Yes, in many cases self-levelling concrete can be applied over an existing concrete slab, provided the base is stable and in good condition. Self-levelling screed is a polymer-modified mixture that spreads easily across the floor, filling dips and uneven areas before setting into a smooth surface. It creates an excellent base for tiles, wood flooring, or vinyl and often cures faster than traditional screeds. Because it can be installed in very thin layers, usually only a few millimetres thick, it can remove the need to break out the old concrete. When installed correctly, it is durable, cost-effective, and works well with underfloor heating systems.
When it’s a good idea (and when it isn’t)
A levelling overlay works best when the existing slab is structurally sound but slightly uneven. Minor cracks, shallow dips, and worn surfaces can usually be corrected using self-levelling screed. It may also be applied over concrete, tile, or plywood if the surface is solid and properly prepared.
However, it should not be used to hide serious structural problems. Large cracks, movement, subsidence, damp issues, or water damage should always be addressed first. During a survey, londonfloorscreeding.co.uk assesses the slab carefully and advises if grinding, deeper screeding, or repairs are required.
Preparation (this is what makes it last)
Proper preparation is essential for long-term performance.
- Thorough cleaning: remove dust, grease, paint, and adhesive residue.
- Repair defects: fill cracks, holes, and damaged areas.
- Create surface texture: grind or scarify smooth concrete to improve bonding.
- Prime the surface: vacuum dust and apply a primer recommended by the manufacturer.
Application basics
Most products are supplied in 20–25kg bags that are mixed with water before pouring. Because the mixture sets quickly, it must be applied without delay. Installers spread the compound using a gauge rake to control thickness and a spiked roller to release trapped air.
Self-levelling screed is usually applied between 2–5mm thick, compared with around 35–50mm for traditional screed. Many products can be walked on within 24–48 hours and are ready for flooring once fully cured.
Cost and next steps
DIY materials for a small room may cost only a few hundred pounds. Professional installations vary depending on project size and location, with labour in London often around £10–£12 per m² for basic levelling.
A professional survey provides the most accurate price. londonfloorscreeding.co.uk offers clear advice, accurate measurements, and straightforward quotations so your floor is level and ready for final flooring.