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Monday, July 13, 2020

What to expect with slimline porcelain and large format tiles

A global company with more than 80 years’ experience, Mapei is one of the most iconic adhesive and chemical manufacturers in the world, offering a wide array of products for DIY and professionals alike.

Now with large format tiles becoming the new standard for every day projects, due to ongoing research into new ceramic technologies, Mapei has been led to expand its range thanks to the research and development department, as well as its dedicated technical and training team. M

apei offers a wide range of products and services to meet every need of its end users, installation experts, builders, designers and architects.
With the aim of meeting the high demands of all the prestigious projects, as well as meeting Mapei’s high quality standards and expectations, in 2017 Mapei UK extended its product range by means of its new premium large-format adhesive, Mapei Ultralite.

The Mapei Ultralite range features single-component, high performance, and flexible, lightweight, cementitious adhesives with a long open time and up to 80% higher yield than traditional adhesives. Some of these adhesives also boast Mapei’s recognised Low Dust technology. The adhesives’ design makes each product easy to apply by trowel with excellent wetting properties, including very low emission of volatile organic compounds.

What is slimline porcelain?
Traditionally, standard tiles are made using wet clay, whereas porcelain tiles are formed from the dry dust of high quality porcelain clays. The result is a tile which is harder, smoother, and with a finer grain. While ceramics are baked to remove the high water content, porcelain tiles can be fired at a much higher temperature, producing a tile with a much lower water absorption rate. This makes them tougher, longer lasting and much more resistant to water and frost than ceramic equivalents.

The porcelain clays used are much denser, have a higher feldspar content, and contain fewer impurities than ordinary clay, giving porcelain tiles their greater strength and hard-wearing characteristics.

Typically a mere 4.8mm thick, slimline porcelain tiles are less than half the thickness of standard 10mm porcelain tiles. This results in a thin, lightweight tile with the same surface resistance as a traditional porcelain tile. Since the era of slimline porcelains, manufacturers have started gradually increasing the thickness again. However, with this additional thickness comes extra weight, as well as portability and design implications which may not meet site conditions.

There are two different types of slimline porcelain: one with no mesh backing, and another with a resin bonded fibreglass mesh. With the latter, the additional mesh backing reinforces the very thin tiles, making them more dimensionally stable. A slimline tile can weigh between approximately 7 to 14 kg per square metre, depending on the thickness. Smaller tiles can mostly be moved by hand but in the case of particularly large format tiles, for example 1,200 by 3,000mm, a minimum of two people is needed to manoeuvre the large tiles effectively.

To ensure tiles are not damaged during unpacking or installation, a lift frame can be used to support the tile.

Site handling and substrate preparation
Once the tiles have been removed from their packaging, care must be taken when putting them in position. Having a sufficient work space is extremely important to ensure that you have the necessary room to cut and install the tiles correctly. Particular attention should be paid when handling the tiles to avoid chipping or breaking the corners, and in some cases over flexing the tile can cause micro-fractures to appear which don’t show until the tiles are installed. To ensure the tiles are not damaged during unpacking or installation, a suitable lift frame can be used to support the tile from unnecessary bending or twisting.

Thin porcelain tiles may be fixed on conventional substrates normally used in the building industry, for example: concrete, cementitious and anhydrite screeds, proprietary screeds like Mapei Topcem or Mapei Mapecem, heated screeds, old ceramic floors, stone or metal, cementitious render or gypsum, and plasterboard and internal substrates waterproofed with cementitious products such as Mapei Mapelastic or synthetic resin products – Mapei Mapegum WPS and Mapei Mapelastic AquaDefense amongst others.

Prior to installation, the suitability of a substrate for this type of tile must be checked. The substrate must always be stable, well cured and strong enough to withstand the foreseen loads and changes in the room’s circumstances in the tile’s life time.

In a wide array of tiling applications, the one area which is often unfortunately discounted is the surface flatness and the room shape or dimensions. With tiles which can potentially reach a length of up to – and sometimes greater than – 3 metres, these concerns would need to be addressed before the installation.

Because of the reduced thickness of the tiles, the flatness of the substrate is particularly important. If there are voids or gaps in the substrate, or in the adhesive layer, the tiles may fracture if subjected to concentrated loads.

In accordance with British Standards BS5385, the flatness of the substrate must be checked with a straight-edge at least 2 metres long by placing it on the surface of the substrate in all directions. The maximum acceptable tolerance is ± 3 mm. If the high and low points exceed this value, the surface must be evened out using a suitable levelling product. Suitable products may include skimming mortars like Mapei Planitop 200, smoothing compounds such as Mapei Ultraplan Renovation Screed 3240 or patch repair products.

With underfloor heating systems being the new popular choice with their potential cost and space saving, additional precautions should be taken in the design and preparation stage. With heated screeds, follow the instructions normally applied when installing screeds and follow the guidelines given by the manufacturer of the heating system and screed. It is also important to commission the heating system after installing the screed, as prescribed by EN 1264 – 4 and BS 5385 – 3.

On the flip side of the coin, there are also electric-based underfloor heating systems which follow a similar commission principle, however the build-up is slightly different. As very thin tiles are being installed, and quickly referring to the substrate preparation above, a suitable smoothing compound would need to be used to encapsulate the heating element to remove all surface irregularities.

A lift frame can help support large format tiles during installation.

Preparation and installation
Some thin porcelain tiles currently being produced have a surface area larger than 3 m². This large size throws out the standard single person installation methodology, with two people being the minimum requirement for slimline porcelain tiles. That being said, to transport and cut tiles this size also requires special handling and cutting equipment.

When selecting a suitable tile adhesive for fixing thin porcelain tiles, care must be taken to ensure that they remain perfectly bonded over the years, and to guarantee the highest level of durability and quality under all conditions.

With the presence of meshed and non-meshed back tiles in the marketplace, so comes the need to adopt the adhesive selection. When there is a mesh backing the minimum recommended Mapei adhesive is Mapei Ultralite S2 which is produced in accordance with EN 12004. If no mesh backing is present, and the tile size is below 1,000 by 1,000mm, Mapei Ultralite S1 can be used (depending on the substrate).

The adhesive must be applied with a notched trowel using the back-combing technique, and the adhesive must be applied on both the back of the tile and on the substrate to guarantee that the tile receives 100% coverage. This application is essential to avoid leaving voids below the tile surface.

Setting out the tiles is also equally important; if there is inadequate spacing between each tile, there is the possibility of a tile failure through tiles cracking or tenting. As an example, when fixing tiles by butting them up against each other, the tiled finish is more or less comparable to a continuous slab and is as rigid as a single tile. If tiles are laid with a suitable spacing instead, the modulus of elasticity of the tiled surface is reduced, since the modulus of elasticity of the grout is much lower than that of porcelain. As a result, grouted joints help a surface to follow the different movements between the substrate and the tiled finish due to settling of the structure, hygrometric shrinkage, thermal expansion, etc., thus helping avoid stresses and potential detachment of the tiles.

There are other means to relieve stresses in the tile finish and the substrate, and they are called anti-fracture membranes. If used correctly, anti-fracture membranes such as Mapetex from Mapei can assist in dissipating the stresses created within certain larger format floor substrates. Substrates such as heated screeds and timber can put immense stress on the tile finish – more so with a slimline porcelain tile due to it reducing a number of grout joints. The requirement or suitability of an anti-fracture membrane should always be confirmed with the manufacturer.

The minimum grout widths vary by tile facial area of the tile. Examples include the following:

  • For tiles with a facial area <0.1 m2 with no side greater than 600 mm long, joints should be not less than 2mm wide
  • Tiles with a facial area 0.1 m2 to 1 m2 with no side greater 1,200 mm long, joints should be not less than 3mm wide
  • Joints between slimline porcelain panels should be increased pro-rata to panel size (e.g. for 3 metre long slimline porcelain panels the recommended minimum joint width between 3 m panels is 5mm).
  • Movement joints are just as important as grout joints, but apart from mirroring structural joints, and accommodating perimeter and intermediate movement joints, the rules for intermediate movement joints vary between project applications, therefore it is always recommended to refer to the designer and/or architect for guidance. British Standards BS5385 is also a good medium to help determine the best course of action.
  • As an example, the placement of intermediate movement joints can vary between heated and unheated subfloors.
  • The recommended bay sizes are:
  • Heated: The floor area should be divided up by intermediate movement joints into bays of size not greater than 40 m² with an edge length not greater than 8m
  • Unheated: The floor area should be divided up by intermediate movement joints into bays of size not greater than 100 m² with an edge length not greater than 10m

Grouts and sealants
Grout products are divided into two main categories according to EN 13888 depending on their chemical makeup; CG stands for cementitious grouts while RG stands for reactive grouts. Both grout options can be used with slimline porcelain tiles but the effectiveness would depend on the project location and expected future site conditions.

Joint sealants should be selected and applied in accordance with the guidance given in British Standards BS 6213. Generally, a sealant should be capable of accommodating the anticipated amount of movement without loss of adhesion to the sides of the joints, and be able to endure the normal service conditions affecting the installation such as resistance to water and ultraviolet light.

For more information on Mapei’s range of tiling adhesives, grouts, and construction chemicals, and how they can be used in your project, contact:
T: 0121 508 6970
E: info@mapei.co.uk
W: www.mapei.co.uk

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