The principle
Footings and cure time are non-negotiable. Posts set 600 mm deep, fittings torqued and thread-locked, and cast concrete left the full 28 days — green concrete shatters under a first lift.
Materials
- Hard plastic exercise balls
- C32/40 concrete (1.5-2 bags per stone)
- pea-shingle
- release agent
- bark mulch
Tools
- Mixer
- tub
- spade
- wheelbarrow
- wire brush
- sharp knife
Reclaimed from
Sport-equipment recyclers + Leroy Merlin + site gravel