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BioDome

Frame & Roof: Wattle Basket and Da Vinci Bridge Rafters

Da Vinci's self-supporting bridge principle
Leonardo da Vinci’s self-supporting bridge: interlocking beams held together by geometry alone
Physical demonstration of Da Vinci's interlocking bridge structure
Da Vinci’s bridge built in practice — the same interlocking principle creates our A-frame rafters

Wall Framework: Wattle Basket

Section titled “Wall Framework: Wattle Basket”
  • Vertical posts: 8–10cm diameter eucalyptus, 2.5m height, 40cm spacing
  • Horizontal weavers: 3–5cm diameter, woven between verticals
  • Wattle basket structure: creates cavity for straw-clay insulation
  • Integration with gabion base: posts set into stone fill, wedged tight
  • Top plate connection: horizontal beam ties posts, receives roof rafters
  • Corner posts: heavier gauge (10–12cm), anchored deep into gabion
Lean-to roof structure showing rafter connections and purlin layout
Lean-to roof variation: rafter pairs spanning the rectangular width

Roof: Da Vinci Bridge Rafters

Section titled “Roof: Da Vinci Bridge Rafters”
  • Da Vinci bridge principle: interlocking A-frame pairs, no central ridge beam
  • Rafter sizing: 10–12cm diameter eucalyptus, 3.5m length per rafter
  • Interlocking geometry: notched laps where rafters cross, locked by gravity and compression
  • Purlin layout: 5–7cm diameter horizontal poles, 50cm spacing, support EPDM deck
  • Connection to wall plate: rafter feet notched over plate, pegged with hardwood dowels
  • Gable ends: infilled with wattle weave or fixed glazing
Double reciprocal roof structure with interlocking timber rafters
Double reciprocal roof: interlocking rafters demonstrate the self-supporting principle
Reciprocal roof during assembly showing rafter placement sequence
Reciprocal roof assembly — each rafter rests on the next, no central support needed