How to level a floor

What is a self-levelling compound?

Self-levelling concrete is a polymer-modified cement that has high flow characteristics, it’s used in the preparation of laying most floor coverings to create a smooth and level surface.

Levelling compound can be used on a variety of substrates including concrete, screed, existing tiles, and timber floors. Ideal for using in areas where the floor dips or needs filling in. Due to the nature of self-levelling compound, excessive amounts of water are not needed.

In this article we take you through the process of using a self-levelling compound, whether you are wanting to know how to level a concrete floor or how to level a wooden floor, the general application process is the same, it’s just the product that differs. To see the range of levelling products available, read our helpful guide.

Here’s our quick how-to video to show how best to level a floor.

How to self level a floor

Preparing the Substrate

Subfloors should always be primed. The substrate must be clean, dry and free from dust, laitance and any other contaminants which may act as a release agent, preventing the leveller from bonding to the surface.

This includes the removal of existing floor paints, low strength smoothing compounds, old flooring adhesives, surface laitance and any materials that may hinder adhesion.

Highly polished surfaces should be mechanically abraded to give a lightly textured surface to key to.

The BAL Primer should be allowed to dry prior to the application of the self-leveller. Drying times will be based on the ambient conditions, bear in mind that cold or damp/humid conditions, or poor airflow, can extend the drying time.

Mixing and Applying

When mixing a self-levelling compound, the powder and water mixing ratios should be controlled. Avoid adding any excess water as this will greatly affect the surface finish, curing and drying times.

Always use clean cold water as warm water will greatly affect the product’s working and open time.

Pour the recommended volume of water into a clean, oversized bucket (minimum 20 litres) and gradually add the levelling powder whilst mixing continuously with an electric drill with a mixer attachment.

When all the powder is added, mix for a further 2 minutes keeping the whisk below the surface (to minimise air entrapment) until a lump free consistency is attained. Once mixed, the product can be applied by pouring it onto the floor and spreading with the smooth edge of a steel trowel.

Plan to begin at the furthest point working back towards the point of entry to avoid walking through the wet product. Maintain a wet edge to ensure adjacent mixes blend in correctly. For large areas or deep areas, it may be beneficial to batten off areas into sections.

A spiked roller must be used on the newly laid screed to release trapped air bubbles, preventing them from curing on the surface. If a spiked roller is not used, air bubbles will form on the surface and will ruin the finish of the smooth leveller, it may also cause lifting or cracking further down the line.

Curing and Drying

Whilst curing, ensure the space is free from floor traffic and create good room conditions where possible (i.e. air temperature of 20°C, air humidity of 75% maximum and good ventilation).

Cold, humid or damp rooms, or those with poor airflow, will prolong curing and drying times, so make adequate allowances for such. It’s advised to avoid strong through drafts and direct sunlight during the curing process as this can ‘force dry’ the product, affecting the surface cure and may result in excess tension, surface crazing and cracking.

Underfloor Heating

All Ultra Levelling compounds are suitable for use on floors with in-screed underfloor heating.

If using directly over the top of underfloor heat matting, we recommend you use Ultra-Level It Two 2-Part latex. The added latex polymers adhere to the matting surface which prevents it separating from the levelling compound.

Our guide on how to level a floor is pretty straight forward so here’s a quick recap.

Clean your substrate of any dirt and debris, prime it and then carefully mix your compound using only cold clean water. Whisk the mixture of powder and water to a lump free consistency and then apply to your surface using a steel trowel, followed by a spiked roller. Finally, allow the floor to dry naturally to avoid cracking.

Once your floor has completely cured, it’s time to start your floor tiling!