We know you can have questions about our products. Our Technical Services team have advised on thousands of them, and you can find answers to the more common queries here. For the latest technical or health and safety data on all ARDEX products, consult the relevant technical or health and safety datasheet on our product pages.
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NOTE: In addition to our guidance on this page, tiles should be installed in accordance with the relevant parts of BS 5385 and BS 8000: Part 11 Workmanship on Building Sites.
Before tiling to an anhydrite (or gypsum or calcium sulphate) screed, you must first ensure it is dry. They generally dry at a rate of 1 day per mm of screed thickness for depths up to 40mm, and an additional 2 days per mm for thicknesses thereafter. For example, a 40mm deep screed requires 40 days to dry and a 50mm deep screed requires 60 days. To be sure it is dry, test the screed with a hygrometer meter such as the TRAMEX Hygrohood; readings of 75% RH or lower will mean it’s ready for tiling.
After confirming it is dry, abrade the surface with suitable mechanised equipment to remove any laitance, loose debris and dust, and reveal the aggregate underneath.
The anhydrite screed should then be primed with a single coat of ARDEX P 51 diluted 1:3 with water, applied in one continuous coat using a brush or broom. Once the ARDEX P 51 is dry, tile as normal using an appropriate ARDEX Cement-Based Tile Adhesive.
Sand and cement screeds and concrete can be highly porous and absorb moisture from subsequently applied levelling compounds, which reduces their flow properties.
Before tiling onto sand and cement screeds and concrete, prime with single coat of ARDEX P 51 diluted 1:3 with water for sand and cement screeds or 1:2 for concrete and applied with a brush or broom. Once the ARDEX P 51 is dry, it can be levelled with an appropriate ARDEX Levelling Compound and then tiled with an ARDEX Cement-Based Tile Adhesive.
If levelling isn’t required, prime existing tiles with a single coat of ARDEX P 4 applied with a short pile roller or paint brush. It will dry after 30-60 minutes, producing a textured-grip surface which can then be tiled as normal using an appropriate ARDEX Cement-Based Tile Adhesive.
If levelling is required on floors, level over existing tiles with ARDITEX NA applied 3mm+ deep direct (without priming) with a smoothing trowel. It will dry in as little as 3 hours, and can then be tiled as normal using an appropriate ARDEX Cement-Based Tile Adhesive.
If levelling isn’t required, prime plywood floors with a single coat of undiluted ARDEX P 51 applied with a brush or broom. Once the ARDEX P 51 is dry, it should then be tiled using an ARDEX RAPIDRY FORMULA adhesive such as ARDEX MICROTEC X 7001, ARDEX MICROTEC S 27 or ARDEX MICROTEC S 28.
If levelling is required, level over the plywood with ARDITEX NA applied direct (without priming) with a smoothing trowel. It will dry after 3 hours and should then be oversheeted with a suitable mechanically fixed tile backer board, which can then be tiled as normal using an appropriate ARDEX Cement-Based Tile Adhesive.
Tiling to plywood walls is no longer recommended under BS 5385-1:2018. Plywood walls should be oversheeted with tile backer board or plasterboard as appropriate for the intended area, and these can then be tiled as normal using an appropriate ARDEX Cement-Based Tile Adhesive.
To tile steel in internal and external locations, including wet areas, use ARDEX X 60 PU FLEX applied direct (without priming). It will dry in 3 hours and can then be grouted using an appropriate ARDEX Tile Grout.
Uncoupling membranes with cavities can be pre-filled to produce a flat surface ideal for tiling. For this application, smooth over the uncoupling matting with ARDITEX NA up to the top of the cavities using a smoothing trowel. ARDITEX NA can be applied thicker if additional levelling is required, but along with the subsequent tile adhesive application, the depth should not exceed 10mm. ARDITEX NA will dry in as little as 3 hours and can then be tiled as normal using an appropriate ARDEX Cement-Based Tile Adhesive.
As per BS 5385, the maximum weight restrictions for wall substrates are:
Gypsum plaster: 20kg/m2
Gypsum plasterboard (12.5mm thickness): 32kg/m2
Sand and cement rendering: Generally no restrictions
Lightweight foam-cored tile backer boards: 60kg/m2
Glass reinforced cement-based boards: 50kg/m2
Gypsum fibreboards: 40kg/m2
Other rigid tile backer boards: Consult manufacturer
As per BS 5385, the following drying times should be allowed before tiling:
Concrete: at least 6 weeks
Traditional sand and cement screeds: at least 3 weeks
Traditional sand and cement renders: at least 2 weeks
Plaster: at least 4 weeks
These backgrounds shrink as they dry; to avoid the risk of debonding, tiles should be fixed after these times.
Alternatively, drying times can be significantly reduced when ARDEX Screed Cements and Renders are used in the construction process. For example, ARDEX AM 100 Render can be tiled after 2 hours and ARDEX A 38 Screed after 4 hours!
*Does not include swimming pools
Wet areas should be waterproofed before tiling using ARDEX WPC to protect moisture-sensitive backgrounds behind the tiles, and also prevent moisture-ingress into adjacent rooms. Holes, gaps and joints should be waterproofed using a slump-free mix (MIX ONE) applied with a trowel, which will dry in approximately 1 hour. Overall surface waterproofing can then be achieved with two coats of a flowing/paintable mix (MIX TWO) applied with a paint roller or brush, with 30 minutes allowed between each coat. The second coat will dry in approximately 60 minutes, and can then be tiled as normal using an appropriate ARDEX Cement-Based Tile Adhesive.
*Does not include swimming pools
The underlying substrate in wet areas, or substrates adjoining wet areas, is often moisture-sensitive e.g. plaster, plasterboard and even some proprietary tile backer boards. Even when they’re tiled, water can still get to the background through cementitious grout joints and adhesive bedding, as they’re porous in nature and allow moisture to be absorbed through them. Ultimately, this results in damp and mould; and over time, it can transfer to adjoining rooms and/or cause the tiles to de-bond. As recommended by BS 5385-1: 2018 and BS 5385-4: 2015, ensure wet areas in both domestic and commercial installations are waterproofed (we recommend ARDEX WPC) to prevent unsightly and costly water damage.
Ready-mixed tile adhesives should only be used to fix mosaics and ceramics up to 300mm x 300mm or porcelain up to 150mm x 150mm. Today’s popular large format tiles can measure 600mm x 300mm or bigger, so ready-mixed tile adhesives should not be used to fix them. Instead, use an appropriate ARDEX Cement-Based Tile Adhesive.
Ready-mixed tile adhesives should only be used to fix wall tiles. Floor tiles should be fixed with an appropriate ARDEX Cement-Based Tile Adhesive.
Today’s large format tiles are not only heavy, but also very dense and can have flat undersides too, making it more difficult for traditional adhesives to grab them. To stop your tiles slipping, fix them with an advanced slip-resistant tile adhesive. ARDEX MICROTEC X 77 for example achieves double the European Standard for slip resistance and can be used to fit all tile sizes without slipping (consideration must still be given to the BS 5385 fixing guidance e.g. when fixing tiles at height).
With standard tile adhesives, you may find there’s not enough time to cut and install your tiles, and so you must remove your applied adhesive and replace it with freshly mixed material; or your adhesive has simply gone off in your bucket and you need to throw it away and mix a fresh batch. This is particularly common in summer, with higher temperatures causing them to skin over much quicker. To reduce waste of skinned over tile adhesive, use one with an extended pot life and open time for better longevity from the very outset. ARDEX MICROTEC X 77 for example has a pot life of 3 hours and an open time of 60 minutes!
When tiling to sand and cement screeds and concrete, the substrate can be dampened with water using a mist sprayer. This will reduce suction from the substrate, and help maintain the open time of all ARDEX Cement-Based Tile Adhesives.
Under BS 5385, solid bed fixing must be achieved for: all floor tiling; wall tiling with tiles greater than 0.1m2 (316mm x 316mm); and all tiling in all wet, external or swimming pool locations. To ensure you’re achieving solid bed fixing on floor tiles, use a semi-pourable or pourable tile adhesive such as ARDEX X 7 R, ARDEX MICROTEC X 78 or ARDEX MICROTEC X 7001. To ensure you’re achieving solid bed fixing on walls, or when using a slump-free adhesive on floors, back buttering may be required.
To stick down uncoupling membranes such as those by Schluter and Dural, use ARDEX AF 200 PLUS. It is ready-mixed and can be applied using a B1 or 2mm x 6mm v-shaped notch trowel direct (without priming) to plywood, floorboards and dry concrete, as well heated and unheated sand and cement screeds and levelling compounds. After 5-10 minutes, the matting can be installed and then tiled or levelled immediately using an appropriate ARDEX Cement-Based Tile Adhesive or ARDEX Levelling Compound.
Pot life is also known working time, and they both refer to the length of time that the mixed mortar remains usable and workable inside the pot/bucket after it has been mixed.
Open time is the length of time that tile adhesive ribs remain wet and able to receive tiles (before skinning over) after being spread onto the wall or floor.
Adjustment time is the amount of time in which a tile can adjusted or moved after it has been fixed into the freshly applied tile adhesive.
Efflorescence is a naturally occurring and well-documented issue, affecting many cement-based products (not just tile grouts) due to their water and soluble lime content. It happens during the drying phase, with the soluble lime depositing on the surface as a dry white powder as the water evaporates. In tiling, the moisture can come from the tile grout, adhesive bed, underlying substrate and even the atmospheric conditions of the room!
Efflorescence is aggravated by excessively damp conditions after installation and by prolonged delays in drying out. The modern trend of large format tiles means there are now fewer grout joints over the tiled area and drying is slowed; it is therefore not unexpected for efflorescence to occur.
Efflorescence cannot be avoided; however, steps can be taken so as not to exacerbate the problem: 1) Do not exceed the water requirements of the tile grout 2) Do not use excessive water during cleaning down and 3) Warm and dry conditions following installation will assist the drying process.
Fortunately, where you do experience efflorescence, it can be removed easily using an appropriate proprietary cleaner designed for this purpose.
Tile grouts can have a significant impact on the resulting aesthetic of both the tiles and the room. The ARDEX-FLEX Tile Grout range is available in 35 colours to suit any installation; and whether you’re looking to complement or contrast with the tiles, free colour stick samples can be ordered online so you can test the look before purchasing.
Traditional epoxy tile grouts can quickly stick to the tile face, and as a result many tilers clean them off too early to prevent this from happening, which often results in some of the soft grout mortar coming out of the joints. Alternatively, ARDEX EG 8 PLUS Epoxide Tile Grout can be left on the tile surface for up to 60 minutes, allowing the grout to harden adequately, and can still be cleaned off with a normal sponge! For best results, use a fine mist spray to soften the residues first.
To prevent mould growth in silicone sealants, use one that contains a fungicide such as ARDEX ST.
The main issue associated with fixing natural stone is determining if they’re moisture-sensitive or not and, following that, using the correct products to fix them. If the stone is moisture-sensitive, moisture from traditional adhesives and grouts can migrate into the stone and cause discolouration, staining and even warping. If you’re fixing moisture-sensitive stone, or if you’re unsure, use an ARDEX Natural Stone Tile Adhesive and ARDEX MG Tile Grout. These products incorporate ARDEX RAPIDRY FORMULA Technology to ‘lock’ the mix water within the mortar and eliminate the risk of water staining. The installation should then be finished with ARDEX ST Silicone Sealant.
As per BS 5385, the mesh-backing on the tile must be removed, e.g. using a grinder, so that no more than 25% of the back of the tile is covered with the mesh. The tiles can then be fixed using the appropriate ARDEX Natural Stone Tile Adhesive. If the mesh cannot be removed, the stone should be mechanically fixed (on both walls and floors, as per BS 5385).