How Much Self-Levelling Compound Do I Need?

How We Calculated This

• Floor area: 20m²
• Average depth: 5mm
• Coverage rate: 1.65 kg/m² per mm (mid-range)
• Total: 20 × 5 × 1.65 = 165 kg
• Bags: 165 / 25 = 6.6 bags, say 7 bags of 25kg

Typical Depths

• 2–3mm: Smoothing a slightly uneven floor before vinyl or LVT
• 5–10mm: Levelling an old concrete floor with moderate unevenness
• 10–30mm: Heavy correction — use a thick-bed compound or base coat first
• 30–80mm: Deep fill compounds available but very expensive — consider screed instead

Types of Self-Levelling Compound

• Standard (cementitious): 2–10mm. Walk-on in 2–4 hours
• Thick-bed: 5–30mm in one pour. Slower to set
• Fibre-reinforced: Reduces cracking on problematic substrates
• Flexible: For timber subfloors that flex slightly

Subfloor Preparation

The subfloor must be clean, sound, and primed. Use a suitable primer to seal porous concrete and improve adhesion. On timber subfloors, use a flexible compound and ensure boards are firmly fixed with no bounce. Seal all gaps and holes to prevent the liquid compound leaking through.

Cost Guide

Standard self-levelling compound costs £15–30 per 25kg bag. For our example (7 bags), material cost is approximately £105–210. Primer adds £15–25 per 5L bottle (covers ~15–20m²).