An earthen floor sounds like poverty. In practice — it's elegant: warm, hard, beautiful, free.
Mix
Clay (binder) + sand (strength) + straw (reinforcement). Ratio: 1 part clay, 3 parts sand, some chopped straw. Test: roll a ball, dry it — shouldn't crack (too much clay) or crumble (too little).
Installation
Base: compacted gravel 10–15 cm (drainage). First layer: rough mix 7–10 cm. Dry 1–2 weeks. Second layer: fine mix 2–3 cm. Dry. Sand smooth.
Finish
Soak with linseed oil (3–4 coats with drying). Oil polymerizes — surface becomes waterproof and hard. Final coat: linseed oil + beeswax = shine and protection.
Result
Floor is warm (earth doesn't chill like concrete). Hard (no dust after oiling). Beautiful (warm terracotta color). Repair: fill cracks with the same mix, re-oil. Cost: $0 (all materials from the property).