What's the Difference?
Topsoil is the uppermost layer of natural earth — typically the top 200-300mm. It contains minerals, organic matter, and microorganisms. Good topsoil is the foundation for any garden.
Compost is decomposed organic matter — garden waste, food scraps, or commercially produced from green waste. It's a soil improver, not a replacement for soil.
When to Use Topsoil
- Before laying turf — if your existing soil is poor, compacted, or full of rubble, a 50-100mm layer of quality topsoil gives turf the best start
- Raising levels — filling low spots, building up borders, or creating new beds
- New builds — construction sites often have subsoil at the surface with all the topsoil stripped away. You need to bring in fresh topsoil before any planting or turfing
When to Use Compost
- Improving existing soil — dig compost into clay soil to improve drainage, or into sandy soil to improve moisture retention
- Mulching borders — a 50mm layer of compost on top of beds suppresses weeds, retains moisture, and feeds plants as it breaks down
- Potting mixes — compost is a key ingredient in container growing
Can You Use Compost Instead of Topsoil?
No. Compost alone is too light and nutrient-rich for turf — it dries out too quickly and can scorch grass roots. Always use proper topsoil as the growing medium and mix in compost as an improver if needed.
What to Look For in Quality Topsoil
- BS 3882 certified — the British Standard for topsoil guarantees minimum quality
- Screened to 10mm — removes stones and debris
- pH between 5.5 and 7.5 — suitable for most plants and turf
- Free from perennial weed roots — poor topsoil introduces weeds to your garden