How to Tile onto a Concrete Base
Whether you're fixing Ibiza Bianco honed marble tiles, or large format Amiata Gris stone effect porcelain tiles, you need to assess whether your substrate is concrete and prepare it suitably to ensure your tiling project is a success.
What is your substrate made of?
If the tiling surface you're faced with clearly isn't wood, it may be a sand and cement screed, calcium sulphate (anhydrite) screed, or concrete 'slab' floor. Generally, concrete floors are thick foundation slabs of approx 150mm, whereas a screed (sand and cement or anhydrite) will be laid on top of a concrete floor.
Is concrete the same as cement?
No, cement is an ingredient of concrete. Concrete is made of cement (a very fine powder made from limestone, sand, clay, and iron ore), and aggregates.
If you're tiling in an area where moisture is present and inevitable, such as cellars, a damp proof solution may be required. If you choose to fit a traditional plastic damp proof membrane, a screed will need to be laid before you can proceed with fixing your floor tiles.
An alternative option that doesn't require a screed and enables you to fix floor tiles directly onto a concrete base is Tilemaster FAST One Coat DPM, an epoxy-based fast curing surface damp proof membrane.
5 key considerations before fixing floor tiles to concrete floors:
1. Is the concrete dry? If the concrete is new, the general rule is to allow a drying time of 1 day for every 1mm thickness. For new and old cement floors it's prudent to perform a moisture test. We always recommend the use of a decoupling membrane on new concrete floors, even if they appear to be dry.
2. Is the concrete damaged? Damaged concrete should be replaced. Cracked concrete should be filled, or a suitable anti-fracture matting such as Kerakol Idrobuild Tex should be fitted.
3. Is the concrete surface free from contaminants? Dust and dirt should be removed from old concrete surfaces. New concrete floors may have laitance - a surface layer of fine particles displaced as water evaporates that should be mechanically removed.
4. Is the concrete floor flat, level and smooth? An even and consistent surface will make fixing floor tiles easier and quicker. To solve any issues with uneven concrete bases a self-levelling screed can be used.
5. What primer should you use? The use of a bonding agent such as Kerakol Primer A is key to ensuring the adhesive can perform to its optimum. We don't recommend using PVA as a primer.
If you have an area of flooring that is part concrete and part wood read our article about tiling onto wooden floors where you can learn how wood and concrete need different preparation before you commence tiling.
In conclusion, lack of attention to the preparation of your substrate may result in the floor tiles splitting or detaching from the adhesive.