20d (edited) • Recipes
Basic Cob building recipe
Natural building material using clay, sand, and straw for walls, ovens, and benches
Recipe Details
### Materials Needed:
- Clay soil (from subsoil layer)
- Sharp sand (angular, various sizes)
- Long straw (wheat, rice, oat)
- Water
- Mixing tarp (6'x8' minimum)
### Basic Recipe Ratios:
- Clay soil: 15-30% of total volume
- Sand: 70-85% of total volume
- Straw: Added "to taste" after mixing
### Tools:
- Wheelbarrow
- Buckets for measuring
- Tarps for mixing
- Hoe for initial mixing
### Instructions:
1. **Test your soil**: Perform jar test to determine clay content
2. **Prepare clay**: Soak clay soil overnight in buckets
3. **Mix dry ingredients**: Combine clay and sand on tarp
4. **Add water gradually**: Create well in center, add water slowly
5. **Mix by foot**: Dance/stomp on mixture, rolling with tarp
6. **Form "burrito"**: When mix holds together when rolled in tarp
7. **Add straw**: Sprinkle chopped straw evenly, mix in by foot
8. **Final consistency**: Should be plastic, not sticky or crumbly
### Tests for Readiness:
- **Ball test**: Forms ball when squeezed, minimal cracking
- **Drop test**: Ball maintains shape when dropped from waist height
- **Straw content**: Each handful should have long fibers throughout
### Applications:
- Wall building (coil method)
- Mortar for stone walls
- Earth ovens and rocket stoves
- Garden benches and raised beds
### Curing:
- Allow to dry slowly (cover with damp cloth)
- Avoid direct sun and wind initially
- Full cure takes 4-6 weeks depending on thickness
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Basic Cob building recipe
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