Can you self-level onto tile?

Yes, you can pour a “flexible” self-levelling compound directly onto a tiled floor, without the need for a primer, under the following conditions:

You use a flexible self-levelling compound, these normally come with a bag of self-levelling cement and a tub of latex – in a premixed ratio. This also means you don’t have to measure out any ratios on site. One tub of latex mixes with one bag of self-levelling cement in one bucket. Easy!

If you use a self-levelling compound that mixes with water then you will need to do a few more steps to prime the floor, before you can start applying your self-levelling compound.

You ensure that the tiles are swept or hoovered clean, and dry before applying the self-levelling compound. If you are using a self-levelling compound that is mixed with a tub of latex.

This type of self-levelling compound is suitable for ground floors as well as 1st floors, where there may be some movement under the tiles. This is because the latex/cement mix offers more flexibility even after it has set, meaning it is less likely to crack.

I tend to use 2-part latex-based self-levelling compound like the one listed below as it can be used in almost any situation. The bag of self-levelling cement and tub of latex are in the correct ratio so there is no need to mix anything out. All you need to do is mix them together in a bucket. I also find that it flows better around the floor, as it is mixed with latex as opposed to water. It requires no effort to spread around the room and leaves a professional-looking finish.

The tiles should be sound and not coming loose. If the tiles are starting to come loose I would advise ripping them all up.

How to calculate how much self-levelling compound you will need

Ultra Self levelling compound comes in a standard 20kg bag and will cover 2.5m2 at a thickness of 5mm. All you need to do is calculate the Area of your room and the thickness required.

Area of Room (m2) = Length (m) x Width (m)

Bags required = Area of Room (m2) / coverage 2.5m2 @ (5mm thick)

4m x4m =24m2 24m2/2.5m2 = 9.6 bags

For a room 4m x 4m you will need 9.6, so 10 bags

It is always best to have a couple more bags than you actually need just in case you end up pouring your self-levelling compound thicker than expected. There is nothing worse than running out mid-pour and having a ridge in your floor.

If the tiles are on a solid ground floor then you might be able to use a cement-based self-levelling compound that is mixed with water. This is because there will be no movement in the subfloor. You will have to do some more work!

Cement/water-based self-levelling compound is not flexible which greatly limits its applicability. So it is only suitable for areas with no movement, i.e. ground floors. The flexible self-levelling compound you mix with latex on the other hand – can be used anywhere.

You will also need to prime the subfloor when using cement/water self-levelling compound, either mechanically, chemically or both. This is because most tiles have very little porosity especially if they are glazed, ceramic or porcelain.

If you are attempting you use a cement/water self-levelling compound you will need to be aware of the following points.

If you are using a water-mixed self-levelling compound then you should prime the floor with SBR or equivalent specific primer before applying.

If possible you should also try to create a key on the tiles, this can be done with a diamond disk in a 4″ angle grinder. The idea is to score and rough up the surface enough to provide something for the cement/water-based self-levelling compound to stick to. But this creates a lot of unnecessary dust!

I find the cement/water self-levelling compound harder to spread than the cement/latex kind. So if you have a small area to do then I would still recommend using a self-levelling compound that comes with its own tub of latex.

For large areas, a cement/water self-levelling compound will be adequate – if you do your prep. Just bear in mind you might have a bit more troweling to do to get it flat, as it does not flow as well as cement/latex self levelling compound.