When you are ready to tile your floor, the choice of floor tile adhesive will be an important factor if you want to avoid any failures or potential issues. There is only one type of adhesive you should consider for using on a floor and this is cement based adhesive or thinset adhesive which you will have to mix with water or a polymer in a bucket before using it to fix your tiles. I know you are thinking right now “But I really want the convenience of a ready mixed tile adhesive and I’ve seen one suitable for floor tiling in my local d.i.y centre” Indeed, there are ready mixed tile adhesives that are marketed as a solution for floor tiling, but you really, really, really want to avoid using them (I hope that’s enough really’s to put you off)
All ready mixed tile adhesive whether it be manufactured for use on walls or floors dries through process of dispersion, so it needs to air to be able to dry out and stick the tiles. This works ok with relatively small ceramic tiles (which are porous) on walls, where the adhesive is only about 2mm in thickness and can dry out in good time. Floor tiles are generally made of materials that are more dense than standard ceramic and are typically vitrified or full-bodied porcelain, this is because you need a stronger material for use where you will walk on the tiles. The side effect of a tile being more dense is that it will have a lower porosity and therefore a ready mixed adhesive will have trouble curing as it cannot dry into the body of the tile. Partner this with the larger size of tiles used on a floor and a greater thickness of adhesive required and you have adhesive which can potentially still be wet after 7 days, which is certainly not suitable on a floor which needs to be walked on relatively quickly.
Cement based adhesive dries through a hydraulic process and will dry whether it be under a totally non porous tile or even under water (in certain circumstances) It can be used to thicknesses of 25mm and available in white or grey colour and also in different setting types. A professional will typically use a rapidset cement based adhesive on a floor to allow fast grouting once tiling has finished and also allows foot traffic after about 3 hours or so. The pot life (or life of product once mixed with water) is only about 30 minutes, so be wary that if you mix a whole 20kg bag in one go, you won’t have long to use it, this can be even less time on a hot day. A standard setting cement based adhesive will have a curing time of approx 24 hours, but now the pot life has been extended to 4-5 hours from 30 minutes, which is much more forgiving and suitable for d.i.y tilers. Most people would use a standard setting adhesive on a wall as the need for fast cure is not there and there are potentially more cuts and awkward tile fixing on walls, but this is not a hard and fast rule.
Choose a white cement based adhesive if tiling with a light coloured natural stone and make sure that 100% coverage of adhesive is achieved behind the tile so there are no visible gaps through the tile, this is also true of glass tiles of course. A white adhesive should be used also if you are grouting with a light colour such as ivory or white as grey could potentially stain the grout, but if your work is clean then there is no issue with this. A grey cement based adhesive should be selected for most floor tiling with porcelain or ceramic tiles, or with tiles that will grouted with dark colours on a wall. White adhesive is always more expensive than grey adhesive , so choose your adhesive wisely.
Flexible Floor Tile Adhesive
You will need to select a flexible cement based adhesive if any of the following apply to your tile installation:
- You are using glass or porcelain tiles or other low porosity tiles
- You have a suspended floor (usually wooden)
- You have underfloor heating system installed
- The substrate has a lower porosity
- Any area subject to some limited movement
Flexible floor tile adhesive will not be able to prevent tiles from debonding or cracking if the movement in the floor is too severe, this is because tiles are a rigid finish and are not able to bend, please refer to our page on bathroom floor tiling for more information on how to prepare a floor for tiling.
There are varying degrees of flexible cement based adhesives available, some are suitable for tiling onto chipboard floors as well as marine grade plywood, these are usually a 2 part rubber crumb adhesive which are quite expensive, but offer the most comprehensive solution onto suspect substrates.
Thick Bed Floor Tile Adhesive
If you have larger tiles for your floor, or anything above 400mm x 400mm then you should consider using a thick bed tile adhesive. These adhesives are designed to be used up to 25mm thick, whereas a standard cement based adhesive can be used up to about 8mm maximum. Being able to go up to 25mm thick allows for larger tiles which are difficult to bed into standard adhesive beds to be solid bed fixed without the need to keep back buttering the tiles. You need to invest in a large format trowel to get the best advantage from using these type of adhesives, but they can be a real time saver, especially the ones that can be poured from the buckets when first mixed and then solidify over the next few minutes to allow for the trowelling of the adhesive. People have traditionally used blobs of adhesive under a tile to get the correct levels in the tiled finish, but this is a weakness that can lead to cracks from the voids in the tiling and can cause serious issues when using a translucent stone and the blobs or dot and dabs are visible through the tiles. There is no excuse for not achieving a 100% or close coverage under tiles, especially now that thick bed adhesives are available.
If you have any questions or comments in regards to this article, then please post in the comment section below.