Is it Possible to Pour Self-Levelling Compound Over Tiled Floors Without Priming?
Yes, under certain circumstances, you can apply a flexible self-levelling compound directly over existing tiled surfaces without the need for a primer. This approach is suitable when using specific types of self-levelling mixes designed for such applications. The key is choosing a product that inherently adheres well to tiles and offers flexibility after curing, reducing the risk of cracks or delamination.
Choosing the Right Self-Levelling Compound
Opt for a 2-part latex-based self-levelling compound. Typically, these come in a pre-measured package: a bag of self-levelling cement and a tub of latex, which are mixed together in a fixed ratio. This eliminates the need for manual measurement or mixing ratios, ensuring consistent quality and performance. When mixed, these compounds flow smoothly around the floor, creating a professional finish with minimal effort.
Preparation of the Tiled Surface
Before application, it’s essential to ensure that the tiles are in good condition. The surface should be thoroughly swept or vacuumed to remove dust, dirt, or debris. The tiles must be completely dry, as moisture can hinder adhesion and curing. If the existing tiles are loose or starting to lift, it’s advisable to remove them entirely before proceeding. Applying self-levelling compound over unstable tiles can lead to uneven surfaces and future failure.
Calculating Material Requirements
Standard 20kg bags of self-levelling compound typically cover approximately 2.5m2 at a thickness of 5mm. To determine how much material you’ll need, measure the room’s length and width to find the total area, then divide by the coverage per bag. For example:
- Room Dimensions: 4m x 4m = 16m2
- Number of Bags Needed: 16m2 / 2.5m2 = 6.4, rounded up to 7 bags
It’s prudent to purchase a few extra bags to account for any unforeseen issues or thicker pours. Running out mid-application can result in ridges or uneven surfaces, which are difficult to rectify once cured.
Considerations for Ground Floors and Subfloor Conditions
If your tiles are laid on a solid, stable ground floor with minimal movement, you might consider using a cement-based self-levelling compound mixed with water. However, this option is limited to areas without structural movement, as cement/water mixes are not flexible and are prone to cracking under stress. The latex-enhanced self-levelling compounds are more versatile, suitable for ground and upper floors, and accommodate slight movements without cracking.
Priming and Surface Preparation for Cement/Water Mixes
When opting for a cement/water-based self-levelling compound, proper priming of the existing tiles becomes crucial. Use a primer such as SBR (Styrene-Butadiene Rubber) or an equivalent to enhance adhesion. Additionally, creating a mechanical key can improve bonding; this can be achieved by scoring the tile surface with a diamond disk attached to an angle grinder. This roughens the surface, providing better grip for the cement mix. Keep in mind that this process generates dust and requires proper safety precautions.
Application Tips and Final Advice
For smaller areas, the latex-enhanced self-levelling compounds are easier to spread and more forgiving, as they flow better and adhere well to the tiles. In large areas, cement/water mixes can be effective if thorough preparation is undertaken. Be prepared for more manual troweling to achieve a flat surface, as these mixes do not flow as effortlessly as their latex counterparts.
In summary, pouring self-levelling compound directly over tiled floors is feasible with the right product and preparation. Selecting a flexible, latex-based compound simplifies the process and ensures a durable, even surface suitable for subsequent flooring layers.