Tiles can experience a lot of stress due to movement in the substrate, foot traffic and thermally-induced expansion and contraction that can come from underfloor heating. A flexible tile adhesive can absorb some of this stress and help reduce the chances of your tiles cracking – the more flexible the adhesive, the more peace of mind you have.
A tile adhesive with an 'S' classification means it has a higher degree of flexibility in comparison to standard tile adhesives. Each classification describes how much an adhesive will deform — or bend — in order to accommodate a limited amount of movement after fixing tiles.
Extra Flexible Tile Adhesives (S1)
S1 tile adhesives are deformable and withstand deflection of more than 2.5mm and less than 5mm.
In general, an S1 tile adhesive will be suitable for most applications, such as fixing all types of ceramic wall and floor tiles, mosaics, marble, terrazzo and natural stone to most wall and floor substrates – this includes plywood, anhydrite screeds and power floated concrete. You can also use an s1 tile adhesive when tiling onto underfloor heating as it will withstand the expansion and contraction of the substrate.
Products like weberset SPF or weberset rapid SPF are particularly suited for situations where some movement, deflection or limited shrinkage is likely. An added benefit of weberset rapid SPF – aside from it including weber's Low Dust Technology™ – is that it allows for light foot traffic after two hours. A full load is possible after 24 hours.
Ultra Flexible Tile Adhesives (S2)
S2 tile adhesives are deformable and withstand deflection of more than 5mm, essential in areas subject to lots of vibration or movement.
Our best flexible tile adhesive for wooden floors and tiling heavy or large tiles onto floors is weberset pro lite – rapid, a lightweight, rapid-setting (2 hours), ultra-flexible cement-based adhesive. Used to fix all ceramic tiles, porcelain, mosaic, quarry, marble, terrazzo and natural stone, it can also be used to tile onto suspended wooden floors.
The best solution for tiling onto walls where more vibration and movement is likely — or for tiling large format tiles onto walls — would be to use weberset plus mixed with weber AD250, a synthetic water-based admixture that disperses highly flexible acrylic polymers when added to standard adhesives. Replacing the need for water, it strengthens the bond of the adhesive and eradicates the need for a primer.
Another benefit of using weber AD250 when added to weberset plus is that it provides the strength and quality of an s2 tile adhesive – like weberset pro lite – rapid – but it's not fast-setting so it gives you more time to complete any larger projects you're working on.