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Fast track installation of ceramic tiling

Introduction
Where building programmes are short and/or cost penalties high, the designer has to take advantage of every material and technique that allows ceramic tiling to be installed and serviceable within the contract time. Fast track installation of tiling can reduce the contract time by hours, days or even weeks as long as it is planned within the scope of works; and the increase in material cost is easily offset by the savings in time that can be achieved.

Objective
There are two basic areas relating to ceramic tiling that can be considered appropriate for “fast track” working. The first relates to a completely new installation, i.e. the construction of the background and the installation of the ceramic tiles within a limited time period, thus achieving early completion. The second relates to the installation of the ceramic tiles to an existing area so that the location can be put back into use without undue delay. Examples would include station platforms, fire stations, retail outlets that are trading, car showrooms, etc.
The installation of rigid finishes such as ceramic tiles using normal techniques places constraints on the time taken to complete the installation, not only with new build projects but also with refurbishment projects. This is due to the fact that rigid finishes require that the background is stable and in particular has finished undergoing shrinkage. Shrinkage is a phenomenon that is characteristic of cement-based materials such as concrete, screeds and render but also applies to gypsum plasters, blockwork walls, etc., and all backgrounds that frequently require tiling. Shrinkage of such materials can take weeks or months to complete; time scales that are not commensurate with “fast track” working. This paper is intended to give an overview of techniques and materials that can be used to overcome the fundamental problem of reconciling long term shrinkage with “fast track” working.
Fast track work in ceramic tiling can be defined as the installation of ceramic tiles so that the installed ceramic tiling can be in use in a shorter period of time than would be achieved using normal materials and conventional techniques. Many fast track installations are in critical situations where it is essential to get it right first time, as it may not be practicable to easily carry out repairs if problems subsequently occur.
There are advantages in the completion of a construction project within a set time and in the commercial sector the earlier the building is in use and earning money the better it is for the client’s finances. Obviously the shorter the construction times the greater the advantages. This applies just as much to the refurbishment projects and early completion can be even more advantageous if the circumstances require the complete closure of an existing facility. There are limits however; these can be practical difficulties of having too many people working in one location at the same time; the temperature on site being too low and other conditions that cannot be controlled. Similarly using a rapid hardening adhesive to save a few hours may not achieve the objective if 3 weeks have had to elapse for the screed to finish drying and shrinking.

Normal constraints
Before considering the possibilities of shortening the tile installation times it is worthwhile to outline the conventional constraints that apply to normal ceramic tiling. If new backgrounds installed to receive the ceramic tiles are subject to drying shrinkage then most of this shrinkage should take place before the ceramic tiling is adhered to the background. Note that where new backgrounds are constructed of several separate applications of materials the drying times of each application are cumulative and not concurrent.
A typical example would be a wall constructed of concrete blockwork that has to dry for at least 6 weeks before the first coat of cement and sand render is applied. If more than one coat of render is to be applied the first coat of render should be cured for a few days (prevent rapid drying of the surface) before being allowed to dry, shrink and harden before the next coat of render is applied. The final coat of render should be wood float finished and has to be cured for a few days and then allowed to dry for at least 2 weeks before the ceramic tiles are installed.
These cumulative drying times have to be considerably extended in adverse site conditions, as the drying and consequent shrinkage of the backgrounds will be very slow if the temperature of the background is low. Some European countries take a more realistic approach and the minimum drying times of backgrounds to receive adhered rigid finishes are considerably longer than those recommended in the British Standard Codes of Practice. For instance in Germany the drying time of concrete is accepted as taking 6 months whilst in the UK the British Standard gives a minimum of 6 weeks under good drying conditions. The key word here is “minimum”; it may take considerably longer under typical UK conditions!
Even where refurbishment work is carried out, either some new backgrounds have to be constructed or old backgrounds reconstructed and there will be delays caused by the required drying times of in situ applied backgrounds.

Potential problems
Ceramic tiles are characteristically hard and brittle, with a high Young’s modulus of elasticity. A slight lateral compression of the ceramic tiles can develop extremely high levels of stress particularly where the ceramic tiles are fixed with adhesives since adhesion to strong backgrounds is usually good. If the stresses exceed the restraint between the tile and the background the ceramic tiles will debond with the ceramic tiles bulging out from the background. The amount of bulging out or debonding may be only slight but tends to occur away from movement joints as the stresses tend to be more concentrated in the centre of an area of ceramic tiling.
If the correct design criteria are not addressed, or if the materials used to install the ceramic tiling do not have the necessary properties, then problems can occur with the installed ceramic tiling. Background shrinkage after the ceramic tiles have been installed is the most common cause of problems with ceramic tiling where not enough time has been allowed for the background to dry sufficiently before the ceramic tiles were installed.
The problems usually do not occur until several months or even a few years have elapsed after the installation had been completed; though under certain conditions some problems have shown up even before the contract had been completed. The heating up of the building after completion can cause renewed background shrinkage, as drying down to a moisture content in equilibrium with the warmer and drier conditions will occur.
The rapid increase in the use of underfloor heating, either embedded in the underlying screed or with some refurbishment systems within the tile adhesive bed itself, has added to the potential problems both in terms of the conditioning required to stabilise the system and in respect of the consequent thermal cycling from the use of the heating system.
When the backgrounds continue to shrink (and expand with underfloor heating) after the ceramic tiles have been fixed the installed ceramic tiling is laterally compressed and such stresses are not relieved by the insertion of so-called stress relieving joints in the tile bed. With weakly adhered ceramic tiles, such as those fixed with cement and sand mortar, the stresses can result in the tile bed debonding at the stress relieving joints.

Prefabricated backgrounds
The use of certain prefabricated backgrounds, such as wood-based sheets and boards, can present problems as such boards will not be dimensionally stable with the moisture content of such boards fluctuating as the atmospheric humidity rises and falls. Ceramic tiling on one side of such boards essentially produces an unbalanced construction and if the board absorbs atmospheric humidity, or more frequently dries after the installation of the ceramic tiles, warping will occur with the likelihood of cracks developing at the board joints.
The recommendations in the British Standard Codes of Practice to have dry wood-based boards, with the backs and edges sealed to prevent the ingress of atmospheric humidity and rigidly fixed and braced, is difficult to achieve in practice. The conditioning of the wood-based boards, by drying them down to the moisture content that matches the long-term moisture content of the boards once the building is in use, can be difficult to achieve, particularly if the building is subsequently heated. Note that certain building boards that are not wood-based may also show dimensional changes with moisture content so they should also be conditioned to an appropriate moisture content before the ceramic tiles are fixed.

Solutions by design and materials
The problems of the required drying times can be by-passed by utilising certain design features and materials that overcome the inherent problems of using normal techniques to install the ceramic tiles. The selection of the background at the design stage can make a big difference by allowing the installation of the ceramic tiling to proceed almost as soon as the new backgrounds have been installed.
These design decisions can include the use of certain prefabricated backgrounds, such as stable boards on walls and rapid drying materials that dry and complete shrinking within hours rather than days. Materials such as ARDEX AM 100 one coat tiling render or a bonded ARDEX EB 2 rapid hardening floor screed will allow tiles to be fixed in hours rather than after weeks, even unbonded cement/sand screeds may be tiled after 24 hours if ARDEX A 35 rapid drying cement for floor screeds or ARDEX A 35 MIX rapid pre-blended rapid drying screed mortar are used. The decision to use rapid setting, rapid hardening and rapid drying adhesives and grouts will enable the ceramic tiles to be fixed and grouted within a very short time period.
The application, where appropriate, of paper-faced plasterboard is an effective solution for many internal walls in dry locations that are exposed to normal use as a background for ceramic tiling. In areas where the ceramic tiling is in wet and humid areas, such as showers, the use of proprietary boards specifically designed for supporting ceramic tiling in such locations will enable ceramic tiling to be fixed immediately after the installation of the boards. Or alternatively the use of waterproof coating systems such as ARDEX WPC flexible rapid drying and setting waterproof coating allows tiles to be fixed just 2 hours after the application of the second waterproof coat.
Where the ceramic tiling is designed to be installed on cement and sand screed over a new concrete base, then the decision to use ARDEX A 35 cement, a special proprietary rapid drying cement, to install the unbonded screed over an effective slip/damp-proof membrane on the concrete base will be effective.
The ARDEX A 35 cement will provide a screed that will have dried and shrunk sufficiently rapidly to enable the ceramic tiling to be installed just 24 hours later.
If an existing dry concrete base has to be tiled then it is possible to utilise a bonded screed made with ARDEX EB 2, a special proprietary rapid setting and hardening cement, so that the ceramic tiling can be installed just a few hours later. This system has the advantage that it may be used in wet locations including swimming pool surrounds and even in the pool itself. Adequate preparation of the concrete base and effective bonding of the screed should be specified to ensure good adhesion between the bonded screed and the concrete base.
Similarly, if existing walls have to be rendered it is possible to apply ARDEX AM 100, a proprietary cement-based render that will allow the fixing of ceramic tiling after only 2 hours. This will only be effective if the wall is of a suitable construction, e.g. concrete blockwork, and clearly is adequately mature and dimensionally stable.

Adhesive performance
The adhesives should be selected on the basis of the most appropriate characteristics to suit the circumstances on site. With floor tiling it may be particularly important for the installed ceramic tiling to be able to carry foot traffic a few hours after fixing. In these circumstances the adhesive used will need to have the properties of a short setting time, rapid hardening and rapid strength development, for instance ARDEX S 16 rapid drying tile and natural stone adhesive is particularly suitable for this type of application in dry locations and will allow grouting and foot traffic within a few hours. If the time period between fixing and carrying traffic is longer, e.g. 5 hours plus, then a normal setting but rapid hardening adhesive with early strength development such as ARDEX-FLEX S 38 flexible floor tile bedding mortar will be suitable.
These criteria will have to include consideration of other required characteristics, e.g. communal showers, where the ceramic tiling will be exposed to wet conditions and will require the adhesive to be water-resistant (e.g. ARDEX-FLEX 6001 or ARDEX-FLEX S 38); where translucent materials, such as glass mosaics are to be fixed, a white adhesive such as ARDEX S 16 W rapid drying tile adhesive will be required.
A further consideration is that the adhesive must also perform in the long term. Enhanced adhesive performance will also help to minimise risks of failure at a later date, as any stresses that were unforeseen at the time of installation or were generated as a result of the fast track working are more likely to be accommodated.
In addition sensitive backgrounds such as timber-based boards or moisture sensitive natural stones will also require an adhesive that is rapid drying as well as rapid hardening. The latter two terms are often confused but are very different.
A true rapid drying system such as those featuring ARDEX Rapidry Formula technology, will dry by chemically binding any free water into stable hydration reaction products so that the material will dry even between two non-absorbent surfaces and irrespective of application thickness. The free water does not need to evaporate away.

Grout performance
Typically, grouting must wait for 24 hours after fixing the tiles; 48 hours in the winter; even longer for swimming pools; these times can be reduced significantly by using rapid hardening adhesives as discussed above.
The grouting of tile joints should commence as soon as possible after the ceramic tiles are fixed and the adhesive has hardened sufficiently so that the empty joints do not collect dust and other extraneous materials. The rapid setting and hardening adhesives will allow the grouting to commence in as little as 2 hours after fixing but if the grouted ceramic tiling has to be trafficked as soon as possible the grout mortar will also have to harden rapidly.
The cement-based grout mortars can have rapid setting and rapid hardening characteristics to enable the ceramic floor tiling to be trafficked in as little as 1½ hours after the completion of grouting. Suitable products include ARDEX-FLEX FL and ARDEX GK grouts that are not only rapid hardening but are also suitable for heavily trafficked locations such a shopping malls, etc. The installation of finishes takes place towards the end of any contract and is particularly important with ceramic floor tiling as there should be provision for temporary protection of the completed tiling if other trades will be working in the same area.

Typical situations
Repairs to or the installation of ceramic tiling in occupied premises will frequently be to mature backgrounds so that the constraints of drying shrinkage are not present or can be overcome by the techniques outlined above. The adhesives and grouts used to install the ceramic tiling should enable the ceramic tiling to be fixed, grouted and put into use with the minimum delay. Rapid hardening adhesives and grouts are generally the preferred products for ceramic floor tiling, whilst ceramic wall tiling is less critical but the products selected have to perform adequately to ensure completion is not delayed.
Some refurbishment and repairs in public areas require all of the products used to install the ceramic tiling to set and harden rapidly so that full use can be made of the area within a short period of time. Examples include public transport systems, fire stations, airports, retail outlets and similar locations where work has to be carried out during a very short time period and the facility brought back into use within a few hours. Here the adhesives and grouts used have to set, harden and gain strength very rapidly so that the public can have unimpeded use of the facility. In these critical areas the installation has to be right first time, as the consequences can be considerably embarrassing if the installation fails to perform adequately.
Note that repairs to existing tiling will frequently not match the existing tiling due to wear and dirt deposition. The grouting can also appear different in colour as subtle differences in site conditions can cause slight colour differences. These tend to become less noticeable with time for floors as the surface is trafficked.
The use of tile and grout cleaning systems can also help, particularly for wall tiling.

Conclusion
The options have to be carefully considered and the design has to take into account the environment where the tiling has to be installed, the backgrounds to be tiled as well as any requirement for early trafficking or use. Fast track installation of rigid floorings is possible, and can be very cost effective, when appropriate materials and techniques are specified and used.

Email: info@ardex.co.uk