and the substrate, the Coefficient of Thermal Expansion for a typical constructional sub-floor such as concrete or cement; sand screed is similar to a cementitious based tile adhesive. However a resin agglomerated stone tile has a higher Coefficient of Thermal Expansion in comparison. In simple terms the tile has a high modulus of rupture, or measure of strength before rupture, and is being ‘restrained’ by the tile adhesive. However due to heating and cooling cycles, a relatively small amount of heat expansion and contraction can exert a high level of stress on the restraining layer i.e. the tile adhesive. The larger the tile dimensions, the greater the magnitude of the dimensional changes on resin agglomerated stone caused by the thermal expansion or temperature increases.

Moisture Movement

It is important to note that resin agglomerated stone tiles do have varying degrees of moisture sensitivity which means that these tiles can be susceptible to differential moisture expansion. This can often lead to a potential ‘curling’ of the tiles. The Tile Association (TTA) technical document on Tiling with Resin Agglomerated Tiles recommends that:

Cementitious floor screeds to receive resin agglomerated tiles should be completely cured and tested to ensure that they have a moisture content of not more than 2% by weight or 75% relative humidity using the appropriate test equipment and also that an appropriate adhesive is chosen” (Clause 3.5 Moisture Sensitivity).

Simply put, the use of a cementitious based tile adhesive or screed will introduce moisture directly beneath the resin agglomerated stone tile which may be taken up slowly by the tile. Some loss of moisture will occur whilst the tile joints remain unfilled; however this process will be slower. The tiles are available in various size formats including large formats (i.e. with one edge length 600mm or greater) up to typically 1200mm x 1200mm. The larger the tile in size, the more likely that moisture will become trapped at the tile/adhesive interface. In the case of some resin agglomerated tiles, this will increase the risk of curling of the tiles away from the tile adhesive bed. Therefore the correct selection of tile adhesive is essential.

For this reason, resin agglomerated tiles are not recommended for use infrequently wet areas e.g. areas of total immersion such as swimming pools or pool area walls and floors.

 Adhesive Selection

Resin agglomerated tiles are classed as neither ceramic nor strictly speaking a natural stone, being as previously discussed as a ‘manufactured’ or ‘engineered’ stone tile.

However, British standards code of practice BS 5385: Part 5: 2009 and floor tiling Design and installation of terrazzo, natural stone and agglomerated stone tile and slab flooring – Code of Practice offers the following recommendations in clause 11.2.1 of BS 5385::Part 3 2014: “To avoid moisture from the adhesive bed distorting resin-based agglomerated stone, reaction resin adhesives, or quick drying low alkalinity cement-based adhesives should be used”.

BAL manufacture suitable rapid drying, low alkalinity tile adhesives. Dependent upon the background substrate to which the tiles will be fixed, BAL POURABLE ONE mixed with BAL ADMIX AD1 may be used for floors or BAL RAPID FLEX ONE with BAL ADMIX AD1 for walls. Where the resin agglomerate stone is especially moisture sensitive use of a suitable reaction resin tile adhesive i.e. BAL EASYPOXY AG may be specified.

Adhesive Application

When installing a ceramic tile or natural stone tile using a tile adhesive, the accuracy of a sub-floor should be such that when placing a 2 metre straightedge on the floor that there is no gap greater than 3 mm. This is known in BS 5385 Part 3 2014 as SR1 (Surface Regularity).

If this is not the case, this may be rectified by the use of a suitable smoothing and levelling compound such as BAL LEVEL MAX, dependent upon the type of floor construction.

In the case of the installation of large format tiles, in particular resin agglomerated stone tiles, the surface regularity should be SR1 or better for both wall and floor substrates.

The tile adhesive should be applied using a suitable notched trowel to the wall or floor and in the case of large format tiles, additional back buttering of the tile with the tile adhesive may be required to ensure adequate adhesive coverage.

When fixing resin agglomerate tiles to both walls and floors solid bed fixing is essential to;

  1. Ensure, as far as is practicable, full contact is achieved between the tile adhesive and the wall or floor tiles,
  2. Eliminate voids beneath the tiles, which in floors are potential points of weakness under load and in wet areas, moisture may become trapped from the service conditions on site or during regular cleaning.

Environmental Consideration

As previously discussed, resin agglomerated tiles are not recommended for use in frequently wet areas e.g. areas of total immersion such as swimming pools or pool area walls and floors.

For domestic showers and wet rooms, generally it is important to seek further advice from the tile supplier or manufacturer with respect to their fitness for purposes in these applications. It is also important to establish what, if any, additional precautions may be necessary to take both during and following completion of the tiling installation. Fundamentally the wall and floor should be protected from moisture ingress/ leaks using a suitable waterproofing tanking system such as BAL TANK-IT.

Additional protection from potential water ingress may be afforded by the use of a suitable impervious reaction resin grout such as BAL EASYPOXY AG or BAL FLOOR EPOXY. However, as stated in BS 5385-Part 4: 2015: “The use of impervious grouts and adhesives is no substitute for a tanked installation” (clause 7.2.3 Installations not immersed but subject to occasional wetting, note 2).

It is also important to note that the fixing of resin agglomerate stone tiles is not recommended for external tiling using a tile adhesive. Where the tile is deemed to be suitable for use for external application by the supplier or manufacturer, for external facades they should always be installed using appropriate mechanical fixings.

The Importance of Movement Joints

The need for inclusion of movement control joints within any tiled installation is well documented in the BS 5385: Parts 1-5 suite of standards. Fundamentally movement from factors such as drying shrinkage movement, thermal and moisture movement (as discussed previously) will generate stresses within the tiling system which can lead to de-bonding or cracking of the grouting and/or tiles.

Where the resin agglomerate tile is deemed to be suitable for floors subjected to direct heat or heat from an environmental source, The Tile Association technical document Tiling with Resin Agglomerated Tiles recommends the frequency of movement joints needs to be increased. For example, BS 5385-3 advises that for floors subjected to significant thermal changes, tiles should be divided into bays of size not greater than 40m² with an edge length not greater than 8m. In order to allow for the anticipated increase in thermal expansion of the resin agglomerated tile installation, the bays of size of the movement not greater than 25m² with an edge length not greater than 6m.

Under normal dry internal conditions, the advice is that bay sized should be reduced to bay sizes not exceeding 36m² (100m² bays for ceramic tiles).

Mesh Reinforced Resin Backed Tiles

There has been an increase in recent years in the number of natural stone tiles i.e. marble or granite imported into the UK which has a mesh reinforced resin backing bonded to the lower interface of the stone.

Typically the resin polymers commonly used for this are epoxide, polyurethane or polyester of which polyester is the most commonly used. A fibre mesh is often embedded within the resin coating i.e. a fibreglass mesh.

The reasons for this vary from providing additional strength to the stone, particularly in the case of thin marble, limestone or granite, or sometimes it may be designed as a ‘temporary’ backing.

Unfortunately a polyester resin will have a much higher Coefficient of Thermal Expansion compared with the stone itself. Coupled with the surface of the resin which has a ‘waxy surface’ and may contain free styrene monomer, these will act as barriers to adhesion.

When fixing these mesh reinforced resin backed stone tiles, the bond strength achieved is totally dependent upon the quality and consistency of the resin/ mesh backing applied to the stone. This applies to both the dry and wet duty test conditions.

Factors which influence this are, for example;

  1. The tensile bond strength between the mesh reinforced resin backing and the stone, which can vary from strong to very weak.
  2. The chemical type of resin used e.g. polyester resin has a high coefficient of thermal expansion when compared with different types of stone and differing backgrounds/base.
  3. Variability in the quality and application of the mesh and resin between the same stone i.e. where mesh is not completely encapsulated in the resin or when the mesh is weakly bonded to the resin itself.

However the most fundamental factor when considering the feasibility of the use of a cementitious based tile adhesive conforming to the requirements of BS EN 12004: 2007 + A1: 2012 is that the tile adhesive is no longer bonding directly to the stone but to an intermediary (and potentially weaker) layer which has been introduced between the stone and the tile adhesive.

As an alternative to cementitious tile adhesives, reaction resin adhesives conforming to BS EN 12004: 2007 + A1 2012, could also be considered. However the use of a resin based i.e. an epoxide tile adhesive would prove to be very difficult, particularly where elevated temperatures may exist on site. In addition the amount of restraint offered to the mesh reinforced resin backed stone may counter-act against the anticipated levels of movement within any tiling installation, in particular where, for example any thermal and moisture movement is prevalent.

BS 8000: Part 11 Workmanship on building sites Part 11: Internal and external wall and floor tiling – Ceramic and agglomerated stone tiles, natural stone and terrazzo tiles and slabs, and mosaics – Code of Practice recommends that: “With large tiles and slabs any reinforcing mesh should be well adhered to the underside, and the mesh and adhesive should not obscure more than 25% of the underside of the tile or slab unless they are mechanically fixed”.

This advice mirrors that previous recognition is given for mesh backed mosaics which adhesives that the combination of mesh and glue holding the mesh in place should;

  1. Not cover more than 25% of the back of the tesserae
  2. Be no deterioration in the backing material and its glue whilst in service
  3. Be compatible with a cementitious tile adhesive in accordance with mosaic suppliers’ recommendations.

In conclusion, where a mesh reinforced resin backed stone is specified, unless the tile adhesive is able to bond directly to the stone to produce a contact area of 75% or more, it may be possible to consider removing the mesh reinforced resin backing altogether, but this must be undertaken following consultation with the stone supplier or manufacturer.

If this is not feasible to remove the backing without damaging the integrity of the stone, then consideration should be given to mechanically fixing. In the case of external wall cladding, BS 5385: Part 2 2015 advises that “Stone tiles which are resin mesh backed should not be used”.

 

 

A guide to sub floor preparation

Self-levelling floor compounds help level up small surface irregularities on new and existing bases and usually come in one-part or two-part forms. Easily mixed and simple to apply, they find their own level giving a smooth finish for laying tiles or other floor coverings.

Most levelling compounds can only be applied up to 30-40mm and will need to be used in more than one application or with other materials required. However there are some exceptions on the market such as BAL Level Max which can be applied from 2 mm up to 80 mm in one application.

It’s always important to remember that levelling compounds are never suitable as a finished, wearing surface, and that they should always be covered.

Typically; self-levelling compounds are suitable with most screeds, including sand:cement, anhydrite and flooring grade asphalt. However, when levelling timber floors, or screeds containing underfloor heating then only fibre-reinforced products are suitable i.e. BAL Level Max. Remember to check the products you’re using with the manufacturer to make sure they’re suitable.

Before laying a levelling compound it is essential to ensure that correct preparation of the sub floor is carried out.  Firstly ensure that the surface is clean, firm, dry and free from grease, dust and any other contamination which may be considered barriers to adhesion.

Any new concrete or screed must be left to fully cure according to the manufacturers’ instructions before applying any levelling compound. Ensure that any direct-to-earth sub-floors incorporate an effective damp proof membrane.

The majority of subfloors will also need priming. Floors such as concrete, cement:sand screeds, anhydrite screeds, cement:sand screeds with underfloor heated screeds and suitably constructed suspended timber floors.  Priming ensures that the levelling compound fully adheres to the substrate.  If levelling over timber boards where the joints are open, we would suggest using thin heavy duty tape to bridge the gaps.

When mixing your self-levelling compound always ensure you follow the manufacturer’s instructions. Typically, products like BAL Level Max are mixed by adding powder to clean water five parts powder to one part clean cold water by weight. We would always recommend mixing with an electric drill mixer at a slow speed i.e. under 300rpm.  Always mix until a lump-free mortar is achieved and allow the mixed leveller to stand for two minutes before re-mixing for 30 seconds.

Once the required consistency is achieved, pour the mix over the prepared substrate and spread to the required depth using a suitable steel finishing trowel or long handled blade. Work the mixture well into the corners, edges and around projections. When you’ve finished spreading the mixture on the floor, pour some more mixture onto the floor and spread that out and blend it in with the previous area.

Before allowing to cure, ensure that the surface is sufficiently smooth to receive floor coverings without any further treatment. If you are laying tiles or slabs, floors should be corrected to SR1 (Surface Regularity) – this is plus or minus 3mm or less over a two meter straight edge. We would not recommend the use of spiked rollers on a fibre-reinforced product (e.g. BAL Level Max) as this can pull fibres through to the surface. If any trowel marks do remain, rub down before the compound has hardened.

Always allow the new floor to set before laying your finished floor surface. Setting times can vary depending on your chosen product normally between 4 to 24 hours and is dependent upon your floor finish. For example, BAL Level Max can be tiled after 4 hours, but must be left to set for 24 hours for other finishes such as vinyl or carpet. This is to ensure that the covering is fully protected from any moisture in the screed which will diffuse through the screed and damage the surface if not left to fully cure.

In wet areas allow a minimum of 24 hours before waterproofing the levelled screed with a tanking system such as BAL Tank-it. Suitable for use internally or externally, BAL Tank-it is a rapid-dying cementitious waterproofing system. It can be tiled in 90 minutes and no priming or matting is required. Thanks to its EN Classification BS EN 14891, BAL Tank-it is suitable for a wide range of projects including total immersion such as swimming pools.

It can be easily applied with only a brush, roller or trowel and as well as providing outstanding performance, like BAL Level Max, BAL Tank-it comes with full back-up technical and on-site project support and a written 25 year guarantee for complete peace of mind.

One should always remember that self-levelling compounds, such as BAL Level Max, are not a substitute as a wearing surface.

Finally, we would always advise checking with the manufacturer or their technical advisors for before application to ensure project success.

At BAL our Technical Advisory Service is fully equipped to provide support to contractors, architects and tilers using levelling compounds – including NBS M40/M10/M20 specification assistance, on-site consultancy and expert technical advice.

Contact BAL Technical Advisory Service on 0845 600 1 222 or our Innovation and Technology Centre for training enquiries on 01782 591120.

Covering the whole of the UK, BAL Product Support Technicians offer practical knowledge and on-site consultancy and training to tiling and flooring contractors.

If you’ve experienced a problem on your installation whatever brand you’ve used, you can trust our PSTs to offer dependable solutions and remedies.  What’s more, we’ll even send samples away for independent analysis at our laboratories to find the cause of the problem.

 

By David Wilson, 

UK Head of Technical Standards and Information at BAL

Selecting the right tile adhesive

When selecting the right tile adhesive for your tiling project, a number of factors need to be taken into account including the substrate, type and size of tiles and the environment.

 

Selecting the wrong adhesive for the intended background/application could lead to unwanted consequences including the cracking or de-bonding of your tiles, causing you financial pain in repair and recompense.

Purely selecting an adhesive or grout on its BS classification is not always the be-all – as other factors may render your selection invalid.

Firstly, let’s look at the substrate or background.  Whether you’re tiling onto tile-backer boards, tongue & groove floorboards, sand: cement screeds or even existing tiles will make a massive difference as to what adhesive to consider.

For example, where floors need to resist some limited movement or vibration, then a flexible/deformable adhesive should be selected

Polymer modified adhesives/grouts have the addition of either powdered polymers, pre-blended in at the manufacturing stage or can be modified with a liquid polymer additive.  This enhances the physical and mechanical properties of the product.

One such example is BAL’s new Rapid-Flex One wall and floor tile adhesive. Fast, strong and flexible, BAL Rapid-Flex One is an all-round adhesive which provides a number of benefits to fixers including extended 30 minutes open time and 60 minutes working time (pot life) giving total control. What’s more, it is still ready to grout in just three hours – ensuring fast track project completion.

BAL Rapid-Flex One is enhanced with Fibre Strand Technology (FST) providing enhanced strength and a super smooth consistency for easier and faster spreading. With S1 classification – meaning it’s deformable – BAL Rapid-Flex One comes in just one white colour meaning it can be used for any tile type at the great value of a standard grey flexible adhesive.

Tile type and size also plays a significant factor in determining your adhesive and grout. Ask yourself “are my tiles porous?”, or are they glazed, fully vitrified, light-coloured/translucent or natural stone. Is the material you are using vulnerable to water-staining? Are you using large format or mosaic tiles and are they mesh-backed?

For example ready-mixed adhesives may be suitable for porous-bodied ceramic tiles, but for porcelain a highly polymer-modified cementitious adhesive would be recommended. Ready-mixed adhesives are also not suitable for floor tiling or for tiles over 300x300mm.

In case of light coloured or translucent natural stone, rapid-setting and drying white cementitious adhesives – such as BAL Rapid-Flex One – are recommended in order to minimise any potential risks of staining. A pourable adhesive – such as new BAL Pourable One – may also be suitable for floor tiling with large format tiling.

This is because they can be build up to large bed depths – up to 25mm in one application for Pourable One – when using uncalibrated stone or for patch repairs.

A new and improved alternative to BAL Stone & Tile PTB, it has all the same great benefits and is also available as just a white adhesive – meaning that only one bag is needed for any floor installation.

A highly flexible adhesive, it is particularly suited with underfloor or undertile heating as it resists thermal movement.

While BAL Rapid-Flex One and BAL Pourable One are suitable for most tiling installations, sometimes you need a little bit more flexibility and deformability when tiling to specialist substrates such as tongue & groove floorboards, single layer chip or plywood floor, floating timber floor, steel, epoxy coating and existing glazed tiles.

This is where you need a specialist tile adhesive such as BAL Single Part Fastflex. A one-part elastomeric adhesive, BAL Single Part Flexible is manufactured with rubber-crumb technology meaning it is highly deformable (S2) as well as sound-deadening, helping to achieve the requirement of Building Regulations Part E (Resistance to sound).

There are other factors which should be considered and more importantly are NOT covered by the tile classification. Some of these include ease of use, coverage, colour, pot life and adjustment time and cost.

 

 

A guide to tiling in wet areas

When tiling in wet areas such as bathrooms, showers, wetrooms, pools, etc. it is vital to make the correct product selection to avoid costly failures.

Ensuring your wetroom, bathroom or shower installation is fully waterproof is perhaps the most important part of any tiler’s work, because tiles, tile adhesive and tile grout on their own will not inherently protect against water damage.

Tank-it - CGI Pack Shot

BS 5385 Part 4 states that the use of a ceramic tile together with an impervious tile grout and tile adhesive are not a substitute for a tanked or waterproofed bath, shower or wet room installation. The effects of water damage are well known and documented.

Therefore incorporation of a suitable waterproof membrane is a prerequisite for a wet room installation, either within the building structures or ideally on the substrate surface prior to the application of ceramic of natural stone tiles.

Surface tanking membranes are ideal as they are able to prevent water from tracking through a screed for example into other areas.

In a wet room, waterproofing should be specified on both walls and floors.

A tanking slurry, such as BAL Tank-it, is a typical product that can be used to waterproof backgrounds prior to tiling.

A two-part product, BAL Tank-it has EN Classification BS EN 14891,meaning it is suitable for internal and external waterproofing including terraces, balconies and even fountains, as well as full immersion project such as swimming pools, hot tubs and spas.

Before tanking a background always ensure that it is flat, clean, dry, sound and free from contamination.

For example you may need to render walls, or on floors use a floor levelling compound such as BAL Level Max, to ensure SR1 surface regularity (3mm under 2m straight edge) as per BS 5385-5.

When checked with a 2m straightedge with 3mm feet at each end, any gap underneath the straightedge between points of contact should not exceed 3mm.

With some waterproofing / tanking products it may be necessary to prime the background first  (although this is not necessary with BAL Tank-it).

Make sure that all corners, junctions, penetrations and cracks in the substrate are adequately covered with scrim tape – this stops the tanking slurry from seeping into the background or substrate.

The tanking mixture can then be applied – usually with just a roller, brush, float or standard 4mm notched trowel.

Once applied, leave the tanking slurry to dry – this can be anything from 90 minutes with a product such as BAL Tank-it, to up to 24 hours with alternative products.

When selecting the right tile adhesive and tile grout for your wetroom, shower or bathroom, a number of factors need to be taken into account including the substrate, type and size of tiles and the environment.

For more information speak to your local BAL Product Support Technician or BAL Technical Advisory Service.

Keeping tilers and contractors fixed up with the latest techniques

As the first adhesive manufacturer to open a specialist training centre in 1992 for standards and fixing techniques, BAL understands that quality workmanship is paramount to an installation.

BAL Demo

Since it began to offer training courses to help tilers and flooring contractors maximise their skills, more than 100,000 people have received training from BAL with more than 16,000 people trained at a BAL training centre.

In fact since the company opened the doors to its new Innovation and Technology Centre (ITC) in Stoke-on-Trent in March 2015, nearly 2,000 people have been trained at the new site.

Complete with 40-seat auditorium (with standing viewing platforms), practical training bays, breakout areas and meeting rooms, the new facility leads the way in training and development in tiling and flooring.

Dave Rowley, Training Manager at BAL, said: “I believe that training is vital to the continued success of the company and the industry in general.

“Maintaining high standards and fixing techniques helps to prevent poor practices and incorrect specifications which can have a negative impact for all in the industry including manufacturers, distributors, specifiers, contractors and fixers.

“At BAL training is a key priority, which is why we have invested in our Innovation and Technology Centre to give everyone in the industry the opportunity to learn about the latest technologies and installation practices to enhance their skills.”

BAL provides a full range of training courses for apprentices, fixers, contractors, and distributors. BAL’s training is endorsed by The Tile Association (TTA) andthe Construction Industry Training Board (CITB) while the company has also been highly commended by the National Training Association (NTA).

BAL’s training courses aim to cater for a wide range of needs, from experienced  professionals looking to up-skill with new techniques, to inexperienced professionals or apprentices. Key courses include:

·         Introduction to screeds and subfloor preparation – a practical course on preparing, laying and rendering floor screeds.

·         Preparing and tiling timber floors – demonstrations and practical training on preparation/levelling, fixing and grouting to single layer timber, plywood and floating timber floors.

·         Preparing and tiling to anhydrite screeds – practical and theoretical training on preparing and tiling to anhydrite or calcium sulfate screeds, including the use of uncoupling systems.

·         Preparing and tiling to under tile heating – practical and theoretical demonstrations on preparing and tiling to undertile or under floor heating systems.

·         Tiling and grouting for hygiene or chemical environments – including the use of epoxy adhesives and grouts.

·         Preparing and tiling wetrooms – in-depth course on waterproofing/tanking wet rooms, fixing, grouting and essential products.

·         Introduction to adhesives and grouts – foundation level course on cementitious and ready-mixed adhesives and grouts, basic fixing techniques for inexperienced tilers/apprentices.

·         Five day wall and floor tiling course – introduction to preparation, setting-out, fixing and cutting of wall and floor tiles and including grout and finishings.

BAL also provides bespoke courses to suit individual training needs, for example, the company recently held a special one-day course for mosaic mural artists, and thanks to the flexibility of the ITC, more bespoke courses like this can be held at the centre.

A new course on the company External Tiling Solutions for balconies, ground-floor terraces and roof terraces has also been launched and is available to book through BAL Product Support Technicians (PSTs).

Launched this year, BAL’s External Tiling Solutions uses proven technology from sister company Gutjahr, which protects outdoor covering against the unpredictable British weather and diverse extremities such as rain, frost and heat.

Gutjahr System Technology from BAL offers designers and contractors innovative drainage, ventilating and uncoupling solutions for cantilevered balconies, roof terraces and ground terraces.

The one-day training course for tilers and contractors provides an overview of the system, practical demonstrations and theoretical presentations.

Those completing courses at BAL receive a certificate of completion, plus merchandise and product worth more that the course.

To find out more about BAL’s range of training courses and to book yourself a place visit www.bal-adhesives.com/training or call 01782 591100.

[FIRST PUBLISHED IN TOMORROW’S TILE AND STONE]

A technical guide to uncoupling systems

With today’s requirements for faster installation of tiling and the use of more demanding substrates, uncoupling matting and membrane are being used more frequently and in some cases a necessity.

Uncoupling principles have actually existed for centuries with the Romans being the first documented users of the building process which incorporated an “uncoupling” method.

These early practices used a mud bed to separate the substrate (a two-inch thick layer of packed and flattened sand and cement) and the tiles. Both systems use the separating later to provide an uncoupling buffer between the tile and the substrate, enabling the substrate to move independently to the tiles. Modern uncoupling system methods have dramatically improved, but the same basic principles still apply for today’s uncoupling mat systems which are now in common use on floor tiling installations onto a variety of different substrates.

Coming in many forms, from thin, lightweight matting such as BAL Rapid-Mat, traditional cavity mat systems like BAL Flexbone VAried, or truly uncoupled floating systems such as BAL Flexbone 2Easy for unprepared screeds, they give tilers and contractors piece of mind when floor tiling. Designed to provide a buffer layer when tiling onto floors, they protect against a variety of problems that can cause tiles to crack or de-bond.

One common problem is the potential for the substrate to contract or expand. In particular, newly-laid sand:cement screeds or concrete may contain large amount of moisture, which as evaporates, causes the screed to shrink. However, all substrates will expand and contract naturally due to humidity and/or temperature fluctuation and this is especially true where under floor or under-tile heating has been installed. What’s more, certain water-sensitive substrates, such as anhydrite screeds (or calcium sulfate) will lose their cohesive strength if they get wet. Wood is a hygroscopic material, and this, therefore, increases the potential risk of dimensional changes occurring within boards due to moisture expansion and drying shrinkage movement resulting in lateral movement stress being generated between the board background and the rigid ceramic tile finish.

Any movement, whether shrinkage or expansion, can cause stress cracks that can transfer through to the tiled surface, causing the tile to either fracture, or de-bond from the background. Uncoupling matting helps to prevent these lateral stresses from transferring through to the tiled layer by absorbing these stresses and transferring them evenly over the floor. Matting also has the ability to bridge static cracks i.e. shrinkage cracks up to 2 mm wide and joints between sheet & board backgrounds.

Another of benefit of modern matting systems is their suitability for waterproofing. In areas subject to moisture exposure where additional movement can occur, uncoupling mats can be used in conjunction with tanking products such as BAL Tank-it to ensure a combination of waterproofing and uncoupling can be achieved. When waterproofing or no priming of the matting is required, such as with BAL Flexbone VAried uncoupling mat, do ensure that the membrane and liquid coating can interface with the chosen drain. It is worth noting that anhydrite screeds and gypsum-based materials are not considered suitable for the installation of wet areas.

While the uncoupling membrane was originally devised for the installation of ceramic tiles, uncoupling systems are now recommended for use when tiling natural stone on all substrates. Importantly, uncoupling mattings are now recognised by most floor trade associations related to the tiling industry as a major benefit. Both the TTA and the Stone Federation of Great Britain recognise the value of using these products and also gives reference to their use in BS 5385 part 3, 4 and 5.

A great advantage of modern uncoupling matting systems, such as BAL Rapid-Mat, is their ease of storage and installation. Rapid-Mat, for example, is extremely lightweight and weighs just 8.5kg per 30m roll.

Its printed gridlines make cutting and trimming around up-stands extremely easy with only a pair of scissors or a utility knife. Once the mat has been cut to size and the floor has been correctly prepared, free from dirt and debris, a bed of suitable flexible tile adhesive should be trowelled on using a 4mm x 4mm notched trowel. Flexible adhesives should always be recommending when tiling onto substrates at risk of lateral movement. The trimmed matting should then be laid onto the freshly applied adhesive bed ensuring that it is applied within the open time of the BAL adhesive selected.

BAL Flexbone

If you want a traditional cavity mat system, why not choose a product such as BAL Flexbone VAried.

Unique to BAL Flexbone is the patented GripLock Technology and unique bone structure.

The patented design has been independently tested to provide the highest shear strength (providing more accommodation of higher levels of lateral movement) and the highest tensile strength (to stops tiles ‘popping-off’, or cracking under pressure). These highly flexible and deformable properties ensure all tile installations are protected from lateral movement and pressures, while a special fleece provides for vapour pressure compensation.

As well as providing long-term benefits in terms of strength and flexibility, the unique bone structure also makes for significantly faster installations as the design ensures the trowelling-out of adhesive on the surface layer is fast and easy.

Fixer trials have shown that the unique bone-shaped cavities are much easier and faster to fill with adhesive than the conventional square or round cavities.

Less adhesive is required, and trials indicate areas can be completed circa. 30% faster.

Perhaps more unique to the UK market is BAL Flexbone 2Easy – a floating cavity mat system – this means that no adhesive is required underneath the mat i.e. the mat is truly uncoupled!

Because no adhesive is required, as long as the floors are level and solid, preparation of the substrate is reduced to a quick sweep of the floor. No removal or residue, no removal of laitance and no priming of the surface is needed. This means that contaminated and stained floors, wooden floors, cracked screeds and mixed substrates can be tiled immediately.

As well as time savings from the lack of preparation, materials costs are also significantly reduced with no need for primers, plus a massive adhesive saving of 2kg/m², when compared to laying bonded cavity mat systems.

Time trials indicate the removal of subfloor preparation for installations provides a circa 50% time saving!

Lengthy waiting times on new screeds are avoided as Flexbone 2Easy can be laid on new sand:cement screeds when they are ready to be walked on, or new anhydrite screeds that aren’t fully cured (up to 1.5% CM residual moisture). This means no more projects on hold for weeks on end waiting for the screed to dry!

Fast-track installation is possible as any residual moisture in the substrate is distributed evenly through a system of perforations and channels in the mat, meaning the screed can fully cure under the tiling with no issues.

Because BAL Flexbone 2Easy is laid loose as a floating system, it is perfect for heritage projects where it is necessary to protect historic, sensitive substrates, or rental properties where tenants cannot alter the original décor, plus areas where the ability to change the floor fairly regularly can be a requirement – e.g. retail stores.

Once the matting has been applied, the tiling can begin immediately. Again when tiling onto an uncoupling mat system we would always recommend the use of a flexible tile adhesive that is highly polymer modified e.g. minimum C2 cementitious adhesive.  For large format tile and natural stone, it is recommended to use a pourable thick bed adhesive such as BAL Pourable One, applied with a suitable large format trowel. Pourable thick bed adhesives such as BAL Pourable One will cure and not shrink even when applied at a higher thickness than typically recommended by the industry, ensuring that all voids beneath the natural stone are filled and proper adhesion is secured.

BAL Rapid-Mat, compared to the traditional cavity mat systems, uses less adhesive (approximately 20%) on the matting.

Non-cavity uncoupling mat systems are perfect for use in commercial or domestic environments, with some products actually capable accepting loads on floors following installation due to a condensed profile with almost no compression. This makes them perfect for car showrooms, hospitals, and shopping centres, areas where vehicular traffic is present, and areas with mosaics tiles.

What is certain is that uncoupling systems will continue to grow in popularity and will need to be considered at every stage of the design and build process, particularly with the growth of tiling in areas where it was previously deemed unsuitable.

by David Wilson, UK Technical Services Manager, BAL

First published in Contract Flooring Journal.

Tiling onto Calcium Sulfate (anhydrite) screeds

Calcium Sulfate or anhydrite screeds have grown in popularity over the last decade as they offer substantial benefits over traditional sand:cement screeds.

Easy to lay, low cost, fast-drying, pumpable, self-levelling and offering minimal shrinkage, anhydrite screeds are perfect for domestic or commercial projects. They are also suitable for underfloor heating so long as the pipes and associated heating elements are covered with at least 25mm of screed.

However, despite the numerous benefits associated with anhydrite screeds, fixers and installers need to aware of potential problems.

These types of screeds contain anhydrous (dry) Calcium Sulfate and aggregates instead of a cement-based binder. The binder comes as either an alpha hemi-hydrate (a stronger and harder crystalline form) or anhydrous Calcium Sulfate. When water is added the binders will form calcium Sulfate dihydrate – more commonly known as Gypsum. This reaction stops when the vast majority of the Calcium Sulfate binder is used up and is generally complete after a period of 3-7 days, leaving the remaining water to evaporate through the surface of the screed.

Before laying onto Calcium Sulfate screeds it is vital to ensure that the moisture content is at the correct level for the required floor finish. Typical values for moisture sensitive floor finishes are less than 0.5%  Water by Weight  or less than 75% relative humidity for impermeable floors and less than 1% w/w for more permeable floors.

As a general rule thumb the drying time for a Calcium Sulfate screed, so the moisture content reaches 0.5% w/w, is approximately 1mm per day up to 40mm in ideal drying conditions – i.e. air temperature of 20C with a relative humidity not greater than 65%. Drying times will significantly increase for thicker screeds or those in poor drying conditions.

Accelerated drying of Calcium Sulfate screeds may be used once the screed is at least 7 days old. It is at this point that we would recommend commissioning any underfloor heating. The system should be increased by approximately 5°C per day until the maximum required working temperature is reached or as per the underfloor heating manufacturer’s recommendations. This should be maintained for a minimum of one week, before being gradually reduced to around 15-20°C. Do not exceed a temperature of 55°C. Use of dehumidifiers will also help.

Before laying tiles or other finishes onto Calcium Sulfate screed one of the most important tasks is the removal of laitance.

Laitance is a weak layer of fine particles deposited on the surface of the screed as the anhydrite cures. This layer is too weak to tile onto and can also inhibit  drying  of the screed. Many of the failures we see are as a result of contamination of the adhesive by laitance – highlighting the importance of carrying out this step.

Laitance should be removed by light abrasion using a suitable sanding machine i.e. a rotary floor scarifier and a 60’s grit sandpaper. Remove excess dust completely with a vacuum cleaner. Abrading the surface is best carried out 4-6 days after the application of the screed and can assist in the drying out process. Scarifying the surface is even recommended with low laitance Calcium Sulfate/anhydrite screeds as this further aids adhesion.

All traffic should be kept off the screed until it has hardened sufficiently in accordance with the screed manufacturer’s instructions and should always be protected from contamination and damage from other trades. It is best to protect the screed fully until the flooring is applied using boarding.

If not protected as the project progresses it may result in the wearing or grinding down of the screed’s surface. If this does occur then further surface treatment may be required. Moisture should also be avoided as any reintroduction of water can result in damage to the screed integrity and may affect any installed heating pipes.

Before tiling we would recommend applying a primer to the prepared screed surface before application of the tile adhesive. Priming created an effective barrier and assists in making the surface more stable.

When selecting your tile adhesive, consideration should be given to factors such as the tile type, and the type and method of cleaning the floor whilst in service – i.e. how wet the finished floor may become and what are the risks associated with limited water penetration. Slow or rapid-setting tile adhesives can be used, depending on the tile type and environment.

When the adhesive is cured, the joints between the tiles should be filled with a suitable grout – please note that a minimum of 3mm for floor tiling is recommended.

For ceramic tiling movement joints will be required in these installations. Any movement joint, or joints likely to be subject to movement, in the Calcium Sulfate screed should coincide with the movement joints in the tile bed. Movement joints should be incorporated as outlined in British Standard BS 5385-3, 2014 Clauses 6.8 and 7.1.6. For heated screeds also refer to The TTA technical document Tiling to Calcium Sulfate based screeds

Last, but not least, before tiling onto Calcium Sulfate screeds we would always recommend getting professional technical advice from manufacturers to ensure your installations look great and last the test of time.

By David Wilson, UK Technical Services Manager

(First published in Contract Flooring Journal)