external cladding, façades - ipc...materials and movement joints shall be the essential elements of...

EXTERNAL CLADDING, FAÇADES

The façade of a building, considered as an envelope overlooking publicly trafficked areas, always represents an outstanding element of the architectonic project that usually receives enough attention. Apart from the functional requirements common in any envelope, we must take into account the aesthetic aspects that sometimes entail the high standards regarding the corporate image of a firm, symbol of the social status of a community or identification of the owner’s personality.

In the past, the function of envelopes was to separate the internal and external areas of a building, sometimes with an added structural function. Industrialized building construction brought in new materials and building construction techniques, aimed at increasing the performance of the construction process as well as at satisfying bigger functional requirements in envelopes. Those functional requirements may be summarised in:

► Protection of the rest of the construction elements of the building and extension of their service life.

► Waterproofing and good vapour diffusion performance.

► Thermal and acoustic insulation.► Minimization of maintenance and cleaning costs,

considering the value of replacement and installation of new materials.

Therefore, once the functional structure of an envelope decreases or disappears, we have a large set of functional requirements that have evolved throughout time with the aim of achieving higher levels of habitat quality. Envelopes exposed to the visual environment must also satisfy certain aesthetic determining factors not only related to the owner’s will and personality but also to cultural idiosyncrasy and respect towards the rural or urban environment.

Functions of envelopes

The aim of the diagram below is to show, via its headings, the functions of an envelope. The complexity of this construction element shown in the diagram has led to the constant evolution of standards regarding both materials and construction techniques. Fast technological changes introduced in the last two decades have led to a permanent revision of standards; hence references to specifications older than five years are considered obsolete. In this context, ceramic tiles in external claddings start to be used again thanks to a constant will of adaptation to the materials and construction techniques that have been introduced lately:

Non-conventional coverings 1External cladding, façades

► Direct installation on the envelopes, even innovating ones, securing bonding and then deformability. Constant evolution of grouting materials, from the first cementitious adhesive compositions with rubber and dispersion polymers (the 50’s). Besides, consideration of vapour diffusion through tile-to-tile joints and optimization of the characteristics of grouting materials.

► Evolution in the alternative solutions and proposals to direct installation on envelopes, from the implementation of curtain wall and its subsequent spreading. Mechanical anchoring appears.

► Construction solutions for the installation of ceramic tiles on multilayer systems with insulation.

► Fast evolution of prefabricated systems (multifunction panels with mechanical anchoring), including ceramic cladding on their fair face.


The future of ceramic tiles in external claddings depends to a great extent on their adaptation to substrates and to those functional requirements, considered as a whole. Hence the importance in the consideration and adoption of techniques and materials compatible with the substrates and the multilayer system in charge of satisfactorily fulfil the functional requirements.

Ceramic cladding shall be the epidermis of this envelope system, thanks to its contribution to impermeability and its inalterability to all kind of external actions.

Let us see some of the functional requirements of the multilayer system in more detail.

Structural adaptation

A building is subject to different movements whose origin is either intrinsic to the building itself or induced from external sources, that is:

► Maturity shrinkage of construction elements.► Settling of structure.► Weight of the construction elements.► Live and dead loads.► Thermal and, to a lesser extent, hygroscopic expansion and contraction.► Wind pressure and depression.► Movements with a seismic origin.


Detail of the external façade of the Hachioji City Art & Cultural Hallbuilding (Ichou Hall, Tokyo, Japan). Glazed ceramic tiles with a size of 73.1x73.1 cm and 51.3x51.3 cm, both 16 mm thick. Tile & Architecture, no. 15, INAX CORPORATION.

Foreseeing the weight of these movements shall be a part of the project; envelopes shall be designed and executed in accordance with that forecast. Selection of materials and movement joints shall be the essential elements of structural adaptation. Ceramic claddings will be dumb witnesses of these movements, with the only and humble contribution of tile-to-tile joints.


Possible movements in a building. LATICRETE® documentation

Effects of drying shrinkage and hardening of concrete floor slab

Building movements due to wind or seismic action

Protection against water action and external moisture

Now we are going to consider the role played by envelopes in the protection of buildings against water and external moisture. The former, in its different modalities (water, snow and ice) and intensity, with or without wind; the latter, coming from the external air environment or from the terrestrial medium and transmitted through capillarity of construction elements.

Both the design of the envelope and the selection of the most suitable materials shall be determined by the forecast regarding the modality and intensity of the actions of water and moisture. This forecast shall take into account the weather conditions in the building environment, as well as its height and orientation. Some countries have established categories to assess the action of water. The German standard DIN 4108, Part 3, Section 4, establishes this type of classification:

► Stress Group I, for buildings in geographic areas with rainfall below 600 mm or higher than that annual pluviometry but with zero or very moderate wind action.

► Stress Group II, for buildings in geographic areas with rainfall between 600 and 800 mm, and moderate winds. This group includes tall buildings and houses exposed to moderate torrential rain.

► Stress Group III, for buildings in geographic areas with annual average rainfall over 800 mm, and risk of torrential rain, with important role of wind action (although rainfall is smaller than that quantity).

According to this classification of the importance of water action, ceramic claddings installed with cement mortar, both in the modalities of ventilated envelope at the back and direct fixing, meet the requirements demanded from the three groups. Installation on a plaster layer and waterproof grouting are compulsory for group III.

Installation with cementitious adhesives, as long as executed under quality premises, secures optimal performance against water action.

At this point we must be aware that:

► Porous and glazed tiles and non porous ones are waterproof, but under no circumstances must we consider the ceramic cladding waterproof as a whole, only considering the type of ceramic tile.

► Movement and tile-to-tile joints must be waterproof for the combined effect of the selection of materials and the execution technique.

► Waterproofing shall be achieved by other means if special securing is required. In any case, external claddings require vapour diffusion capacity from the inside, incompatible with waterproofing unless there is a diffusion channel before such waterproofing, i.e. placing intermediate ventilation between the internal envelope and the waterproofing.


Frost risk must be added to direct action of water if water is able to enter the envelope, at any level, and freezes. Foreseeing frost risk in ceramic claddings is essential to keep both the fair face and the inside part inalterable, as the mechanical action of ice shall be progressive in time and to the extent that necessary surface waterproofing is altered. In geographic areas with frost risk, as defined at the functional classification of ceramic tiles documentary block, we will decide:

► The selection of ceramic tiles with open porosity smaller than 3% and passing the resistance to freezing test method (ISO 10.545-12).

► The selection of waterproof grouts and execution that avoids the presence of cracks and openings in tile-to-tile joints.

► The full tightness of movement joints and the junctures of the ceramic cladding and other materials and construction elements.

► To avoid the production of moisture and water vapour condensations from the interior of the building or from the terrain on to the bonding material or any of the intermediate layers on top of the fixing substrate.

Moisture coming from the ground or from other construction elements shall be removed by installing the corresponding waterproofing.

The action of hail, as mechanical aggression through impact, may be considered totally irrelevant in the case of ceramic claddings. However, this is not the case of other materials in which an evident mechanical damage or even rupture can take place.

Vapour diffusion and condensation water disposal

Environment humidity always goes from the area with the highest vapour pressure to the area with the smallest pressure. In winter, this humidity circulates from the inside (higher temperature and therefore possibility of higher vapour pressure) to the outside, which can lead to the production of condensations at any point of the envelope where the dew point temperature is reached (see section ceramic coverings on thermal insulation). These condensations may result in damage of the materials, creation of organic crops or destructive action of ice if that condensation water freezes.

These negative actions of moisture/water caused by vapour diffusion are avoided if free circulation outwards is allowed so that vapour can enter the air. Likewise, a barrier can be placed in order to prevent the presence of condensations, or if even so condensations occur, they can be conveniently drained.

Glazed ceramic tiles and those ones with low porosity are completely impervious to vapour diffusion. Therefore, if we require suitable diffusion of water vapour through the envelope with a ceramic cladding we will consider tile-to-tile joints.

Apart from contributing to reduce the mechanical rigidity of ceramic claddings, tile-to-tile joints have the property of diffusing the water vapour arriving at the back side of the ceramic tile.

It is admitted that a participation of 5% of the surface of tile-to-tile joints on the total surface of the ceramic cladding can guarantee the correct vapour diffusion in normal conditions of pressure and internal/external temperature jump. This 5% of


participation is not an irrelevant percentage: Ceramic claddings with 30 x 30 cm tiles shall require tile-to-tile joints wider than 6 mm in order to reach that percentage; on the other hand, the use of 25 x 25 mm ceramic mosaic, fixed with a 1.5 mm joint shall reach 11% in the ratio between the surface of the joints and the total surface of the cladding.

Therefore, in ceramic claddings requiring vapour diffusion we will secure a joint size/width ratio that allows a percentage of contribution of the surface of tile-to-tile joints bigger than that 5% regarding the total surface.

Expansion/shrinkage movements due to hygroscopic and thermal action

As you can see from the following chart, most materials used in an envelope, from ceramic ones to mortars, have moderate linear thermal expansion coefficients. Important differences take place between those materials and metals, and especially between those materials and organic-based materials, which has to be taken into account when sealing the joint at the juncture with that kind of materials (e.g. junctures with aluminium and PVC frames).

Considering an envelope clad with dark ceramic tiles exposed to high thermal variations in a specific time interval (e.g. reaching a temperature of 70ºC after strong insolation and going down to -10ºC at a frosty night) we will have dimensional variations of around several tenths of millimetre per linear metre.

On the other hand, the ratio between expansion coefficient of ceramic tiles and other materials involved in installation is usually in the proportion 1:2 (granulated concrete) or 1:4 (aluminium). Since lower layers will be at a lower temperature, there may be certain compensation that relieves shear forces between layers.


COEFFICIENTS OF LINEAR THERMAL EXPANSION OF DIFFERENT MATERIALS

Materials Coefficient of linear thermal expansion (x 10-6 ºC-1)

Ceramic tiles 4-8Natural stone

GraniteMarble, travertineQuartzite, porphyry

8-104-79-12

Masonry materialsCement mortarGypsumConcrete blocksCellular concrete blocksBricks

10-1318-216-128-125-8

ConcretesConcreteAir-entrained concreteLightweight concreteConcrete with vermiculite or pearlite

10-138

8-126-8

MetalsSteelAluminiumCopperBronzeIron and cast ironLead

10-182417201030

Asphalt 30-80Organic materials

ThermoplasticsPVCPolyethylenePolystyrene

CellularPVCPURPolystyrene

40-70110-20060-80

35-5020-7015-45

Glass 5-8Wood

Parallel to the fibresAt right angles to the fibres

4-630-70

The prefabrication system with ventilated walls allows greater homogeneity in the movement of materials, since the differences in coefficients are compensated with the important difference of temperature between the fair face of tiles and the back side of the panel adjoining the ventilated conduct.

The mechanical strength of materials does not change with important thermal oscillations. In cementitious adhesives with polymers and grouting materials of the same nature we must know the interval of temperatures without alterations of their essential characteristics (adhesion and deformability). Grouting materials should be unalterable to long exposure to ultraviolet rays from solar radiation.


Long periods of moisture affecting the whole multilayer system should not take place if a ceramic cladding has been accurately executed on an envelope meeting all the quality requirements. This situation contradicts all the above said, regarding both protection against water and vapour diffusion. Nevertheless, it must be known that the expanding action due to water imbibition in ceramic materials, especially those we will be regularly using in (low porosity) envelopes, is zero or very small (always below 0.6 mm per linear metre). The same can be said of bonding and grouting materials and current insulation systems usually of the closed-cell type, and therefore, impervious (c.a.a<0.2%). When considering the hygroscopic expansion variable, the maximum expansion expected shall be added to the maximum values of thermal movement; the result shall provide us with the necessary data to design tile-to-tile joints and, especially, the location and characteristics of movement joints.

Regarding ceramic tiles and installation of ceramic claddings we must recommend:

► Selection of small or medium-sized (≤30x30 cm) ceramic tiles, with moderate water absorption capacity and, if possible, with light colours as a precaution against large thermal differences.

► Tile-to-tile joints accurately sized to the expected movements; the width of these joints shall never be smaller than 3mm. The width designed shall be in accordance with the size and thickness of the ceramic tile, the bonding and grouting materials selected and the performance of the multilayer system placed behind the ceramic cladding or the metal frames, in the case of prefabricated panels. Designing 6.8 and 10 mm tile-to-tile joints for external claddings with a nominal size larger than 20x20 cm is a common practice.


Lengthening of three 10-metre long materials for an increase of temperature of 80ºC

► Suitable movement joints to absorb ceramic cladding stresses. Intermediate joints usually mark the limits of stretches of 3 m of maximum horizontal distance and 6 m of maximum distance between vertical joints. Sealing materials are required to have optimal characteristics regarding waterproofing, lateral adherence and inalterability to UV light; at least, we must select those ones with longer ageing. Since the service life of these materials is usually between 10 and 20 years it is recommendable to foresee, in the design stage, the most suitable system allowing easy and fast refurbishment (at the lowest cost possible) in the foreseeable replacements that will take place throughout the service life of the building.

► Solving the junctures with other construction elements, with other materials and with wood and metal work by making use, if possible, of ceramic juncture trims (angles, dripstone, coves,…) and sealing those junctures accurately.

Installation techniques

As far as ceramic claddings of envelopes are concerned, a large number of materials and techniques are involved, due to the functional complexity of this type of construction elements and the other requirements dealing with design and adaptation to budget. In a rough way, the following classification can be established:

► Direct installation onto the envelope acting as substrate. In this case, the envelope is required to have good mechanical strength, no efflorescences, nor continuous cracks, unclosed holes or similar defects.

► Installation of the ceramic cladding onto a thermal insulation layer, with a reinforced plaster layer in-between.

► Installation of prefabricated construction elements made from concrete clad with ceramic tiles that, in turn, may have different multilayer systems, including thermal insulation and air chamber in the ventilated wall modality.

► Mechanical anchoring of ceramic tiles, usually big ones, over a structure that grants the group with the ventilated wall modality.


In turn, variations can be established within each group according to functional requirements, type of construction and also the budget of the work. Although Central Europe has an extensive body of standards regulating the different modalities of execution of external claddings, in many cases we are dealing with an emerging technology which is not standardized yet. Every country has their own national standards on security and functionality of envelopes. In our country, this topic is still new, at least regarding functionality aspects.

Let us see here the most common case of direct anchoring on the envelope or over intermediate thermal insulation, breaking down the different layers of the multilayer system.

In sections below we make reference to the mechanical anchoring of large ceramic tiles and to prefabrication of panels, which is a technology poorly developed in Europe but widely spread at present throughout the whole Pacific Area, with epicentres in Japan and, to a lesser extent, in the West Coast of the United States of America.

Preparation of the fixing substrate

Direct installation of a ceramic cladding shall require a stable mature envelope, with the suitable mechanical strength, no cracks nor efflorescences. Additionally, all hollow spaces and holes or similar defects shall have been accurately filled.

After that, the next step to take place is surface control and thorough cleaning of the whole fixing substrate. This process shall result in a dust-free surface, with no rests of formwork, mortar or gypsum spots, dirt, grease, etc.

Once the fixing surface is clean, a hemp cord or wire net is carefully installed, both horizontally and vertically, in order to establish the vertical fixing plane and the departures from planarity of the envelope fair face.


Continuous thermal insulation on the façade of a building with extruded polystyrene foam rigid sheets. DOW CHEMICAL IBÉRICA, S.A.

Installation of prefabricated panels. CERAMIC TILE FROM JAPAN. EXTERIOR TILE. VOL. 1

Ventilated façade with porcelain tile over auxiliary structure. TAU CERÁMICA

If departures from planarity are bigger than 20 mm measured with a 2-metre straightedge, in all directions, we will make use of a regularising layer irrespectively of other considerations and in any installation method. This regularising layer shall always be necessary when using the thin-bed installation technique.

A rough plaster or sprayed or brush parge coat is always applied on the already prepared envelope surface. This coating prepares the bonding of the following layers or direct thick-bed installation of ceramic tiles if we have the suitable planarity.

For this rough plaster we will use dry mortars in the volumetric proportion cement/sand of 1:2 or 1:3, with sand of particle size distribution Ø 0-4 mm. The use of cement-lime mortars is not recommended in any case, as lime may produce efflorescences at the joints and in certain types of ceramic tiles; it can even lead to the destruction of cladding due to salt crystallization. We can use cement of the CEM I or II/32.5 (RC/97) or CEM I or II/42.5 (RC/97) types.

Prior to the application of the rough plaster, the pre-existing structural joints shall have been cleaned and protected. These joints shall be continued in all their width and length in the whole multilayer system of the ceramic cladding.

The maximum thickness of this sprayed parge coat shall be 100 mm and the following task shall not be undertaken until setting is completed.

It is advisable to wet the envelope before applying the sprayed parge coat in the event of strong insolation or heavy winds.

Regularising layer

In the following situations it will be necessary the execution of a regularising layer that, in some cases, acts as a levelling layer and, in others, also as additional anchoring and stress distribution (reinforced regularising layer):

► Thin-bed installation with departures from planarity bigger than 3 mm in 2 m ► If the envelope is exposed to strong torrential rains (stress group III,

according to DIN 4108, Part 3). In this case, the mortar shall include a waterproof additive.

This regularising layer shall include reinforcement made of stainless steel mesh or wire mesh of 50x50 mm of mesh light and 2 mm Ø rod placed in the middle of the layer and with direct mechanical anchoring on the substrate, in the following cases:

► When the layer must exceed the 25 mm maximum thickness at some part of the envelope.

► If the envelope is formed by different materials, or differential movements are expected.

► If we have to clad very smooth surfaces (e.g. concrete elements obtained from steel formwork).

► If thermal insulation is installed over the envelope.


The regularising layer is executed with cement mortar in a volumetric ratio of 1:3 to 1:4, preferably using CEM I ó II/42.5 (RC/97) cement and the trass (TrZ) variety and sand with 0-4 mm Ø granulometry.

This regularising layer shall have a minimum thickness of 10 mm and a maximum one of 25 mm. The use of reinforcement is necessary in case of bigger thickness.

When installing the lath, the regularising layer shall be applied in two stages. The first step consists in executing the mechanical anchoring of the mesh. These fastenings shall be of the type represented in the picture attached, placing the slot in the central position of the thickness of the regularising layer. Once this operation is finished, a first mortar layer shall be applied, flush with the slot, and once the lath has been installed we will proceed to extend the second layer until the required thickness is completed. The second layer shall be executed between 4 and 24 hours after having finished the first one.

The finish and planarity of this regularising layer shall be in accordance with the installation technique selected. With thin-bed installation, planarity departures of 2mm, measured with a 2 metre straightedge in all directions of the plane, will be allowed.

Both reinforcement lath and regularising layer shall be interrupted when meeting all the movement joints.

The following schemes show two construction sections of ceramic claddings with and without reinforcement lath.


Stainless steel anchoring with slot for hanging the reinforcement. Source: PRAXIS-HANDBUCH FLIESEN, de Ernest Ulrich Niemer.

Thermal insulation

If a thermal insulation system is adopted on the outside of the envelope, closed-cell (practically unabsorbing) highly compression-resistant thermal insulating materials, with tongue and groove joints will be used in order to obtain continuous insulation with no thermal bridges. Insulating sheets, which will be fastened to the envelope with flexoelastic fasteners, will be covered by a regularising layer, with a thickness of between 25 and 35 mm, also with reinforcement fastened to the envelope.

The German standard DIN 18.515, in its section 7.3, provides information on the distance of anchoring in a thermal insulated external cladding. Scheme A shows an accurate distribution for a stretch limited by intermediate movement joints (6x3 m); in scheme B we can see a construction section of an external ceramic cladding with thermal insulation.

In the event of surface irregularities or lack of planarity of the envelope, we will install a regularising layer prior to the installation of the thermal insulating material. Planarity must be obtained on this layer, within the admitted tolerances, never on the reinforced plaster over the insulation.

Ceramic tiles

In principle, external ceramic claddings may be executed with any type of ceramic tiles. However, some restrictions of use are imposed by functional requirements, securement of bonding and environmental conditions:

► With the aim of securing both easiness of cleaning and zero maintenance, we will choose glazed tiles or low porosity tiles.

► It is sensible to establish a limit for the size and thickness of the ceramic tile with the aim of securing bonding, either of the mechanical and/or chemical type. Standard DIN 18515, Part 1, establishes that limit in ceramic tiles with a surface equivalent to 30x40 cm (1200 cm2 of surface, bigger side of 40 cm


Source: PRAXIS-HANDBUCH FLIESEN, de Ernest Ulrich Niemer.

Scheme A Scheme B

and 15 mm thickness, without counting relief on the fair face). For bigger thickness and sizes, mechanical anchoring installation is proposed.

► In ceramic claddings in geographic areas with frost risk we will use ceramic tiles with open porosity smaller than 3%. These tiles must pass the test method proposed in standard 10545-12.

► In external ceramic claddings, we will never use ceramic tiles premounted on mesh backing, to avoid jeopardising bonding (no bonding material shall be in contact with the tile in the area occupied by the mesh!).

► We will choose light colours in highly insolated areas.

For external ceramic claddings, it is recommended to use medium-sized ceramic tiles no bigger than 30x30 cm. This will guarantee:

- Good handling of ceramic product in installation.- Commitment between bonding and weight of the tile, in this case with shear

strength.- Suitable elasticity of the ceramic cladding with no need of oversizing tile-to-

tile joints.- If necessary, favouring suitable vapour diffusion with tile-to-tile joints no

wider than 8 mm.

Thin-bed installation

In ceramic claddings with low porosity tiles and in those cases requiring special bonding and elasticity properties, the thin-bed installation technique shall be applied, preferably with the use of C 2 deformable adhesives. In no case shall D 1, D 2 adhesive pastes be used in external claddings.

This installation technique requires smaller planarity deviations, hence we will need well screeded regularising layers (maximum tolerances of 2 mm in 2 m) or use cementitious adhesives allowing thickness over 5 mm with no bonding reduction. Standard DIN 18157, Part 1, regulates thin-bed tile installation with hydraulic hardening mortars, under the following conditions:

► Installation shall be carried out if ambient temperature is 5ºC or over.► Surfaces to be clad must not be moistened.► In the event of strong insolation or wind, the applied surface shall be reduced

so that all the tiles are placed within the margin, now reduced, of open time.► Manufacturer’s instructions shall be scrupulously followed regarding: mixing

and wedging, standing times, time of use (service life), open time and set up time.

► The selection of the cog trowel shall depend on the size of the tile, according to the following chart.


SELECTION OF THE TYPE OF COG TROWEL ACCORDING TO THE SIZE OF THE TILE

SIZE (MM) DEPTH OF THE COG (MM)

Up to50 x 50> 50 to 108> 108 to 200

> 200

3468

Thin-bed installation of external ceramic claddings requires the use of double gluing in all the cases if tiles are bigger than 10 x 10 cm. This method consists in spreading the cementitious adhesive, on a homogeneous layer, over the backside of the tile. For this operation we will use the sharp edge of the cog trowel. The tile with the adhesive on its backside shall be placed, with an upwards and downwards movement, on the grooves of the adhesive previously applied on the fixing substrate. If the thickness of the bonding layer must be precisely preserved, it is also advisable to comb the backside of the tile, crossing the grooves in the fixing operation. Corrections and adjustments must be carried out immediately after installation, or at least, within the time allowed.

The wetting capacity of the adhesive shall be periodically checked (every square metre installed). This capacity shall always be bigger than 75% of the tile surface. Checking this shall guarantee that we have installed the tiles within the open time of the adhesive. If the surface that gets dirty with the adhesive is smaller than 3/4 parts, we will remove the material and add a new dose, combing it again with the cog trowel.

Tile bonding may be seriously jeopardized if the open time is not observed , with the responsibility and damage this involves in external cladding. It is advisable to cancel installation in the event of strong winds and/or temperatures over 30 ºC.

When the adhesive is semi-hardened, we will touch up the tile-to-tile joints to obtain a uniform section prior to the following grouting operation.

Tile-to-tile joints

Prior to proceeding to the grouting operation, tile-to-tile joints must remain clean, if necessary with the help of a tool that allows the removal of loose materials. This tool may be the same that we use when touching up the joints once the fixing operation is completed, set up time expired.

Tile-to-tile joints represent an essential part in the quality and good performance of the envelope in external ceramic claddings. Any defect, especially hollows in the grouting material and shrinkage cracks, may result in the beginning of damage that will affect the whole cladding system. It is essential the accurate selection of the grouting material; e.g. an inaccurate granulometry of the aggregate may result in cracks and poor bonding of the material.

It has already been stated the importance of dimensioning the width of tile-to-tile joints accurately, for both their contribution to the elasticity of the ceramic cladding and their role in the diffusion of vapour water, if the latter function is required (remember


that the participation of the joint in the total surface of the ceramic cladding must be at least 5% to guarantee accurate vapour diffusion).

Tile-to-tile joints shall reject rainwater, being therefore waterproof. This requirement is not in contradiction with vapour diffusion capacity, since water is in different states. Therefore, we will demand waterproof grouts and, at the same time, guaranteed capacity for vapour diffusion. Other important properties have to do with bonding, elasticity and resistance of the colour of the joint to ultraviolet rays, as well as moderate chemical resistance (taking into account atmospheric pollution and the possibility of acid rain). The manufacturer of grouting materials must expressly certify the suitability of the product for external ceramic claddings. In turn, the tile fixer shall scrupulously observe the manufacturer’s instructions and recommendations.

It is advisable the systematic execution of tile-to-tile joints, paying attention to both controlling the accurate filling of the joints and the total cleaning and finish of the ceramic cladding, given the special circumstances surrounding external ceramic claddings. The tile fixer shall have into account the hardening time and start cleaning within the terms recommended by the manufacturer.

In the event of strong insolation or wind we will have to assess if it is advisable or not to carry out the grouting operation, always within the interval of temperatures in which the grouting material can be applied.

In the case of external ceramic claddings we can find either a finish aligned with the surface of the tile or a reproduction of the typical concave curvature of internal ceramic claddings.

Movement joints

This semi construction element represents the essential factor regarding mobility of the ceramic cladding before all its movements, both those typical of the building and those induced, which can take place in the envelope. Movement joints will contribute to the reduction of dangerous stresses that can be transmitted to the ceramic tile, provoking its breakage or detachment.

The importance of movement joints necessarily leads to taking action already in the designing stage, with the selection of the type of joint, materials to be used and layout in the envelopes. As an example, we provide graphic documents on the layout of movement joints in the façade of a building, as well as the construction characteristics at the junctures with the structure (perimeter closures and slabs), juncture with metal or wood work and graphic expression of the construction detail of a joint, all of which based on documents by SISTEMAS LATICRETE, S.A.. The first picture shows the distribution of movement joints in a block of flats; horizontal joints coincide with the lower part of the slab on each floor and the vertical ones linked to the hollows of the envelope.

Already in the designing stage, definition of the materials to be used in each case is compulsory. Sealing materials must allow movement absorption between 20 and 25% of the joint width. Stress, with 100% movement absorption, must not exceed 0.2 N/mm2. Materials for movement joints must also be waterproof and resistant to both


solar radiation and working temperature of the envelope, as well as chemical resistance adapted to ambient pollution.

Firstly, we will have structural movement joints coinciding with the pre-existing joints on the envelope, which we will observe in all their width and length. Secondly, we will have perimeter joints, which in this case will coincide with the building floors and the changes of plane of the envelope. Thirdly, we will have intermediate joints, which will be placed according to the needs, already in the designing stage. The second and third types of joints must go through and reach the substrate or, at least, the sprayed parge coat.

For intermediate joints it is common practice to observe the distance between the lower part of two consecutive slabs in horizontal ones and lay out the vertical ones at a distance of between 3 and 6 m, fitting them, as much as possible, with the hollows aligned.

Perimeter joints may be placed at the corners or at a certain distance from these corners. Of course, perimeter joints will be included in any change of plane of the envelope or at the level where materials change, when such materials present different performance regarding movement.


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