Classification of materials during the facing works

Modern construction market offers a wide range of products designed for facing works. They include professional materials for flooring, damp proofing, tiling, grouting, etc. Sometimes it’s really hard to determine which product to choose and which properties to look for. Please find below some details on their standard classification.  

Classification of materials in view of technological order during the facing works:
• Preparation of the substrate,
• Installation (if necessary) of the under-tile damp proofing,
• Tiling,
• Curing the facing surface.

Substrate preparation
The appropriate preparation of the substrate prior to the commencement of the facing works is crucial and needs to be done in a correct way. Before the installation of the first tile we should:

• Check the plane continuity. Find and reveal any gaps, cracks or scratches.
• Check the evenness of the substrate plane.
• Check the location and the way of execution of the peripheral and intermediate expansion joints. Clean away the mortar residues and the aggregate.
• Check the moisture content.
• Check the hardness and the resistance of the substrate.
• In case of significant unevenness, one should remould and polish the substrate.
• Apply the additional layer in case of unevenness or necessity of elevating the substrate level. The additional layer may be made of plasters, screeds based on cement or gypsum (anhydrite). 
• Deconstruct and then reconstruct the substrate including necessary thermal insulation and damp proofing.
• Prime the substrate. Priming reduces the absorption of the substrate so water is not absorbed from the mortar, moreover it equalizes and unifies the absorption. It prevents from stress appearance and in result from loosening off the substrate. It also strengthens the substrate superficially and within its layer.

Under-tile damp proofing

The under-tile damp proofing course is a layer which separates the substrate surface from the moisture. Water absorption and capillary rising may deteriorate the physical and chemical properties and in consequence lead to destruction of such materials as cement screeds and plasters, aerated concrete blocks, and, in particular, wooden and gypsum substrates which are very vulnerable to moisture.

Damp proofing can be divided depending on the application area into:
• internal,
• external.

Depending on the amount of components into:
• single component, ready-to-use, in the form of mass or water dispersion,
• two-component or more, to be mixed together in a determined ratio; in the form of mass after mixing; generally they consist of:
– dry component A = cement, aggregates, fibres, dry additives,
– liquid component B = synthetic resin.

Due to the function they fulfill when protecting the substrate:
• damp proofing,
• waterproofing.

Depending on the applied thickness:
• lightweight –  prevents against damp,
• medium weight – prevents against not-pressurized water,
• heavy weight – prevents against water under pressure.

Single component insulations are designed mainly for indoor use, at damp and wet areas, in laundries, bathrooms e.g. showers (inside the shower cubicles), around bathtubs and sinks, etc., as damp proofing course. They are based on water dispersion and are able to obturate minor scratches. They are resistant to high temperatures and chlorinated water. However, they are not resistant to hydrostatic water pressure, thus they are not suitable for insulating the pools. Their water vapour permeability is low, therefore they are not recommended for insulating the terraces. Application temperature is between + 5°C and + 30°C. The consistency provides easy application with a brush or a trowel. Apply at least in two coats; do not exceed the thickness of 5 mm. The substrate beneath the insulation should have the absorption equalized – this means that it should be primed if necessary. Do not apply onto damp substrate, otherwise the insulation will not get the desired adhesion and may loosen. Insulation dries for several hours. Generally tiling can be performed after 24 hours from the application.

Two-component insulations for lightweight damp proofing, medium weight waterproofing against not-pressurized water e.g. on terraces or heavy weight waterproofing against water under pressure, e.g. in swimming pools, water reservoirs, on foundation walls and in basements at areas of high ground water level. After drying they form a layer similar in texture to rough rubber.

Due to the fact that such insulations are vapour permeable, they are particularly recommended for waterproofing terraces above any residential rooms. They are flexible and capable of obturating scratches of up to 1 mm wide. They are applied in minimum two coats of thickness not larger than 2-3 mm – the first coat is rubbed into the moistened surface with a brush, and then distributed with a use of a notched trowel and finally smoothed. Some manufacturers recommend embedding the acrylic mesh into the coat. The mesh is used here only in view of simplifing the application with appropriate thickness.

Application temperature is between + 5°C to + 30°C. After application, the coat should be protected from direct sunlight and precipitation. Depending on the manufacturer, the finishing layer may be applied just after 24 hours, or 3-7 days. Generally insulation is resistant to UV radiation, so sometime it may be not covered with a finishing top coat, providing the caution on the foot traffic on it.

The damp proofing system additionally consists of: sealing tapes, internal and external corners, pipe sleeves for installation passages and outlets (grilles). They ensure tightness at critical places such as corners and installation passages in the sealed surface. They are made of synthetic rubber coated with fibres and with the perimeter of synthetic mesh. The fibres provide good adhesion to the damp proofing material applied beneath them. Damp proofing works should start with application of the sealing tapes and corners.

Adhesive mortars

In order to fix the tiles to a wall or a floor properly, one should use special mortars for tiling. The adhesive for tiles is simply formed by a mixture of aggregate, binder and water. The binder in cement mortars is represented by high quality cement or fast-setting aluminous cement, however a resin may also work as a binder. In reactive and dispersive adhesives the role of the binder is played by epoxy resin with a hardener or by polymer dispersions respectively. The aggregate is formed by selected sands, quartz and limestone powder. Adhesives contain also various additives which enhance the technical and operating parameters of a mortar.

To systematize the adhesives classification in the European Union, the harmonized standards were introduced. According to the EN 12004 standard, we can classify adhesive mortars and compare their performance. Adhesives are divided into types and are labeled according to the binder they consist:

• C – cement; adhesive mortars based on cement; to be mixed with water,
• D – dispersion; single component adhesives in form of ready-to-use masses. Due to high vulnerability to moisture these adhesives can be used indoors in dry rooms only,
• R – reactive; two-component adhesives, e.g. polyurethane and epoxy, that are prepared with the use of chemical reactions: the first component – a hardener, initiates the binding and crystallization process in the second component.

Each type of adhesive, depending on its technical characteristics is also divided into two basic classes and is labeled with:
• 1 – standard setting adhesives; adhesion > 0.5 N/mm² after 28 days from the application; they are referred to as basic adhesives,
• 2 – adhesives of improved parameters; adhesion > 1.0 N/mm² after 28 days from the application; they are referred to as adhesives of increased adhesion.
 
Each class is divided into subclasses or optional classes and is labeled with:
• F – fast setting adhesives; adhesion > 0.5 N/mm² after 6 hours from the application, 
• T – adhesives with reduced slip; slip < 0.5 mm,
• E – adhesives with extended open time (t > 30 minutes); after setting (28 days) the adhesion is higher than 0.5 N/mm².

To systematize and clearly define the concept of flexibility, so eagerly used in regard to the adhesives names, the standard has been amended with the deformability concept. It characterizes mortar ability of plastic deformation and maintenance of the material consistence in given load conditions. In order to determine the deformability parameters of the adhesive, one should form the samples of mortar as described in the standard and perform a loading test. The adhesives may be given the following deformability classes according to the test results:

• S1 – the deflection is within 2.5 and 5 mm,
• S2 – the deflection is above 5 mm.

Types, classes and subclasses may be combined in sets which uniquely identify the adhesives parameters. The labeling 
C2 TE S1 according to the standard stands for the adhesive mortar with a cement binder, improved parameters, reduced slip and extended open time, deformable in the range of 2.5 to 5 mm.

Other parameters of the adhesive mortars:

Let us explain some basic terms which define the adhesives parameters. Manufacturers are obligated to place this information in the technical data sheets and on the packaging. The parameters depend on the ambient temperature, humidity and the substrate type. Low temperature and high humidity may result in extending the default time periods determined in the parameters. On the other hand, high temperature and low humidity tend to shorten the default time periods. The parameters are determined for the temperature in the range of 21-25°C, relative humidity between 45 and 55% and the air flow velocity in the working space of less than 0.2 m/s.

Open time – it has already been mentioned in case of the adhesives classification. It indicates the amount of time which the freshly applied adhesive can be left before it is covered with tiles. This is the time when the adhesive maintains its adhesion properties; the end of the open time is indicated by the appearance of the thin coating on the adhesive surface.

To verify whether the open time is not over yet and the tiles can be still fixed to the applied adhesive, we can perform a so-called “thumb test”. In order to perform it, one should apply touch the mortar. If the adhesive sticks to the skin and marks it, this indicates that the tiles can still be fixed. On the other hand, if the adhesive does not mark the skin it means that the open time is already over and the tiling cannot be continued. Then, the adhesive should be removed from the substrate and discarded. Do not mix it with the fresh adhesive from the bucket, because it will shorten the open time.

The open time for adhesives is at least 20 minutes. The open time for adhesives labeled with letter E (E stands for extended open time) is at least 30 minutes. One should keep in mind that open time parameter depends on the aforementioned temperature and humidity.

Pot life – it is determined by the manufacturer. This is the time when the adhesive is good to use. Its beginning is set when the components are mixed together (in case of two-component reactive adhesives) or when the adhesive is mixed with water (in case of cement mortars). Pot life determines the beginning of the adhesive bonding. When the pot life time is over the adhesive is no more suitable for use. It should be discarded – adding water will not fix the problem. Under any circumstances one can add water to the bonded mixture of adhesive and water.

Adjustment time – within this time one can still adjust the position of tiles laid on the adhesive layer. Naturally the adjustment time depends also on the temperature and humidity.

Floor access time – after this time one can enter the room where floor was recently tiled and load the tiles with the weight of a single person. This is important information which determines how much time must pass before we can walk on the fixed tiles.

Full load time – after this time the cladding laid on the adhesive can be fully loaded. Full load time indicates also that the adhesive is fully set.

Criteria for the adhesives selection

A vast selection of adhesive mortars can cause big trouble for unexperienced contractors. Most of all, one should consider the following factors when selecting the appropriate mortar:

In regard to the substrate:
• construction material,
• workmanship: evenness, stability, strength,
• absorption, resistance to water and moisture,
• possibility of shrinkage and expansion, substrate operation,
• covering with layers of under-tile waterproofing,

In regard to the place of application:
• outdoors,
• indoors,
• dry area and with negligible moisture load,
• damp area,
• wet area.

In regard to the purpose of compartments and surfaces, and thus loads:
• residential housing,
• public access buildings,
• industrial facilities.

In regard to the dimensions of tiling elements and their quality:
• mosaic,
• small format tiles e.g. 5×5 cm up to 30×30 cm,
• medium format tiles e.g. 40×40 cm up to 60×60 cm,
• large format tiles e.g. 60×90 cm, 120×90 cm and more,
• boards e.g. 120×200 cm,
• thickness of tiling elements – therefore their weight,
• maintenance of surface evenness: convexity, concavity.

In regard to the cladding type:
• wall ceramics,
• stoneware,
• milled rock,
• natural stone.

When choosing the adhesive one should check whether it complies with the requirements concerning the substrate, application, water resistance, deformability, strength, and what is particularly important for the customer – profitability, in other words, value for money. As we wrote at the beginning: a vast selection can cause big troubles. How to choose or rather how to match the appropriate adhesive in view of the surface and cladding? This information is included in the section about the work technology.

Consumption of the mortar is, on average, approximately 1.5 kg/mm/m² and depends on the substrate evenness and the size and evenness of the tiles. In addition, it depends on the method of the adhesive application and size of the trowel notches used for the mortar application. For example, if we apply the adhesive with a trowel with notches of 6x6mm, assuming that while spreading we reduce the adhesive coat by approx. 2 mm, the obtained adhesive layer is approx. 4 mm thick. This means that consumption equals: 4 mm x 1.5 kg = 6.0 kg/m². Thanks to the careful works planning based on the knowledge of the substrate and the tile quality, we can calculate the amount of adhesive needed for the particular work.

If there is a need to cover the tile with a layer of an adhesive using the flat side of a trowel, then one should add approx. 1 mm to the adhesion layer, which in total results in consumption of 1.5 kg per 1m². Moreover, if we need to apply the adhesive on the tile with the use of the notched side of a trowel, with a view to better filling the space beneath the tile or because of the significant substrate unevenness, then the required adhesive amount should by multiplied by two.

Grouts

Grouts for tiles are classified according to the EN 13888:2009 standard “Grout for tiles – Requirements, evaluation of conformity, classification and designation.” This standard amends the previous one from 2004. It introduces several changes. The most important of them is the reduction of certain technical requirements for cement grouts: bending strength must be currently at least of 2.5 N/mm²(according to the standard of 2004 it was at least of 3.5 N/mm²) and the contraction must not exceed 3 mm/m now (previously the requirement was up to 2 mm/m).

In addition to technical changes, the standard also introduces a change of symbol of increased resistance to abrasion. Currently we use the character “A”, which replaced the previous symbol “Ar”. This change is merely formal – technical requirement described with this parameter has not changed.

The EN 13888:2009 standard specifies requirements for two types of grouts:
• CG – cement mortars,
• RG – mortars based on reactive resins.

Cement grout (“CG” symbol on the packaging)

Cement mortars may belong to different classes corresponding with certain basic or additional requirements provided by the standard. Classes are labeled with the numbers:
• 1 – grouts of standard bonding strength,
• 2 – grouts of enhanced parameters.

In case of grouts of enhanced parameters, additional letter labeling is also in use – it indicates the compliance with aforementioned additional requirements:
• A – in case of mortars of increased resistance to abrasion,
• W – in case of mortars with reduced water absorption.
 
The following are the possible combinations of grouts labeling, in accordance to EN 13888:2009:

Table 1. Labeling of the cement grouts (CG)

Grouts based on reactive resins (RG)

In contrast to the cement mortars, the standard does not provide a division into additional classes or types in case of mortars based on reactive resins. The current standard requirements for the mortars of this type are included in the EN 13888:2009 standard (no change in comparison to the previous standard).

Mortars based on reactive resins are manufactured as two-component products. The ingredients are packed separately and mixed immediately before use. The ingredient containing binder (usually an epoxy resin), aggregate and additives is in the form of dense, semi-dry mass. The second component – so-called hardener, is in the form of thick liquid. Its objective is to activate the chemical reactions causing the binder bonding.

Mortars of this type are more expensive than the cement – based ones. However, more favorable technical parameters compensate the higher price. In comparison to the cement mortars, the mortars based on reactive resins are above all more durable, they also have higher mechanical strength and hardness. The joint surface is practically nonabsorbent and has very high resistance to dirt. These properties provide very high joints resistance against the influence of the room operations – walking, vehicles movement, washing and cleaning as well as resistance to chemicals – acids, moderately aggressive chemicals, strong detergents and disinfectants.

Criteria for selecting grouts
When selecting appropriate grout one should consider the following criteria:

–          Type of cladding to be grouted (CG2WA grout is suitable for all types of cladding),

–          Technical function and location of the joint:
• indoors, outdoors,
• volume of traffic, facility type ,
• substrate deformability, under floor or wall heating, terrace or balcony,
• protection against moisture and water in bathrooms, showers, swimming pools, terraces, balconies,
• presence of dirt; workshops, garages,
• resistance to fungi, moulds in areas of high humidity and temperature, for example in shower cabins and wet zones in bathrooms,
• resistance to bacterial growth, for example in food processing, laboratories.

The CG 1 and CG 2 type of cement mortars is recommended for indoor use only, in residential buildings and other of little traffic. The CG 2 cement mortars can be used on surfaces with underfloor or wall heating. It is recommended to use only the CG 2 type of mortars with additional features, i.e. reduced water absorption and/or increased resistance to abrasion, outdoors, on terraces, balconies and stairs. The RG type of mortars is recommended for grouting in industrial and food processing facilities, car washes, swimming pools, hospitals, etc. as well as in bathrooms, shower cubicles and kitchens in residential buildings (especially in places where the cladding is exposed to stains of grease, coffee and juice). The RG mortars perform excellent in the public access buildings, shops and at areas of intensive traffic. The RG mortars are not recommended for use on terraces and balconies because of their characteristics.

Aesthetics of the grouts:
• change of thegrout colour due to the operation influence,
• floor, wall.

Factors associated with the operation of the cladding can cause gradual change of the colour and the appearance. For this reason, it is recommended to consider the place of application already at the stage of selecting the grout colour. It is reasonable to apply grouts of darker colours on floors as they get less dirty. The colour of grout on the walls and decorative elements can be fairly brighter. It is absolutely recommended to use dark grouts in the utility rooms, warehouses, garages, etc.

Selecting the grouts in view of grouts width

Recommendations regarding the selection of joint widths are shown in the table.

Tab. 2. Recommended joint widths (according to the ITB Instruction No. 397/2004).

In practice, the selection of joint width should be made considering the tiles location and the technology of tiles manufacturing. The joints should be wider when they concern outdoor surfaces. In case of calibrated tiles, one can apply a narrow joint (in view of technical function of the grout one cannot fix the tiles without any grout between them).

The ITB instruction is not a document that has the status of a standard – in other words it does not impose any mandatory compliance. The contractors may execute the work according to ITB instruction but they do not have to. So, it is worth taking a closer look at the grouts offer of manufacturers which produce various types of grouting mortars. Most often, one can find a division into the “tight” grouts (from 1 mm to 6 mm) and so-called “wide” grouts for use in the joints from 4 up to 25 mm. Less frequently, one can find a mortar of general use, e.g. from 1 to 25 mm of designed width. Although, it must be noted that such solution is very beneficial as it enables to use the same mortar for large floor tiles, smaller wall tiles and tiny mosaic or decorative elements, for example in the zone of mirrors.

Consumption of the grout may be calculated using the formula: (A+B)/(A*B)*C*D*g = ?? kg/m²

where:
A – dimension of a tile, length in mm,
B – dimension of a tile, width in mm,
C – thickness of a tile in mm,
D – width of the joint in mm,
g – consumption ratio (1.5 kg for cement-based grout, 1.6 for reactive epoxy grout).

Agents for cleaning, maintenance and waterproofing of cladding
Agents can be divided into:
• Cleaners to remove dirt and residues of cement mortars, debris left by the minerals contained in water, limestone from:

– ceramic and milled rock tiles, sanitary facilities,
– natural stone,
– metals and plastics.

• Cleaners to remove residues and polymer dirt of paints, dispersion renders and from the surfaces as above.
• Impregnating agents (impregnants) to protect absorbent surfaces and those with open pores from the absorption of damp, dirt from oils, coffee, tea, and to facilitate the subsequent cleaning.

– for unglazed ceramic tiles,
– for milled rock tiles,
– for natural stone,
– for cement joints.

• Agents for waterproofing and protecting absorbent surfaces and absorbent mineral plasters, ceramic tiles, stone and cement mortars against the water penetration and environmental impact. We obtain the impression of beading on the surface of impregnated materials.

• Grout renovator to renovate, unify, and change the colour of the cement joint.

Original text: AtlasFachowca.pl

English text: Piotr Marciniak, ATLAS Group